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Ice distribution in the Gulf of St. Lawrence during the breakup season Forward, Charles Nelson 1952

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ICE DISTRIBUTION IN THE GULP OF ST. LAWRENCE DURING THE BREAKUP SEASON by CHARLES NELSON FORWARD  A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF ARTS In the Department of Geology and Geography We accept t h i s t h e s i s as conforming t o t h e standard r e q u i r e d from c a n d i d a t e s f o r t h e degree of MASTER OF ARTS.  Members o f the Department o f  THE UNIVERSITY OF BRITISH COLUMBIA September,  1952  ICE DISTRIBUTION IN THE GULP OF ST. LAWRENCE DURING THE BREAKUP SEASON toy CHARLES NELSON FORWARD  AN ABSTRACT OF A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF ARTS i n the Department  of Geology and Geography  THE UNIVERSITY OF BRITISH COLUMBIA September,  I952  2  The G u l f of S t . Lawrence Is navigation f o r nearly five  c l o s e d to commercial  months each y e a r due to i c e c o n -  ditions.  In order to lengthen the s h i p p i n g season,  greater  knowledge  of the behaviour of the i c e i s n e c e s s a r y .  A step  i n t h i s d i r e c t i o n was the i n a u g u r a t i o n i n 1$HQ o f a e r i a l surveys  i n the g u l f d u r i n g the breakup season.  have c o n t i n u e d annually f o r the past t h i r t e e n  The  surveys  years.  Based p r i m a r i l y on the d a t a p r o v i d e d by these  surveys,  maps were drawn showing the l i m i t s of the main i c e areas each breakup season.  Although the maps enabled the  of several d i s t i n c t patterns  and r a t e s  of breakup,  they  A number  were found to be important In d e t e r m i n i n g the  fundamental behaviour o f the i c e , bat factors  the  meteorological  of temperature and wind appeared to be the c h i e f  i n causing the v a r i a b l e behaviour from y e a r to In s p i t e of these v a r i a t i o n s , average c o n d i t i o n s throughout the Ice characteristics  of the i c e  season.  it  to  trace  The c h i e f  season may he s t a t e d b r i e f l y .  i c e between which l i e b r o a d s t r e t c h e s  The  covered w i t h i c e ,  i s p a r t l y covered w i t h f i e l d s  southern p a r t of the g u l f  agents  year.  I t was"possible  G u l f of S t . Lawrence i s never completely but r a t h e r ,  ocean  and wind, were examined w i t h the aim  o f d i s c o v e r i n g the causes of the breakup p a t t e r n s . of factors  variable.  influencing ice conditions, including tides,  c u r r e n t s , temperature,  in  isolation  r e v e a l e d t h a t the behaviour of the i c e was extremely The f a c t o r s  ice  of s h i f t i n g  of open water.  pack  The  i s an a r e a of accumulation where  i c e c o n d i t i o n s are most s e r i o u s .  The c l e a r i n g of i c e  from  the gulf begins slowly i n January and February and becomes accelerated in March and April.  The bulk of the ice moves  through Cabot Strait to the open Atlantic rather than remaining inside the gulf until i t melts.  Generally, the ice  either withdraws from west to east, passing through Cabot Strait directly, or i t stagnates in the southern part of the gulf toward the end of the season.  By the f i r s t of May the  gulf i s usually clear of ice which constitutes a hinderance to navigation.  TABLE OF CONTENTS CHAPTER I  INTRODUCTION The problem Sources of i n f o r m a t i o n Procedures Terminology Organization  II  PHYSICAL GEOGRAPHY S u b a e r i a l and submarine morphology Water movements and p r o p e r t i e s T i d e 8 and t i d a l c u r r e n t s Ocean c u r r e n t s Physical properties Climate Temperature Precipitation Wind Summary  III  WINTER ICE CONDITIONS December January February Summary  IV  ICE DISTRIBUTION IN THE BREAKUP SEASON DURING THE YEARS I94O-I952 INCLUSIVE Season Season Season Season Season Season Season Season Season Season Season Season Season  of of of of of of of of of of of of of  19*W  I9UM  19^2 19*1-3  I9U4 19^6  I9U7 19^-g 19^9  I95O I95I 1952  CHAPTER V  THE NATURE GP THE BREAKUP AND THE DETERMINING FACTORS P a t t e r n s and r a t e s o f breakup The determining f a c t o r s o f the breakup The n o n - v a r i a b l e f a c t o r s S u b a e r i a l and submarine morphology Tides and t i d a l c u r r e n t s Ocean c u r r e n t s Variable factors P h y s i c a l p r o p e r t i e s o f the water Meteorological factors Temperature Precipitation Wind Summary  VI  CONCLUSION  BIBLIOGRAPHY APPENDIX  LIST OF TABLES TABLE I II  PAGE Monthly Averages  of D a l l y Mean Temperature  R e l a t i o n s h i p s Between Temperature, Wind, and Ice C o n d i t i o n s  26  V  LIST OF MAPS HAP 1 2 3 4 5 b 7 S 9 10 11 12 13 14 15 16 17 IS 19 20 21  FOLLOWING? PAGE G u l f of S t . Lawrence: Place Names Submarine Contours T i d a l Ranges Ocean Currents Isotherms o f Mean Monthly Temperature Percentage Frequency of Wind Average Date of C l o s i n g of Harbour N a v i g a t i o n L o c a t i o n s of M e t e o r o l o g i c a l S t a t i o n s L i m i t 8 o f Main Ice A r e a s , Season of 1940 L i m i t s o f Main Ice A r e a s , Season of 194-1 L i m i t s o f Main Ice A r e a s , Season of 1942 L i m i t s o f Main Ice A r e a s , Season o f 194-3 L i m i t s o f Main Ice A r e a s , Season of 1 9 4 4 L i m i t s o f Main Ice A r e a s , Season of 1§45 L i m i t s of Main l e e A r e a s , Season of 1946 L i m i t s o f Main Ice A r e a s , Season of l§4-7 L i m i t s of Main Ice A r e a s , Season of 1946 L i m i t s of Main Ice A r e a s , Season of 194-9 L i m i t s of Main Ice A r e a s , Season o f 1950 L i m i t s o f Main Ice A r e a s , Season c f I95I L i m i t s o f Main l e e A r e a s , Season o f 1952  1415 1§ 21 25 27 32 40 Appendix tt  " " " • B  "  " 0  " M  •  vi  LIST OF PHOTOGRAPHS PHOTOGRAPH 1 and 2  " S t r i n g s of b r a s h i c e o f f  PAGE the n o r t h coast  of Gaspe P e n i n s u l a , March 20, 3 If- and 5  6 and 7 &  9  1952  11  Edge of b r a s h i c e o f f the mouth of M i r a m i c h i Bay, March 20, 1952  11  Landfast i c e , shore l e a d s , and open pack i c e along the n o r t h coast of P r i n c e Edward I s l a n d , March 20, 1952  12  Pack i c e of v a r y i n g s i z e d f l o e s  off  M i r a m i c h i Bay, March 20, I952  12  Sheets of i c e b r e a k i n g up o f f the New Brunswick coast south o f the Bale de C h a l e u r , March 20, 1952  13  A f i e l d of c l o s e pack i c e o f f the New Brunswick coast south of the Bale de Ghaleur, March 20, 1952  13  CHAPTER I INTRODUCTION THE PROBLEM The fundamental aim e f the p r e s e n t study  is  to  d i s c o v e r the d i s t r i b u t i o n o f i c e i n the breakup season and to trace  i t s behaviour throughout the months of March, A p r i l ,  and  May.  With t h i s d i s t r i b u t i o n and b e h a v i o u r e s t a b l i s h e d ,  is  proposed to determine the r e l a t i v e the p h y s i c a l f a c t o r s  influences  of the environment.  it  on the i c e o f  Finally, it  is i n -  tended that a p i c t u r e of average c o n d i t i o n s throughout the  ice  season should be p r e s e n t e d . Ice d i s t r i b u t i o n i n the G u l f of S t . Lawrence Is utmost importance to s h i p p i n g . Lakes-St.  A l l s h i p s e n t e r i n g the  Great  Lawrence system must pass through the g u l f .  whole system i s b l o c k e d to n a v i g a t i o n f o r n e a r l y f i v e of the y e a r due to i c e c o n d i t i o n s .  of  The months  The c o n d i t i o n s i n the  r i v e r can be r e a d i l y e v a l u a t e d by d i r e c t o b s e r v a t i o n from the l a n d , but the Gulf of S t . tion.  Lawrence p r e s e n t s a d i f f e r e n t  The a r e a of the g u l f  Is approximately  b i n e d areas of the f o u r maritime p r o v i n c e s . therefore,  situa-  equal t o the comIt  is  impossible,  t o a s c e r t a i n the i c e c o n d i t i o n s over such a l a r g e  a r e a from o b s e r v a t i o n s the i c e season the l a s t  taken along shore.  At the b e g i n n i n g of  v e s s e l s remaining i n the g u l f are  able  t o keep each o t h e r p o s t e d concerning the i c e c o n d i t i o n s i n t h e i r respective  vicinities.  On the other hand, because no  2 s h i p s are o p e r a t i n g i n the g u l f d u r i n g the w i n t e r other o b s e r v a t i o n a l arrangements must be made i n order t o determine when n a v i g a t i o n can s a f e l y  b e g i n d u r i n g the breakup season.  U n t i l 1940 t h i s estimate breakup depended c h i e f l y  of i c e c o n d i t i o n s d a r i n g the  on the r e p o r t s of the  i c e b r e a k e r s o p e r a t i n g i n the g u l f .  government  The i n f o r m a t i o n o b t a i n e d  was so s c a t t e r e d and i n c o m p l e t e , because there were so few v e s s e l s , t h a t i t proved inadequate f o r the purpose. quently,  w i t h the aim of d e c l a r i n g the g u l f open t o  Consenaviga-  t i o n as e a r l y as i c e c o n d i t i o n s i n a g i v e n a r e a would p e r m i t , an a e r i a l i c e  survey was inaugurated i n 1940 by the D e p a r t -  ment of T r a n s p o r t . since that time.  The survey has c o n t i n u e d every The r e p o r t s of t h i s  spring  survey p r o v i d e a w e a l t h  o f i n f o r m a t i o n which simply d i d not e x i s t  previously.  SOURCES OF INFORMATION The G u l f of S t . authoritative  Lawrence P i l o t  1  i s probably the most  source of p u b l i s h e d i n f o r m a t i o n on i c e c o n d i -  t i o n s i n the g u l f .  The treatment Is very b r i e f ,  does not d e a l s p e c i f i c a l l y  however, and  w i t h the breakup season.  Another  government p u b l i c a t i o n , A r c t i c Ice on Our E a s t e r n C o a s t ,  2  by  A . G. Huntsman, c o n t a i n s a short s e c t i o n concerning the G u l f of  S t . Lawrence, but the e v a l u a t i o n o f i c e c o n d i t i o n s i s u n -  ^-Department of Mines and Resources, G u l f of S t . rence P i l o t , T h i r d E d i t i o n . Ottawa, 1946.  Law-  ^Huntsman, "A. G . , A r c t i c Ice on Our E a s t e r n Coast, B u l l e t i n No. 13, B i o l o g i c a l Board of Gltnada. T o r o n t o , January, 1930.  sound and a b b r e v i a t e d .  The Ice A t l a s of the Northern Hemi-  sphere ,5 p u b l i s h e d by the U . S. Navy,  i n c l u d e s maps of  the  average l i m i t s of i c e f o r each month of the year i n the g u l f a r e a , however,  these are h i g h l y g e n e r a l i z e d .  Occasionally,  r e p o r t s o f i c e c o n d i t i o n s i n the g u l f appear i n the annual p u b l i c a t i o n of the I n t e r n a t i o n a l Ice Observation and l e e P a t r o l Service  i n the North A t l a n t i c Ocean,^ a l t h o u g h no  i n t e r p r e t a t i o n i s attempted.  Mr. J . G . G .  Kerry has w r i t t e n a  number of a r t i c l e s d e a l i n g w i t h i c e i n the g u l f and the  St.  Lawrence R i v e r (see b i b l i o g r a p h y , page 95).  esti-  mate i s i n c o m p l e t e , e s p e c i a l l y son.  In r e g a r d to the breakup s e a -  These few works c o n s t i t u t e  l i s h e d information i n respect  Again, his  the main sources of pub-  to i c e  conditions.  E x t r a c t i o n of i c e i n f o r m a t i o n from a l l these  sources  and from a d d i t i o n a l u n p u b l i s h e d and p u b l i s h e d m a t e r i a l was c a r r i e d out by the author d u r i n g the months from May to November, 1951, b u t i o n Survey.  i  n  c o n n e c t i o n w i t h the Canadian Ice  T h i s survey i s a p r o j e c t  Distri-  of the G e o g r a p h i c a l  B r a n c h , Department of Mines and T e c h n i c a l Surveys,  Ottawa,  and  the author was engaged i n t h i s work o f e x t r a c t i o n while i n the employ of the B r a n c h .  The main s o u r c e s , b e s i d e s the  aer-  S. Navy, Hydrographie O f f i c e , l e e A t l a s of the Northern Hemisphere, F i r s t E d i t i o n . Washington, 19457 k U. S. Treasury Department, Coast Guard, I n t e r n a t i o n a l l e e O b s e r v a t i o n and Ice P a t r o l S e r v i c e i n the North A t l a n t i c O l e a n . WashlngtonT^WT-1949.  4  lal  i c e survey r e p o r t s , 5 from which e x t r a c t s were taken were  the r e p o r t s of the I n t e r n a t i o n a l Ice P a t r o l S e r v i c e , ^ and the files  of the Canadian Hydrographic S e r v i c e .  7  A l l the  extracts  were c l a s s i f i e d a c c o r d i n g to a r e g i o n a l d i v i s i o n of the U n t i l r e c e n t l y the l a c k of d a t a s u f f i c i e n t l y  gulf.  detailed  t o support c o n c l u s i o n s has prevented the f u r t h e r a n c e of i n vestigation  i n t h i s f i e l d , but the appearance of the a e r i a l  i c e survey r e p o r t s p r o v i d e s an almost unprecedented opport u n i t y f o r a d e t a i l e d study of i c e c o n d i t i o n s i n the breakup season.  The present study i s based p r i m a r i l y on these d a t a .  Unfortunately, o f the g u l f  the f l i g h t  routes were c o n f i n e d t o t h a t p a r t  south of a l i n e from Heath P o i n t , A n t i c o s t i to  the Bay of I s l a n d s ,  Newfoundland.  As a r e s u l t ,  d i t i o n s i n the n o r t h e r n p o r t i o n of the g u l f ,  the Ice  i n c l u d i n g the  S t r a i t of B e l l e I s l e , are not c o n s i d e r e d i n d e t a i l .  Similarly,  i c e c o n d i t i o n s i n harbours and s m a l l e s t u a r i e s are not i n d e t a i l because the i c e r e p o r t s r e f e r c h i e f l y areas of the  con-  treated  t o the open  gulf.  The normal procedure of the a e r i a l observers was t o make s e v e r a l f l i g h t s  d u r i n g March to a s c e r t a i n the  quantity  ^Department of T r a n s p o r t , "Reports of A e r i a l Ice Surveys i n the Gulf o f S t . Lawrence, P i l e No. 6262-3, g V o l s . Ottawa, 1 9 4 0 - 1 9 5 2 . c °U. S. Treasury Department, op. c i t . 11  Department of Mines and Resources, Hydrographic S e r v i c e , "General Correspondence on Ice C o n d i t i o n s , P i l e No. 6 3 4 , V o l . 3. Ottawa, I 9 2 2 - I 9 5 I . Department of Mines and Resources, Hydrographic S e r v i c e , " Q u e s t i o n n a i r e , Re: l e e C o n d i t i o n s i n the Gulf of S t . Lawrence," F i l e No. 6 3 4 , V o l . 1 . Ottawa, 1 9 3 7 . 7  0  5 and extent o f i c e i n the g u l f before b e g i n n i n g d a i l y weather p e r m i t t i n g , toward the end o f the month. flights  were g e n e r a l l y  the g u l f , May.  flights,  These  daily  continued as l o n g as i c e remained i n  even i f t h i s n e c e s s i t a t e d  making s e v e r a l f l i g h t s  in  The r o u t e s f o l l o w e d were o f t e n v a r i e d from day to day i n  o r d e r t o g i v e a complete coverage  every few days o f  the  s e c t i o n of the g u l f w i t h i n the bounds of the survey. p o r t s were summarized and broadcast stations  The r e -  over the Maritime r a d i o  f o r the immediate warning o f v e s s e l s i n the  area.  To i n d i c a t e the type of i n f o r m a t i o n contained i n these r e p o r t s an excerpt  from the Canadian l e e D i s t r i b u t i o n Survey f i l e  p r e s e n t e d below. St.  George,  is  These d a t a r e f e r to r e g i o n 10 GD, Magdalen-  In the  file.  A p r i l 4 , 1942. "Prom 42.30 N . , 62.00 W., over steamer t r a c k to Gape Bay open water, from 23 m i l e s southwest of Gape Ray i c e extends s o u t h eastward and to the Cape Breton C o a s t . " A p r i l 9 , 1942. "Large f i e l d s i g h t e d , southern l i m i t s 46.30 N . , 61.00 W. A p r i l 23, 1942. "No Ice between S t . Paul I s l a n d and B i r d Rocks." A p r i l 24, 1942. "On a l i n e from Cape S t . George, Newfoundland, to Heath P o i n t two s m a l l growlers 48.40 N . , 59.40 W., 46.40 N . , 60.00 W. West coast of Newfoundland c l e a r t o v i c i n i t y of Bay o f I s l a n d s , s t r i n g s and patches f o r t y m i l e s o f f Heath P o i n t n o r t h and south of t h i s l i n e , then l a r g e f i e l d s t e n m i l e s o f f Heath P o i n t extending to Table Head, then southwestward t o 46.20 N . , 62.40 W., to 46.30 N . , 63.30 W . , to 46.55 N . , 63.15 W., to South P o i n t . " 8  Department of Mines and T e c h n i c a l Surveys, G e o g r a p h i c a l Branch, "Canadian Ice D i s t r i b u t i o n Survey Ottawa, 1951.  Pile,"  6 PROCEDURES Such d e t a i l e d i n f o r m a t i o n p r o v i d e d the b a s i s f o r a s e r i e s of maps d e p i c t i n g the i c e c o n d i t i o n s at ten-day vals.  inter-  An i n t e r v a l of t h i s l e n g t h was necessary because of  the blanks i n the r e c o r d which o c c u r r e d as a r e s u l t of adverse f l y i n g c o n d i t i o n s or incomplete coverage o f the a r e a . The dates chosen were March 15, A p r i l 25, May 1,  and May 5.  March 25, A p r i l 5,  April.15,  The mapping at f i v e - d a y  inter-  v a l s a f t e r A p r i l 25 was made p o s s i b l e by the more a c c u r a t e p o r t s l a t e r i n the season.  re-  Greater accuracy at t h i s time  might be expected because the i c e areas are so reduced that  it  i s easy to c a r r y out complete o b s e r v a t i o n s . The maps were designed to show the type of a t these dates w i t h the use of s u i t a b l e symbols. i n t e r p o l a t i o n was necessary  ice-cover Considerable  i n the c o n s t r u c t i o n of these maps,  i n order t h a t a complete p i c t u r e of the probable i c e c o n d i t i o n s on each date might be a c h i e v e d . necessity,  In s p i t e - o f  the maps are c o n s i d e r e d as reasonably  this  accurate.  Supplementary notes p o i n t i n g out the changes i n i c e c o n d i t i o n s which o c c u r r e d between the dates were w r i t t e n to accompany the maps.  The t o t a l number of maps produced was  sixty-two.  Some years r e q u i r e d more maps than o t h e r s , depending on the amount of i n f o r m a t i o n a v a i l a b l e and the date of f i n a l c l e a r i n g of the g u l f . facilitate  These maps were too numerous, however,  ready comparison of separate years w i t h a view  toward determining the p a t t e r n s and r a t e s of breakup.  to  7 A procedure was e s t a b l i s h e d to reduce the m a t e r i a l t o more manageable p r o p o r t i o n s without l o s i n g v a l u a b l e  detail.  Upon i n s p e c t i o n of the s e r i e s of maps f o r each year and examin a t i o n of the supplementary notes, scribed i n detail.9  i c e c o n d i t i o n s were de-  At the same t i m e , a new map was drawn f o r  each season i n c o r p o r a t i n g the main f e a t u r e s  of the b a s i c maps.  T h i s map showed the l i m i t s of the main i c e areas at each d a t e . While i t gave no i n d i c a t i o n of the percentage cover,  or type of  ice-  i t d e p i c t e d more g r a p h i c a l l y the ehanges i n p o s i t i o n  o f the i c e f i e l d s as the season p r o g r e s s e d .  Copies of these  maps may be found i n the Appendix. Ice c o n d i t i o n s d u r i n g the breakup i n these t h i r t e e n seasons were r e l a t e d to the determining p h y s i c a l f a c t o r s the environment.  of  The c o r r e l a t i o n w i t h the m e t e o r o l o g i c a l  f a c t o r s was e f f e c t e d  through the use of s t a t i s t i c s  published  by the M e t e o r o l o g i c a l D i v i s i o n , Department of T r a n s p o r t . Mainly government p u b l i c a t i o n s were c o n s u l t e d i n the examin a t i o n of the other  factors.  The d e s c r i p t i o n of average w i n t e r c o n d i t i o n s was based chiefly  on the data e x t r a c t e d from the Canadian Hydrographic  Service f i l e s  1 0  and from the r e p o r t s of the I n t e r n a t i o n a l  Ice  ^These d e s c r i p t i o n s are i n c l u d e d i n the complete r e p o r t on i c e d i s t r i b u t i o n i n the Gulf of St. Lawrence d u r i n g the breakup season which was submitted to the Geographical B r a n c h , Department of Mines and T e c h n i c a l Surveys, Ottawa, i n September, 1952. •^Department of Mines and Resources, op.  cit.  Patrol S e r v i c e .  1 1  The f i l e s  c o n t a i n the r e p l i e s to a q u e s t i o n -  n a i r e which was sent to s k i p p e r s of v e s s e l s ,  light-keepers,  and other persons who might he expected to possess of ice conditions.  The r e p o r t s of the I n t e r n a t i o n a l  Patrol Service occasionally St.  Lawrence.  knowledge  contain references  Ice  to the Gulf of  T h i s i n f o r m a t i o n , t o g e t h e r w i t h t h a t from o t h e r  s o u r c e s , was s i f t e d and c r o s s - c h e c k e d In order to achieve an • e v a l u a t i o n of w i n t e r i c e c o n d i t i o n s which was reasonably accurate.  The accuracy of the d e s c r i p t i o n of s p r i n g i c e c o n -  d i t i o n s was b e t t e r  s t i l l because i t was based on the a e r i a l  survey r e p o r t s as w e l l as on the Hydrographic S e r v i c e  files.  TERMINOLOGY A number of terms appear throughout the study which require d e f i n i t i o n s .  S e v e r a l of these terms have a s p e c i a l  meaning i n t h i s context which may not c o i n c i d e w i t h t h e i r meaning elsewhere, types.  I n c l u d e d i n the f i r s t group are the terms  "breakup," ice  w h i l e others are accepted terms f o r  "ice season,"  conditions."  " G u l f of S t . whole g u l f  "light ice  While " g u l f "  "gulf,"  c o n d i t i o n s , " and "heavy  i s an a b b r e v i a t e d form f o r  Lawrence," i t g e n e r a l l y  i n t h i s study,  ice  does not apply to  the  but r a t h e r to t h a t p a r t south of a  l i n e from Heath P o i n t , A n t i c o s t i to the Bay of  Islands,  Newfoundland, f o r which a r e a d e t a i l e d i c e Information i s available.  When i t a p p l i e s to the whole Gulf of S t .  the context makes t h a t apparent.  1 1  U.  Lawrence  The word "breakup" i s used  S. Treasury Department, op.  cit.  i n the f o l l o w i n g study i n a wide sense.  Not only the  actual  b r e a k i n g up of i c e sheets i s i m p l i e d , but a l s o the c l e a r i n g of i c e from the g u l f .  "Ice  season" i s understood as the p e r i o d  from November to May when i c e i s p r e s e n t  i n the g u l f .  term " l i g h t  i n d i c a t i n g that  ice  ice conditions" i s r e l a t i v e ,  i n the g u l f  Is l e s s  extensive  mostly under two f e e t t h i c k . conditions" indicates t h i c k e r than two  Conversely,  the term "heavy  the i c e i s r e l a t i v e l y  of i c e terms which f o l l o w s  ice terminology.  Brash i c e  than i n other areas and  -  ice  extensive  and  i s adapted w i t h  from a U. S. Hydrographic O f f i c e  the photographs  the  feet.  The l i s t modifications  that  The  1 2  p u b l i c a t i o n on  Some of the i c e types are i l l u s t r a t e d by  on pages n ,  12,  and  13.  Small i c e fragments l e s s than s i x f e e t the wreckage of other forms of i c e .  across;  C l o s e pack  Pack composed of f l o e s mostly i n c o n t a c t . It i s g e n e r a l l y unnavigable to o r d i n a r y s h i p s .  Drift  Loose, very open pack, where water predominates over i c e . The f l o e s are u s u a l l y s m a l l e r than i n c l o s e o r open pack w i t h much r o t t e n i c e , and v e s s e l s can u s u a l l y pass through i t without a l t e r i n g course or speed.  ice  Fast ice or l a n d f a s t Tee  Sea i c e which remains f a s t i n the p o s i t i o n of growth, found along c o a s t s where I t Is a t t a c h e d to the shore, o r over shoals where I t may be h e l d i n p o s i t i o n by i s l a n d s o r grounded Icebergs.  Field  The l a r g e s t of i c e a r e a s , miles across.  Floe  A p i e c e of sea i c e o t h e r than f a s t or s m a l l .  g r e a t e r than ice,  five large  *=U. S. Navy, Hydrographic O f f i c e , "A F u n c t i o n a l G l o s s a r y of Ice Terminology," Study No. 103, P r o v i s i o n a l , May, 1946. A  10 Growler  A s m a l l p i e c e of g l a c i e r Ice, u s u a l l y g r e e n i s h i n c o l o u r and b a r e l y showing above the water.  Heavy Ice  - Any t h i c k f l a t  Lead  - A passage through pack i c e . Leads may form e i t h e r by the widening of a crack or by a g e n e r a l l o o s e n i n g of the f l o e s . A shore-lead i s a s t r e t c h of n a v i g a b l e open water formed when pack i c e moves away from the f a s t i c e under the i n f l u e n c e of wind o r t i d e .  Light  Ice  -  ice.  Ice of medium t h i c k n e s s ,  l e s s than two f e e t .  Open pack  - Pack composed of f l o e s which f o r the most p a r t do not t o u c h . B e l t s are u s u a l l y narrow w i t h many l e a d s and p o o l s . E a s i l y n a v i g a b l e but speed i s slow and changes of course c o n t i n u a l l y necessary.  Pack i c e  - Sea i c e which has d r i f t e d from i t s position.  Pool  - Any e n c l o s e d sea-water a lead.  Sheet i c e  - A l a r g e p i e c e of f l o e unbroken.  original  i n the pack,  other than  i c e that d r i f t s to  sea  ORGANIZATION The p h y s i c a l geography  of the G u l f of S t .  i n c l u d i n g the s u b a e r i a l and submarine morphology,  Lawrence, the  movements and p h y s i c a l c h a r a c t e r i s t i c s of the water, elimate,  i s examined i n g e n e r a l d e t a i l .  and the  Average w i n t e r  c o n d i t i o n s are then d i s c u s s e d by months.  With t h i s  ice  back-  ground, the a c t u a l observed i c e d i s t r i b u t i o n d u r i n g the b r e a k up seasons of ISkO to 1952,  inclusive,  i s presented,  together  w i t h an i n d i c a t i o n of the a i r temperatures which p r e v a i l e d throughout the i c e season.  Maps of i c e l i m i t s at  specified  d a t e s i n A p r i l and temperature graphs accompany t h i s p r e s e n t a t i o n of d a t a .  Based on t h i s d a t a , the p a t t e r n s and r a t e s  Photos. 1 and 2. S t r i n g s of b r a s h i c e o f f the n o r t h coast of Gaspe P e n i n s u l a , March 20, 1952 (courtesy of Miss I . M. Dunbar).  •  Photo. Edge of b r a s h i c e o f f the mouth o f M i r a m i c h i Bay, March 20, 1952 (courtesy of Miss I . M. Dunbar).  Photos. K and 5. Landfast i c e , shore l e a d s , and open pack Ice along the n o r t h coast of P r i n c e Edward I s l a n d , March 20, 1952 (courtesy of Miss I . M. Dunbar and Miss M. R. Montgomery).  Photos. 6 and 7. Pack i c e of v a r y i n g s i z e d f l o e s o f f M i r a m i o h i Bay, March 20, I952 (courtesy of Miss I . M. Dunbar and Miss M. R. Montgomery).  Photo. g . Sheets of i c e b r e a k i n g up o f f the New Brunswick coast south of the B a i e de Chaleur, March 20, 1952 (courtesy of Miss I . M. Dunbar).  Photo. 9. A f i e l d o f c l o s e pack i c e o f f the New Brunswick coast south of the Baie de C h a l e u r , March 20, I952 (courtesy of Miss I . M. Dunbar).  o f breakup are i s o l a t e d and c l a s s i f i e d . factors  Then the  physical  d i s c u s s e d at the beginning are re-examined w i t h the  aim of r e l a t i n g them to the d i s t r i b u t i o n and b e h a v i o u r o f i c e and determining t h e i r i n f l u e n c e .  F i n a l l y , the  the  general  c o n c l u s i o n s are s t a t e d and the average i c e c o n d i t i o n s d u r i n g March and A p r i l are d e s c r i b e d .  This description  complements  the statement of w i n t e r i c e c o n d i t i o n s , thereby g i v i n g e n t i r e p i c t u r e of the i c e season.  the  The map f o l l o w i n g page Ik-  shows the l o c a t i o n s o f p l a c e s mentioned i n the  text.  51  49<  NEWFOUNDLAND G U L F  OF  LAWRENCE  ST.  C A P E  A N G U I L L E  c % /SH I P P I G AN  C A P E  R A Y L  M A G D A L E N  ST  P A U L  I  CAPE  *1 0 R T H  Ml Q U E LON  NEW  \ . \ f  A T  ^ a  PRINCE EDWARD ISLAND  o  B R U N S W I C K SCATA Rl I. V  ,—-'LOUISBUPG  MAP  GULF  OF ST.  PLACE  LAWRENCE  NAMES  SCALE IN MILES 20  Map 1 ( t o f o l l o w page  1H-)  62'  60  1  40  45<  CHAPTER I I PHYSICAL GEOGRAPHY SUB AERIAL AND SUBMARINE MORPHOLOGY The Gulf of S t .  Lawrence l i e s  two p h y s i o g r a p h i c p r o v i n c e s .  on the boundary  On the n o r t h the g u l f  between  i s bounded  by the Precambrian r o c k s of the Canadian S h i e l d and on the west, s o u t h , and east c h i e f l y f o l d e d and f a u l t e d ,  by the P a l a e o z o i c r o c k s ,  greatly  of the Appalachian Highlands P r o v i n c e .  Two main ranges of the Appalachian system are t r a c e a b l e region.  i n the  These are the Shickshock Range of Gaspe p e n i n s u l a and  the h i g h l a n d s of Nova S c o t i a , which continue northeastward the Long Range of Newfoundland.  The f o l d mountains of Gaspe  curve southeastward toward the Nova S c o t i a range before appearing below the waters  of the g u l f ,  range maintains i t s northeast-southwest c l o s i n g the  while the  dis-  southern  t r e n d , thereby  en-  gulf.  The g u l f Cape Gaspe t o S t .  Itself  i s much deeper n o r t h of a l i n e from  Paul I s l a n d than south of i t  f o l l o w i n g page 15).  ( see map  A submarine canyon, whose bottom  range from 150 to JQQ fathoms below the s u r f a c e , the. g u l f from the estuary  of the S t .  Gaspe, n o r t h of the Magdalen I s l a n d s ,  depths  traverses  Lawrence R i v e r past through Cabot  Strait  and southeastward to the edge of the c o n t i n e n t a l s h e l f  America.  as  where  !3Atwood, W. W., The P h y s i o g r a p h i c P r o v i n c e s of North Boston: Ginn and Company, 1940, p . 67. ~  it  separates  Bank St.  P i e r r e from Banquereau Bank.  of t h i s canyon extend up the northeast the S t r a i t  Branches  arm of the g u l f  toward  of B e l l e I s l e and northwestward between A n t i c o s t l  I s l a n d and the Quebec mainland.  These s t e e p - w a l l e d  canyons  are 40 to 100 m i l e s broad and occupy much of the n o r t h e r n and eastern sections  of the g u l f .  On the other hand, the  of the roughly c i r c u l a r a r e a south of the t r a n s v e r s e l i e s l e s s than f i f t y likely  fathoms below the s u r f a c e . ^  floor canyon  Ice Is more  1  to form i n shallow areas because there i s not so g r e a t  a body of water which must be c o o l e d before  f r e e z i n g can take  place. Of the three Atlantic,  straits  Cabot S t r a i t  connecting the g u l f w i t h the open  i s the w i d e s t .  It  i s apparent t h a t a  g r e a t e r volume of Ice w i l l gain e x i t from the g u l f this  s t r a i t d u r i n g the breakup season than through e i t h e r  Strait  of B e l l e I s l e o r the S t r a i t  Strait  of Canso i s e s p e c i a l l y  gulf  through  of Ganso.  Because  the  the  narrow, the southern p a r t of  the  i s more confined than the c e n t r a l s e c t i o n and i c e  movement i s r e s t r i c t e d .  S i m i l a r l y , the northeast  confined,  of B e l l e I s l e p r o v i d e s a wider l i n k  but the S t r a i t  w i t h the open ocean.  arm i s  A n t l c o s t i I s l a n d , the Magdalen  Islands,  and P r i n c e Edward I s l a n d tend to h i n d e r the f r e e movement' of i c e over the surface  of the  gulf.  The s h o r e l i n e s of the Gulf of S t . c l a s s i f i e d as primary or y o u t h f u l ,  ^Smith, F.G.G. Year Book 194?. Ottawa,  Lawrence area are  t h e i r configuration being  "Hydrographical F e a t u r e s , " 1947, p. 7.  Canada  due mainly t o non-marine e r o s i v e f o r c e s . ! 5 formed c h i e f l y  These coasts are  hy the drowning of f o l d e d , f a u l t e d ,  a t e d topography  and, as a r e s u l t ,  they  are d i v e r s e  The s h o r e l i n e s are c h a r a c t e r i z e d throughout by  and g l a c i i n form.  indentations  which conform e s s e n t i a l l y  w i t h the alignment and the  o f the r o c k s t r u c t u r e .  It  1 0  i s notable  that the western and  southern s h o r e l i n e s of the g u l f have numerous b r o a d , embayments the g u l f  i n contrast  nature  shallow  to the Precambrian s h o r e l i n e , bounding  on the n o r t h , where the bays are small and the  I s deep o f f s h o r e .  water  The b r o a d , shallow bays p r o v i d e great  areas  o f p r o t e c t e d water surface where i c e forms more r e a d i l y and where the breakup i s slower than i n unprotected r e g i o n s . detainment  of the i c e d u r i n g the breakup season i s  u l a r l y noticeable  i n the Baie de Chaleur because  The  partic-  the mouth of  the bay i s narrowed by Miscou and Shippigan i s l a n d s .  On the  o t h e r hand, the smooth n o r t h coast o f Gaspe does not h i n d e r the f r e e d r i f t  of i c e i n t o the g u l f d u r i n g the breakup. WATER MOVEMENTS AND PROPERTIES  W i t h i n the p h y s i o g r a p h i c framework of the g u l f water movements and p r o p e r t i e s g r e a t l y of f l o a t i n g the t i d e s ,  ice.  Among the f a c t o r s  t i d a l c u r r e n t s , and ocean  affect  the  behaviour  which cause movement  are  currents.  5shepard, F r a n c i s P . , Submarine Geology. Harper and B r o t h e r s , 1946, p . JW. 1  the  New York:  •^Johnson, Douglas W., The New England-Acadian Shoreline. New York: John Wiley and Sons, 1925, p . 20-23.  Tides and T i d a l C u r r e n t s T i d e s are wave motions which i n v o l v e no a p p r e c i a b l e h o r i z o n t a l movement of water, but r a t h e r , a v e r t i c a l r a i s i n g and l o w e r i n g o f the water i n r e l a t i o n to a datum p l a n e .  They  are generated p r i n c i p a l l y i n the open oceans of the world and not i n the c o n f i n e d c o a s t a l b a s i n s where they are most noticeable. ? 1  The t i d a l u n d u l a t i o n e n t e r s the g u l f mainly  through Cabot S t r a i t and progresses  in a  counter-clockwise  d i r e c t i o n around a c e n t r a l p o i n t west of the Magdalen Islands. ^ 1  The d i s t u r b a n c e of the water surface by t i d e  d e r s the formation of l a r g e  hin-  sheets of i c e and a i d s i n the  b r e a k i n g up of sheets which have become e s t a b l i s h e d . s h a t t e r i n g a c t i o n i s more e f f e c t i v e where the t i d a l  This ranges  are high. The range of t i d e i n the open ocean i s seldom more than 1 metre, but t h i s i s a m p l i f i e d a l o n g shallow  coastlines,  i n many c a s e s , by t i d a l components o t h e r than those which are gravitational gulf,  in nature. 9  On the map of t i d a l ranges i n the  1  f o l l o w i n g page 19,  ranges of s p r i n g t i d e s .  the l i n e s j o i n p l a c e s h a v i n g equal w  These v a l u e s ,  expressed i n metres,  S t e w a r t , John Q . , Coasts, Waves and Weather. B o s t o n : Ginn and Company, 1945, P. 207. 1 7  K r i e g s m a r l n e , Ubootshandbuch d e r Ostkdste B e r l i n , 1942, p . l b b .  (Atlas).  ^Stewart,  op. c i t . ,  p.  Kanadas  192.  When the g r a v i t a t i o n a l p u l l s of the sun and moon are combined along the same l i n e , as occurs at new and f u l l moon, the t i d e s produced are both h i g h e r and lower than at other times. These are termed s p r i n g t i d e s . 20  are computed from t i d e t a b l e s which do not i n c l u d e the caused by m e t e o r o l o g i c a l  conditions.  employed were taken a t c o a s t a l  Because the  stations,  readings  adjustments  e s s a r i l y made i n order t h a t average v a l u e s f o r the areas might be d e r i v e d .  As a r e s u l t ,  s t a t i o n s may not appear t o f i t i n the g u l f  are not g r e a t ,  the estuary  of t h e - S t .  S t r a i t than elsewhere. most pronounced. range i s 1.5  offshore  f o r some  coastal Ranges  Lawrence R i v e r and i n Northumberland In these areas t i d a l s h a t t e r i n g  Prom the mouth of the estuary  metres the range i n c r e a s e s  west of the Magdalen I s l a n d s ,  where  is  the  upstream t o more than  In the v i c i n i t y  of Gape  the range i s 1.5  than 0.5 metres are c h a r a c t e r i s t i c  on i c e  nec-  as a r u l e , but are h i g h e r toward  Tormentlne i n Northumberland S t r a i t  tides  were  the p a t t e r n i n d i c a t e d .  3 metres above Pointe des Monts.  Ranges l e s s  figures  extremes  consequently,  metres.  of the  area  the e f f e c t  of  sheets i n t h i s a r e a i s minimized.  When t i d a l u n d u l a t i o n s p r o g r e s s through shallow  water  an a c t u a l h o r i z o n t a l movement o f the water takes p l a c e .  Such  h o r i z o n t a l movements are termed t i d a l c u r r e n t s . seldom c o i n c i d e w i t h the time of h i g h water, r e v e r s e d i n rhythm w i t h the t i d e s . generally  less  o f Ganso the t i d a l c u r r e n t s are, d e c i d e d l y  approximately  1 to 1.5  Strait  stronger.  In entrances  Bale Verte and t h e i r strengths  knots.  The S t r a i t  are  are  but i n the  the c u r r e n t s flow from both  meeting i n the middle o f f  currents  although they  Their v e l o c i t i e s  than 1 knot i n open a r e a s ,  Northumberland S t r a i t  These  are  of B e l l e I s l e has  c u r r e n t s which are t i d a l In c h a r a c t e r , but i n a d d i t i o n ,  there  i s a dominant flow i n one d i r e c t i o n o r the other f o r p e r i o d s  70°  66"  62°  58°  54°  of a week o r m o r e . between 0.5 gulf  d l  The v e l o c i t i e s  and over 2 k n o t s .  i n the s t r a i t  range  In most other s e c t i o n s  the t i d a l c u r r e n t s are weak and i l l - d e f i n e d .  effective  In checking o r i n c r e a s i n g the v e l o c i t y  of  the  Winds are of  tidal  currents. Ocean C u r r e n t s Superimposed upon the system of t i d e s and t i d a l c u r r e n t s i s a system of constant respect  the Gulf of S t .  clockwise  ocean c u r r e n t s .  In  this  Lawrence i s c h a r a c t e r i z e d by a c o u n t e r -  c i r c u l a t i o n (see map f o l l o w i n g page  21).  Water from the ocean pours i n t o the g u l f  around Gape  Ray and, due to the i n f l u e n c e  of the e a r t h ' s  rotation,  curves to the r i g h t and flows  northeastward a l o n g the west  coast of Newfoundland as f a r as P o i n t R i c h e . current, a belt a velocity  near shore ten to f i f t e e n  of a l i t t l e  t o the Bay of I s l a n d s appreciable, about 1 k n o t ,  l e s s than 1 k n o t .  Prom Gape S t .  the movement of the water i s  effect  w i t h i n the g u l f .  2 2  hardly at  The c u r r e n t  of keeping the southwest and west of i c e l a t e r than o t h e r  Much of the water i n t h i s c u r r e n t  stream and spreads out northwestward,  areas departs  heading  across  A 1 t h o u g h the cause of t h i s dominant flow i s not known, i t i s thought to be c h i e f l y m e t e o r o l o g i c a l . 21  fully  D e p a r t m e n t of Mines and Resources, G u l f of St. Lawrence P i l o t , T h i r d E d i t i o n . Ottawa, 1946, p . L V I . 22  has  George  i s constant  s t r o n g e r near l a n d than o f f s h o r e .  c o a s t s of Newfoundland f r e e  from the  At Gape Ray the  miles i n width,  but northward of t h i s p o i n t i t  has the b e n e f i c i a l  it  the g u l f i n a weak movement to A n t i c o s t l I s l a n d .  In f a c t ,  the  preponderance of flow i n t h i s whole n o r t h e r n a r e a to a c o n s i d e r a b l e depth i s toward the S t . Lawrence e s t u a r y ,  although the  v e l o c i t i e s are low and the d i r e c t i o n of movement i s r e a d i l y affected  by the wind.  Nevertheless,  a great q u a n t i t y of  ice  i s c a r r i e d southward and westward from the S t r a i t of B e l l e Isle area.  The c u r r e n t s i n the s t r a i t i t s e l f are e n t i r e l y  t i d a l i n character. At the mouth of the S t . Lawrence R i v e r water from the n o r t h e r n p a r t of the g u l f generate  combines w i t h t h a t from the r i v e r to  the Gaspe C u r r e n t .  The c u r r e n t begins at Gap Chat  and, d e f l e c t e d t o the r i g h t , i t hugs the Gaspe coast as flows  eastward.  Although I t  it  i s constant at an average v e l o c i -  t y of 2 k n o t s , the t i d e s do cause v a r i a t i o n s i n speed, i n s p i t e of the f a c t the flow. and i t  that  they cannot r e v e r s e or completely  check  The approximate width of the c u r r e n t i s twelve m i l e s  seldom extends f u r t h e r than f o u r t e e n m i l e s o f f s h o r e . 23  A l a r g e amount of i c e formed i n the S t .  Lawrence r i v e r and  estuary i s d e p o s i t e d i n the g u l f by the Gaspe C u r r e n t . L e a v i n g Gape Gaspe the c u r r e n t flows but the v e l o c i t y area, f i l l i n g  i s much reduced and i t  southeastward,  spreads over a wide  up the c e n t r a l p a r t of the g u l f .  The predomi-  nant d r i f t i n t h i s c e n t r a l s e c t i o n Is eastward a c r o s s t o the Magdalen I s l a n d s and Cape B r e t o n .  The v e l o c i t y ,  however,  only 0 . 5 t o 1 knot and there Is no constant c u r r e n t  2  5 l b l d . , p. LIX.  is  22 discernible. ^"  In the southern p a r t  2  In Northumberland S t r a i t , The l a c k of constant  of the g u l f ,  the c u r r e n t s are t i d a l i n  currents i n t h i s  character.  s e c t i o n of the  p e r m i t s the accumulation and s t a g n a t i o n some  particularly  gulf  of i c e i n t h i s a r e a on  occasions. The Gaspe Current i s rejuvenated  by the c o n s t r i c t i o n o f Cabot S t r a i t . comparable i n constancy the Cape Breton coast  in its  continuation  An 18-mile-wide  w i t h the Gaspe Current flows  a few m i l e s o f f  by a dominant flow of water  Cape N o r t h .  current along  Fed c h i e f l y  southeastward from the n o r t h e r n  end of the Magdalen I s l a n d s t o Gape N o r t h , i t s v e l o c i t y times reaches 2 k n o t s . 5 2  The Cape Breton c u r r e n t extends  a weak flow along the c o a s t , T h i s c u r r e n t i s of g r e a t the g u l f ,  especially  often as f a r as S c a t a r l  In a d d i t i o n , t h e i r e f f e c t  from the g u l f  i s minor beeause  g u l f discharges  from  d u r i n g the breakup.  Lawrence/ are too s m a l l t o g i v e r i s e to  currents.  as  Island.  Importance I n t r a n s p o r t i n g i c e  Most of the r i v e r s which flow i n t o the g u l f , the S t .  at  except  significant  on the c l e a r i n g of  the b u l k of the Ice  through Cabot S t r a i t before  the  Ice  In the  rivers  break up. Physical  Properties  As p a r t of the A t l a n t i c Oeean, the Gulf Lawrence Is f i l l e d w i t h s a l t water s l i g h t l y  of  St.  modified i n  ^^Department of the Naval S e r v i c e , The Currents In the Gulf of S t . Lawrence. Ottawa, 1913, p. 11. ^Department  of Mines and Resources,  op. c i t . ,  p. LVI.  c e r t a i n s e c t i o n s by the a d d i t i o n of f r e s h water. g a t i o n s have determined that gulf,  Investi-  i n the southwestern h a l f of  south of a l i n e from G-aspe to S t .  the  Paul I s l a n d , the  water  i s warmer and of lower d e n s i t y than i n the n o r t h e a s t e r n h a l f . The d e n s i t y  i n . t h i s n o r t h e a s t e r n s e c t i o n i s much the same as  i n the open A t l a n t i c .  The G-aspe and Gape Breton c u r r e n t s are  comparable i n having d e c i d e d l y lower d e n s i t i e s o u t s i d e the  than the  waters  currents. ^ 2  The temperature c h a r a c t e r i s t i c s are not w e l l known, but i t  i s e s t a b l i s h e d that a c o l d l a y e r of water l y i n g at a  depth of about 50 fathoms  i s constantly  the f r e e z i n g p o i n t and t h a t above and below.  it  at a temperature near  separates warmer l a y e r s b o t h  The water above 3  Q  fathoms i s i n f l u e n c e d by  the temperature of the a i r i n contact w i t h i t . 7  Regarding  2  s u r f a c e temperatures, whieh have the g r e a t e s t b e a r i n g on the . ice formation process,  It  is definite  t h a t i n most  sections  o f the g u l f the surface water temperatures do f a l l below the f r e e z i n g p o i n t of s a l t water.  Ice f o r m a t i o n Is  especially  pronounced around the Magdalen I s l a n d s and i n the bays and s t r a i t s , umberland S t r a i t .  shallow  i n c l u d i n g the Bale de Chaleur and N o r t h Throughout the open g u l f ,  ^Department of the Naval S e r v i c e ,  however,  op. c i t . ,  ice  p.  is  36.  ?Department of the Naval S e r v i c e , Temperatures and D e n s i t i e s of the Waters of E a s t e r n Canada. Ottawa, 1922, P- 7. 2  not formed on a l a r g e the g r e a t e r  scale  due to a g i t a t i o n of the water and  depths. ^ 2  CLIMATE The c l i m a t e of the G u l f of S t .  Lawrence r e g i o n i s not  so marine i n c h a r a c t e r as might be expected, location.  L y i n g i n the b e l t  mainly under the i n f l u e n c e sea.  of Westerly Winds, the area  its is  of a i r which moves from l a n d to  The p a t h of the most frequent  directly  considering  c y c l o n i c storms passes  a c r o s s the c e n t r a l p a r t of the g u l f .  This c o n t i -  n e n t a l a i r i s modified to a c e r t a i n e x t e n t , r e s u l t i n g i n more moderate c o n d i t i o n s than those which are experienced i n l a n d . Because the m e t e o r o l o g i c a l necessary gulf.  to g e n e r a l i z e  records are taken on l a n d i t  concerning the c o n d i t i o n s over  The temperature w i l l be more moderate over the  and the p r e c i p i t a t i o n l o w e r , as a r u l e . greater velocity  i n view of the f a c t  that  Winds may  i s .the  water  achieve  obstructions  are  lacking.  S a l t water does not behave i n the same manner as f r e s h water when i t i s c o o l e d . The maximum d e n s i t y of f r e s h water i s at k-°0. When a body of water has been c o o l e d to t h i s temperature, from top to bottom, f u r t h e r c o o l i n g at the s u r f a c e w i l l not perpetuate the c o n v e c t i o n c u r r e n t s , but w i l l l e a d to more r a p i d c o o l i n g and eventual i c e f o r m a t i o n at 0 G . S a l t water reaches i t s c o n d i t i o n of g r e a t e s t d e n s i t y at - 2 ° C , which i s s l i g h t l y below i t s f r e e z i n g p o i n t ( - l . g ° C ) . As a r e s u l t , c o n v e c t i o n c u r r e n t s are generated that keep r e p l a c i n g the surface water u n t i l , and i f c o n d i t i o n s p e r m i t , even a f t e r i t reaches i t s f r e e z i n g p o i n t . The f r e e z i n g o f s a l t water i s thus r e t a r d e d -by i t s p h y s i c a l p r o p e r t i e s . In a d d i t i o n , the d i s t u r b a n c e and mixing of the water by winds, t i d e s , and c u r r e n t s p l a y s an important r o l e i n the i c e formation p r o c e s s . G  25 Temperature During the w i n t e r the isotherms tend t o run n o r t h e a s t southwest  a c r o s s the g u l f  (see map f o l l o w i n g page 2 5 ) .  The  Cabot S t r a i t r e g i o n experiences temperatures about t e n degrees F a h r e n h e i t h i g h e r than those o f the Quebec n o r t h shore because of the moderating i n f l u e n c e of the open A t l a n t i c . difference  i n temperature i s r e f l e c t e d i n the dates of c l o s i n g  o f n a v i g a t i o n i n harbours throughout the g u l f i n g page 3 2 ) . g u l f freeze  This  (see map f o l l o w -  The harbours i n the southeastern p a r t of  the  l a t e r than those i n the northwestern p a r t .  The accompanying t a b l e , page 26, I n d i c a t e s  that  average monthly temperatures throughout the g u l f drop below the f r e e z i n g p o i n t i n December and remain there u n t i l It  April.  i s apparent t h a t the a i r temperature i s low enough to g i v e  r i s e to i c e formation even on s a l t water I f other combine to make i t p o s s i b l e . form,  In the event t h a t  factors  i c e does not  temperature c o n d i t i o n s are such as to p r e s e r v e i c e which  may have formed elsewhere  and d r i f t e d i n t o the g u l f .  Temper-  a t u r e s are s t i l l near f r e e z i n g d u r i n g A p r i l when the breakup i s w e l l advanced. The v a r i a b i l i t y of i c e season temperatures i s h i g h . I n a g i v e n year the d i f f e r e n c e  from average of the mean  monthly temperature might be f i v e stations  i n the g u l f a r e a .  or ten degrees at many  Frequently, several  consecutive  months i n one season experience temperatures somewhat h i g h e r o r lower than average.  The s e v e r i t y  of i c e c o n d i t i o n s i s  l a r g e l y dependent on these year to y e a r f l u c t u a t i o n s of  I S O T H E R M S OF M E A N MONTHLYc D E C R E E S  TEMPERATURE  F A H R E N H E I T  CCLIMATIC M A P  Map  5  S U M M A R I E S ,  S  ( t o f o l l o w page  25).  19 4 8)  TABLE I MONTHLY AVERAGES OF DAILY MEAN TEMPERATURE Meteorological Station* Beraimis Father P o i n t Clarke C i t y Natashquan H a r r i n g t o n Harbour Cap Chat Cap Magdalen E l l i s Bay A n t i c o s t i (S.W.Pt.) Gaspe" Port Daniel Bathurst Chatham Rezton Summers!de Charlottetown Alliston Antigonish Chetieamp Baddeck Sydney Grindstone I s l a n d S t . Paul Island Burgeo Channel S t . Georges Corner Brook i  November  December  January  February  27 29 26  14 17 11 13 13 19 18 18 20 17 19 18 19 30 24 23 26 27 29 27 29 23 27 29 28 28 23  2  8 11 6 6  2  2  28 32 31 30 30 30 31 32 33 36 36 38 38 5  2  38 38 36 37 33 36 33 34  9  2 6 8 13 11 13 12 10 12 10 12 13 18 18 20 20 22 27 29 19 27 23 22 21 18  9  13 14 12 12 11 12 11 12 14 18 17 20 18 20 20 20 16 18 21 21 16 18  F o r l o c a t i o n s o f m e t e o r o l o g i c a l s t a t i o n s see map f o l l o w i n g page 40.  March 20 22 18 17 20 22 21 20 21 22 27 24 23 23 26 26 28 28 27 26 27 23 £ 26 23 24 23 2  April 33 34 31 30 30 33 32 31 31 33 34 36 37 33 37 36 37 37 36 37 36 32 32 33 33 33 33  27 temperature.  Consequently,  In the examination of i c e c o n -  d i t i o n s during a thirteen-year p e r i o d , i t  i s desirable  to  r e l a t e the r e s u l t s to the observed temperatures o f each year as w e l l as to the average  temperatures.  Precipitation Abundant p r e c i p i t a t i o n which i s evenly  distributed  throughout the year i s c h a r a c t e r i s t i c of the G-ulf of Lawrence a r e a . year.  St.  Most s t a t i o n s r e c e i v e more than ko inches a  There i s a s l i g h t  summer maximum i n the more c o n t i n e n t a l  northwestern p a r t of the g u l f and a w i n t e r maximum i n the more maritime southeastern p a r t . the g u l f a r e a , ranging from 60  Snowfall i s f a i r l y h i g h i n  to over 200  inches.  The h i g h e r  t o t a l s are r e c o r d e d along the n o r t h shore and the lower t o t a l s i n the southeastern s e c t i o n .  The e f f e c t  i c e formation and breakup i n the g u l f  of p r e c i p i t a t i o n on  i s minor compared to  t h a t of temperature o r wind. Wind The wind roses the percentage and A p r i l ,  (see maps f o l l o w i n g page 27)  frequencies  of wind by d i r e c t i o n f o r January  which months represent the p e r i o d when i c e i s found  i n the G u l f of S t . Lawrence.  Winds of a w e s t e r l y  p r e v a i l throughout most o f the y e a r ,  time of y e a r the winds are more v a r i a b l e winds occur more f r e q u e n t l y  component  although i n s p r i n g and  summer t h e i r prominence i s l e s s n o t i c e a b l e .  easterly  illustrate  At t h i s  latter  i n d i r e c t i o n and  than at o t h e r  seasons.  Changes i n d i r e c t i o n , even complete r e v e r s a l s , may be  expected  PERCENTAGE FREQUENCY PERCENTAGE  NUMBERS  OF  WIND  INDICATE  4  0  i  2  THE  4  I  ?  (CLIMATIC  PERCENTAGE  MAP  Map  ?  e  OF  6 (to f o l l o w page  OF WIND SUMMARIES,  C A L M S  27)  1948)  w i t h i n very  short p e r i o d s of time due to the c i r c u l a t i o n of  the m i d - l a t i t u d e d e p r e s s i o n s which move a c r o s s the area i n an almost constant p r o c e s s i o n i n w i n t e r . typical  of the b e l t  It  is this  of Westerly Winds, which i s  feature,  responsible  f o r the h i g h l y v a r i a b l e weather c o n d i t i o n s of the g u l f The wind i s e f f e c t i v e  in continually shifting  pack i c e which covers most of the g u l f r o t a t i o n of the e a r t h , the d r i f t  i n winter.  region. the  Due to  the  of f l o a t i n g pack i c e i n the  n o r t h e r n hemisphere i s about t h i r t y degrees to the r i g h t of the wind d i r e c t i o n . westerly  In g e n e r a l terms, however,  winds c a r r y the  the  i c e eastward toward Gabot  w h i l e n o r t h e r l y winds tend t o pack the i c e i n the p a r t of the g u l f . c l e a r i n g of i c e ,  prevailing Strait,  southern  Southerly winds u s u a l l y a c c e l e r a t e but e a s t e r l y  winds h o l d the i c e  the  i n the  gulf.  The sudden changes of wind d i r e c t i o n which are t y p i c a l of r e g i o n cause l o c a l changes i n the p o s i t i o n of pack i c e ,  the  such  as the opening o r c l o s i n g of l e a d s and p o o l s . SUMMARY T i d e s disengage l a n d f a s t i c e formed i n shallow water. the  i c e and break up sheets of  Much of t h i s  ice i s  carried into  open g u l f by t i d a l and ocean c u r r e n t s , adding to  the  supply of i c e which i s l a r g e l y  r e t a i n e d i n the g u l f by the  c o n f i n e d nature of the b a s i n .  The a i r temperatures  enough to preserve t h i s  are low  i c e and t o encourage l o c a l i c e  mation throughout the season.  During t h i s time the  for-  factors  .  causing  . . .  2  i c e movement, p r i n c i p a l l y  much o f t h e i c e s h i f t i n g o c e a n t h r o u g h Cabot  and c a r r y  Strait.  winds and c u r r e n t s ,  keep  some o f i t t o t h e open  q  CHAPTER I I I WINTER ICE CONDITIONS Ice  c o n d i t i o n s i n the Gulf of S t .  Lawrence d u r i n g the  months from November to March are not w e l l known. aerial  No r e g u l a r  survey has been c a r r i e d out and few r e c o r d s taken  aboard s h i p have been p r e s e r v e d . which i s a v a i l a b l e , keepers,  f o r example,  Much of the i n f o r m a t i o n r e p o r t s of s k i p p e r s ,  light-  and other shore o b s e r v e r s , r e f e r s to very l i m i t e d  areas and may not be h i g h l y r e l i a b l e . cussion constitutes  The f o l l o w i n g d i s -  an attempt to present the g e n e r a l p i c t u r e  as i n d i c a t e d by o b s e r v a t i o n s which can be Although c o n d i t i o n s vary g r e a t l y  substantiated.  from y e a r to y e a r ,  only  average c o n d i t i o n s are i m p l i e d . The i s l a n d of Newfoundland a c t s as a b a r r i e r separ a t i n g the G u l f of S t .  Lawrence i c e from the A r c t i c  ice.  The S t r a i t o f B e l l e I s l e admits a q u a n t i t y of i c e which i s sufficient  to f i l l  the n o r t h e a s t arm.  i c e which o r i g i n a t e d as l a n d f a s t Labrador. drift  i c e a l o n g the coast of  Icebergs seldom g a i n entrance to the g u l f ;  they  southward i n the main stream o f the Labrador C u r r e n t .  Consequently, St.  Most of t h i s i s pack  Lawrence  pack i c e c o n s t i t u t e s  the b u l k of the Gulf of  ice.  Winter n a v i g a t i o n In the g u l f  is restricted.  The  C l a r k e Steamship Company operates a w i n t e r s e r v i c e w i t h i c e b r e a k i n g v e s s e l s from Tadoussac to Seven I s l a n d s and sometimes as f a r east as Havre S t .  Pierre.  T h i s i s made p o s s i b l e  by  the  fact  shore. nects  that frequent  In Northumberland  Strait  an  b e t w e e n Cape B r e t o n  a d d i t i o n to  vessels. those  these  The  regular  while  con-  en  closing  the  from the  by  or three  small  area  on  sealing  i n number,  Cape B r e t o n  In  i s carried  c r o s s the  g u l f about the middle  f o l l o w i n g page 32 of navigation  keeping with  assist  gulf  to  occasion-  the  St.  the  i n d i c a t e s the  characteristics the  of  i n most  o f December, o r  earlier.  average date of  at various harbours  the h a r b o u r s n e a r e s t  those  and  n a v i g a t i o n and  ferry  Newfoundland.  t h e whole, c o m m e r c i a l n a v i g a t i o n c e a s e s  sections of map  route  two  a  River. On  that  ice-breaking ferry  services, navigation  ice-breakers,  ships attempting  Lawrence  The  off-  I s l a n d and  C a n a d i a n Government i c e - b r e a k e r s  ally  ice  P r i n c e Edward I s l a n d w i t h t h e m a i n l a n d , and  operates  by  northwest winds push the  i n the  gulf.  the In  c l i m a t e , i t i s apparent  open A t l a n t i c f r e e z e  w h i c h a r e more removed f r o m t h e  later  than  marine i n f l u e n c e .  DECEMBER When t h e part  of the  surface water temperatures  g u l f drop below f r e e z i n g p o i n t d a r i n g  November, i c e b e g i n s in ice  the  shallow  i s very  December.  Isle  t o form  b a y s and  light  and  no  late  to  i n the  confined  In a d d i t i o n to  heavy pack i c e begins Belle  i n the  northeast  arm,  amount f o r m s  i c e p r o d u c e d by  I n December.  late especially  s t r e t c h e s of water.  appreciable  enter  northern  the  until  local freezing,  g u l f through the  In s p i t e  This  of the  fact  Strait that  ice  of  c o n d i t i o n s are not s e r i o u s i n the S t r a i t  of B e l l e I s l e t h r o u g h -  out most of t h i s month, n a v i g a t i o n g e n e r a l l y December  1. Ice forms f a i r l y  R i v e r and estuary because  ceases about  e a r l y i n the lower S t .  Lawrence  and a l o n g the n o r t h shore of the  these areas are removed from the moderating  of the open A t l a n t i c .  Such f a c t o r s  c u r r e n t churn the water,  breaking up the young i c e  as wind, t i d e ,  A large quantity Lawrence estuary  G-aspe C u r r e n t .  sheets these  of i c e broken by t i d a l a c t i o n I n  i s c a r r i e d i n t o the g u l f by  T h i s p r o c e s s begins  in late  the upper reaches of the r i v e r have a l r e a d y t o the  and  they have grown to a t h i c k n e s s which w i l l r e s i s t  attacks. the S t .  influence  Large sheets o f i c e seldom develop  u n t i l January, however.  before  gulf  December  the after  contributed  ice  gulf. Corresponding c l o s e l y w i t h the advent of low a i r  temperatures  throughout the g u l f ,  the f r e e z i n g of harbours  occurs l a t e r  i n the southern and southeastern a r e a s .  here n a v i g a t i o n i s not customary a f t e r week In December. freeze size  the end of the  Even first  Although the Bale de Ghaleur does not  u n t i l the l a t t e r h a l f of the month, due t o the  of the body of water,  the s m a l l e r bays and harbours  a l o n g the western s i d e of the g u l f f r e e z e Ice o r i g i n a t i n g i n the S t .  great  December  15.  Lawrence R i v e r i s c a r r i e d i n t o  the  g u l f by the Gaspe Current and by w e s t e r l y out i n southern areas where constant  before  winds and spreads  c u r r e n t s are  lacking,  f i l l i n g Northumberland S t r a i t by the b e g i n n i n g of January.  The  route through the S t r a i t  n a v i g a t i o n about e n t r a n c e by  late  1,  due  to the b l o c k i n g  i c e , a l t h o u g h the s e c t i o n  m a i n s open. S c o t i a and  January  o f Ganso i s c l o s e d  Many o f t h e h a r b o u r s  of the n o r t h e r n  south of Mulgrave  P r i n c e Edward I s l a n d c o a s t s do n o t f r e e z e  remains  c l e a r throughout  re-  s i t u a t e d a l o n g t h e Nova  December, o r i n some c a s e s , u n t i l  Strait  to  late  until  January.  Cabot  December.  JANUARY  By  January  sufficiently  the water  to give r i s e  Pack i c e formed  temperatures  i n the g u l f  u s u a l l y ; a t t a i n s a thickness of  to four f e e t .  ice  season, Labrador pack i c e i s t h i c k e r ,  siderably  The  Because o f lower temperatures  growlers which  thicker.  winds.  r i d g e s o c c u r most f r e q u e n t l y  which  sheets form  enters the  t h e whole r e g i o n . gulf  The  through the s t r a i t  currents. days, actual  be p i l e d  i n the S t r a i t  of  powerful above  the  feet.  Isle  Such  and  c o a s t , chokes drifts  c o n t r o l l e d by  into the  When t h e d o m i n a n c e o f f l o w I s i n w a r d f o r a  amount i s f a r l e s s  con-  t o g e t h e r w i t h heavy i c e  amount o f i c e w h i c h  more i c e e n t e r s t h e g u l f  to  headlands.  of Belle  from the Labrador  i s largely  one  or f i f t e e n  i n the v i c i n i t y  o f t h e g u l f and, strait  be  o f p r e s s u r e c a u s e d m a i n l y by  o t h e r f o r m i n g a mass a s t h i c k as t w e l v e  t h e n o r t h e a s t arm  sometimes up  a sheet of i c e i s b u c k l e d  S e v e r a l t h i c k n e s s e s o f i c e may  Large  and a l o n g e r  e n t e r t h e g u l f may  Occasionally,  I n t o r i d g e s as a r e s u l t  lowered  to a l a r g e - s c a l e p r o d u c t i o n of i c e .  two  seven f e e t .  have b e e n  up the  tidal few  than a t o t h e r t i m e s , but  t h a n i t w o u l d be  I f t h e r e were  the a  constant  inward c u r r e n t .  Some of t h i s pack i c e d r i f t s  ward i n the weak flow to other s e c t i o n s may be i n c o r p o r a t e d i n t o a l a r g e  of the g u l f where  the w i n t e r .  n o r t h e r l y winds a i d i n d r i v i n g the i c e southward.  A few s m a l l  and g r o w l e r s , which have s t r a y e d from the Labrador  i t becomes plugged w i t h pack i c e .  Newfoundland r e c e i v e s influence  the f u l l b e n e f i t  of the G u l f of S t .  The west coast of  Lawrence.  Consequently,  winter.  but r a t h e r ,  Offshore,  the f l o e s  the n o r t h u n t i l February.  area against  the p r e v a i l i n g northwest offshore,  about c o n s t a n t l y .  attempt n a v i g a t i o n . central gulf  ice  the w i n t e r ,  from  remains  because of  i s covered w i t h pack  Leads are r e a d i l y  but few ships o t h e r than  ice  lee  discovered  ice-breakers  The g e n e r a l movement of the i c e i n the  i s from west to e a s t , under the i n f l u e n c e  p r e v a i l i n g winds and water c u r r e n t s . static  the i n v a s i o n of i c e  possible.  The c e n t r a l p a r t of the g u l f  between the f l o e s ,  effective  winds which c o n t i n u a l l y push the  and r i s k y n a v i g a t i o n i s  which s h i f t s  cemented  The n o r t h shore of the g u l f  c l e a r of pack i c e throughout  St. .  remain i n motion a l l  the northward-flowing eurrent i s  i n defending the c o a s t a l  the  u n t i l January.  George Bay f i l l s w i t h r i v e r i c e which seldom becomes Into a f i e l d ,  strait  of the moderating  harbours a l o n g t h i s coast do not f r e e z e  fairly  at  Frequent  C u r r e n t , may f i n d t h e i r way i n t o the g u l f through the before  it  i c e f i e l d o r s h i f t e d about  the command of wind and wave throughout  icebergs  south-  because the S t .  of  the  C o n d i t i o n s are never  Lawrence R i v e r continues t o  discharge  i n t o the g u l f and new i c e i s forming i n many a r e a s .  35 The i c e Is m o r e . c l o s e l y packed i n the southern p a r t of  the g u l f because  of the decreased c u r r e n t and the c o n -  finement of the b a s i n by the l a n d .  By the middle o f January  Northumberland S t r a i t and George Bay are u s u a l l y f i l l e d w i t h c l o s e pack i c e and the S t r a i t of Canso i s b l o c k e d at northern entrance.  Such a volume of i c e i s swept toward the  c o n s t r i c t i o n of the s t r a i t that i t packs s o l i d and i n t o a compact mass which c o n s t i t u t e s commonly c a l l e d .  The e f f e c t  this  freezes  a " b r i d g e , " as i t  Is  of t h i s b r i d g e i s to prevent  i c e i n George Bay from d r i f t i n g i n t o the in ice-free  the  strait.  the  This r e s u l t s  c o n d i t i o n s south of Mulgrave and n a v i g a t i o n i n .  s t r e t c h i s p o s s i b l e throughout most of the w i n t e r . Pack i c e begins t o emerge from the g u l f  S t r a i t about the middle o f January, but I t and s c a t t e r e d .  In a y e a r of severe  through Cabot  Is u s u a l l y  light  c o n d i t i o n s i c e may be found  as f a r east as Miquelon I s l a n d i n January, as was the case In 1943. field  On t h i s o c c a s i o n , January 24, 1943,  patches  i c e were r e p o r t e d at a p o s i t i o n t h i r t y m i l e s  of  heavy  southwest  of Miquelon. 29 such as 1945,  Conversely,  conditions,  there may be no i c e i n the Cabot S t r a i t  On the average,  area.  Cabot S t r a i t i s p a r t l y covered w i t h i c e  i n g out of the g u l f , to shore.  i n a y e a r of favourable  but i t  stream-  i s never f r o z e n over from shore  Seldom does the i c e extend southward of  Flint  I s l a n d a l o n g the east coast of Cape B r e t o n I s l a n d . 9 u . S. Treasury Department, Coast Guard, I n t e r n a t l o n a l Ice Observation and Ice P a t r o l S e r v i c e i n the North A t l a n t i c Ocean,"Season of 194b, B u l l e t i n NoT 32. Washington, 19*7, P. T 5 ~ " 2  36 The harbours along the Cape B r e t o n east and south coasts freeze  d u r i n g the  second week of January, w h i l e  those  a l o n g the south coast of Newfoundland and that of H a l i f a x are usually ice-free  throughout  the y e a r .  These i c e - f r e e  harbours  are so l o c a t e d t h a t they are p r o t e c t e d from the i n v a s i o n of gulf  ice,  and they are c l i m a t i c a l l y  d a t i o n of l o c a l  favoured i n the  retar-  ice-formation. FEBRUARY  The main exodus of i c e from the g u l f begins February. out.  in  Ice from the c e n t r a l s e c t i o n i s the f i r s t  While Ice  i s l e a v i n g the g u l f  heavy i c e i n the northeast eventually  through Cabot  arm continues t o d r i f t  t o move  Strait, southward,  c l o s i n g on the west coast of Newfoundland as  s o u t h as the Bay of I s l a n d s .  Some of t h i s Ice makes i t s  westward a l o n g the n o r t h shore.  In a d d i t i o n , the S t .  estuary  Consequently,  adds i c e to the s u p p l y .  S t r a i t outflow Is p a r t l y  the  compensated f o r by Inflows  areas and by l o c a l f r e e z i n g ,  far  but the net r e s u l t  way  Lawrence  Cabot In other  Is a l o s s  of  ice. G e n e r a l l y , Cabot S t r a i t closely  on the Newfoundland s i d e . the Ice  closes  Eastward of the  l i g h t e r and s c a t t e r e d ward t o the  56th  In some y e a r s ,  as occured  I n on the Newfoundland coast due to  s u s t a i n e d s o u t h e r l y winds, but t h i s dition.  covered w i t h i c e  packed on the Cape Breton s i d e and f a i r l y open or  scattered i n 1943,  is partly  Is not the u s u a l c o n -  s t r a i t the i c e  i s more open and  s t r i n g s of i c e f r e q u e n t l y  meridian and southward to the  extend  46th  east-  parallel.  37 Occasionally,  northeast winds cause the i c e t o move southwest-  ward along the south coast of Nova S c o t i a , b l o c k i n g  the  harbours. The southern p a r t of the g u l f much o f i t  shifting,  but l i t t l e  stream through Gabot S t r a i t .  remains packed w i t h i c e , .  d e p a r t i n g from the area to  The b a y s ,  i n c l u d i n g the Baie de  Ghaleur and George Bay, are f r o z e n over completely  o r are  f i l l e d w i t h c l o s e l y packed i c e which has been cemented large  sheets p r e s e n t i n g a mosaic appearance.  into  Other areas  are  covered w i t h i c e of a comparable d e s c r i p t i o n , except t h a t there are wide leads between the s h e e t s , p a r t i c u l a r l y Northumberland  Strait.  As e a r l y as F e b r u a r y , t h e r e f o r e , from the g u l f  in  i s inaugurated on a l a r g e  the withdrawal of scale.  ice  This with-  drawal i s the normal r e s u l t of the c o n t r o l of winds and c u r r e n t s and does not i n d i c a t e t h a t the i c e i s m e l t i n g o r b r e a k i n g up due to m i l d weather.  It  i s mainly the c e n t r a l  between A n t l c o s t l I s l a n d and Cabot S t r a i t which c o n t r i b u t e s the i n i t i a l  area to  outflow. SUMMARY  The G u l f of S t . sources,  the S t .  Lawrence r e c e i v e s  Lawrence R i v e r and e s t u a r y ,  coast through the S t r a i t mingles w i t h l o c a l l y i n winter. sections  i c e from two main  of B e l l e I s l e .  and the Labrador  This i c e from o u t s i d e  formed l e e c l o s i n g the g u l f to  The northeast  navigation  arm and the western and southern  of the g u l f are the f i r s t  Then the c e n t r a l area f i l l s  to become  ice-covered.  up and the i c e c l o s e s  the open  3S 8 t r i p a l o n g the west c o a s t of Newfoundland. Ice begins t o emerge from the g u l f the f r i n g e s  the  through Cabot S t r a i t .  of the g u l f are f r o z e n s o l i d ; most of the a r e a  covered w i t h s h i f t i n g pack i c e . more c l o s e l y  Eventually,  The southern p a r t i s  packed, but even here l e a d s  water are found throughout the  winter.  the  and p o o l s o f open  Only is  CHAPTER IV ICE DISTRIBUTION IN THE BREAKUP SEASON DURING THE YEARS 1940-1952 INCLUSIVE, The g e n e r a l i c e c o n d i t i o n s d u r i n g the w i n t e r months indicate that  the c l e a r i n g of the g u l f takes p l a c e  p e r i o d of time and that Strait.  over a l o n g  the i c e l e a v e s p r i m a r i l y through Cabot  With t h i s background the breakup season i s  considered.  The behaviour o f the i c e i n t h i s season of c l e a r i n g can be t r a c e d w i t h some p r e c i s i o n because available  f o r most of the g u l f ,  d e t a i l e d information i s  except f o r the n o r t h e a s t arm.  Although i n f o r m a t i o n concerning the breakup i n the arm i s l a c k i n g ,  i t i s known that  northeast  the i c e n o r t h of a l i n e from  Natashquan to the Bay of I s l a n d s does not d i s c h a r g e Cabot S t r a i t ,  but remains i n the g u l f  u n t i l i t has melted.  The f o l l o w i n g d e s c r i p t i o n of a c t u a l i n March and A p r i l of the years 19^0  through  to 1952,  ice  conditions  inclusive,  based on i n f o r m a t i o n o b t a i n e d by a e r i a l o b s e r v a t i o n . employed were Incomplete concerning A p r i l .  concerning March but were  Appendix. scattered  The d a t a  detailed  This detailed information i n A p r i l  the d e t e r m i n a t i o n of l i m i t s of the main i c e areas at f i e d dates,  enabled speci-  and these l i m i t s are shown on the maps i n the The main i c e areas do not i n c l u d e r e g i o n s of  s t r i n g s and s m a l l patches  of  r e v e a l the temperature  characteristics  f o r the d i f f e r e n c e  widely  ice.  The graphs which accompany the maps are designed  Statistics  is  of the i c e  to  seasons.  from average of the mean  40 monthly temperature were used to achieve these In the ease of the years 1940 t o 1 9 5 ° , twenty-seven  meteorological stations  s t a t i o n s were u s e d . ^ l  i n the Monthly Weather Map5  2  30  inclusive, figures  for  were used i n c o n s t r u c t i o n  o f the graphs, but i n the o t h e r two c a s e s , eighteen  results.  1951  a n <  i  1952,  only  The a b b r e v i a t e d l i s t p u b l i s h e d  was employed Instead of t h a t  the Monthly Record f o r these two y e a r s .  The  in  twenty-seven  s t a t i o n s are i n d i c a t e d on the map f o l l o w i n g page 4 0 , w i t h a d d i t i o n a l ones which were used as replacements of b l a n k s In the r e c o r d .  Those s t a t i o n s  In the event  used f o r the  1951  and 1952 graphs are u n d e r l i n e d . Because the graphs are intended t o show the temperature  c h a r a c t e r i s t i c s of the season over the  a r e a of the g u l f ,  stations  general water  s i t u a t e d on the coast near s e a -  l e v e l were chosen as most r e p r e s e n t a t i v e .  As many  as p o s s i b l e were Included In order t h a t d e v i a t i o n s  stations from  average due to l o c a l causes might be minimized i n company w i t h other s t a t i o n s . ble,  In view of the nature of the i c e d a t a a v a i l a -  a breakdown of temperatures In v a r i o u s p a r t s of the  was deemed unwarranted, consequently,  the s t a t i o n s  l o c a l i d e n t i t y and r e p r e s e n t p o i n t s i n the Gulf of  lose  gulf their  St.  partment of T r a n s p o r t , M e t e o r o l o g i c a l D i v i s i o n , Monthly Record (monthly s t a t i s t i c s s e r i e s ) . Toronto,  1940-1950":  ^ T h e r e d u c t i o n In number of s t a t i o n s i n these years was n e c e s s i t a t e d because the Monthly Record had not yet reached the p u b l i c a t i o n s t a g e . ^Department of T r a n s p o r t , M e t e o r o l o g i c a l D i v i s i o n . Monthly Weather Map (monthly weather map s t a t i s t i c s s e r i e s ) . T o r o n t o , I95I-I952T  Lawrence area as a whole. The h o r i z o n t a l a x i s , temperature of every  symbolic of the average  s t a t i o n i n the g u l f r e g i o n , although the  averages may d i f f e r . difference  z e r o , Is  Each dot r e p r e s e n t s one s t a t i o n .  from average at  each s t a t i o n i n whole  Fahrenheit i s found along the v e r t i c a l a x i s ;  each  The  degrees station  r e c o r d i n g an average monthly temperature which i s above  its  a l l - t i m e average i s l o c a t e d above the zero l i n e , while each one r e c o r d i n g a below average temperature line.  i s found below the  I f the f i g u r e f o r a s t a t i o n c o i n c i d e s w i t h the  to the nearest degree,  average,  the dot i s p l a c e d on the zero l i n e .  I t must be emphasized that t h i s chapter i s p r i m a r i l y a p r e s e n t a t i o n of d a t a .  F u r t h e r i n t e r p r e t a t i o n of the ma-  t e r i a l w i l l be found In f o l l o w i n g s e c t i o n s .  The maps f o r  each season are designed t o accompany the t e x t and should be c o n s u l t e d i n conjunction w i t h  it.  SEASON OF 1940 During March there was a c o n s i d e r a b l e a r e a of open water i n the g u l f ,  p a r t i c u l a r l y i n the c e n t r a l s e c t i o n along  the steamer t r a c k . 2 3 the southern h a l f , and numerous l e a d s .  A g r e a t d e a l o f c l o s e pack i c e l a y  in  a l t h o u g h there were p o o l s of open water The exodus through Gabot S t r a i t was i n  progress.  ^The "steamer t r a c k " i s the d i r e c t route from Gabot S t r a i t to the S t . Lawrence estuary south of A n t i c o s t i I s l a n d which i s f o l l o w e d by most ocean v e s s e l s .  42 By e a r l y A p r i l the i c e was m e l t i n g and b r e a k i n g up i n the western p a r t of the g u l f .  The open channel a l o n g the  steamer t r a c k had widened, but the passage through Cabot on the Newfoundland s i d e remained c o n s t r i c t e d .  The Bale de  Ghaleur was c l e a r i n g a l o n g the n o r t h e r n s i d e . Strait  and the east coast  similarly,  Northumberland  of P r i n c e Edward I s l a n d were open;  there was open water In the v i c i n i t y  Magdalen I s l a n d s .  The Ice was c o n f i n e d ,  e a s t e r n h a l f of the g u l f  Strait  of  the  essentially,  at the middle of  to  the  April.  The b u l k of the Ice had withdrawn from the g u l f by A p r i l 25 when the main f i e l d l a y o f f c o a s t s of Cape Breton I s l a n d .  Shortly after  month the route through the S t r a i t v i a East P o i n t became open.  the east and south the middle of  the  of Ganso, George Bay, and  Some s c a t t e r e d  i c e which, c o n s t i -  t u t e d a danger to n a v i g a t i o n remained i n Northumberland S t r a i t u n t i l the end of A p r i l .  The f i e l d o f f  of Cape B r e t o n covered a r e l a t i v e l y  but i t  Gn the whole, this  season of 194-0.  width of Cabot  Strait.  The c l e a r i n g proceeded  remaining i c e of any  the Gape Breton  The graphs I n d i c a t e in spite  revealing  The breakup was w e l l under way i n March  from west to east and the l a s t quence was found o f f  St.  i c e c o n d i t i o n s were not severe d u r i n g  and was a c c e l e r a t e d d u r i n g A p r i l .  average,  as f a r as  shrank q u i c k l y i n the l a s t week,  open water a c r o s s the f u l l  coast  l a r g e area d u r i n g much  o f A p r i l and reached along the south coast Esprit,  the east  that  of the f a c t  the  that  conse-  coast. season was warmer than  two months, November and  April,  were d e f i n i t e l y  below normal.  average than any of the other months. that  March was n e a r e r the The m i l d w i n t e r assured  i c e c o n d i t i o n s would not be severe by p r e v e n t i n g the  from becoming unduly t h i c k or  ice  extensive.  SEASON OF 1941 Close pack i c e covered about h a l f of the g u l f March, 1941, water, the  although there were some l a r g e patches  especially  in  of open  between A n t i c o s t l I s l a n d and Gaspe and i n  southern p a r t of the g u l f .  The Cabot S t r a i t r e g i o n was  choked up w i t h c l o s e pack i c e which extended a great  distance  southeastward. The western p a r t of the g u l f was mainly c l e a r by A p r i l 5, except f o r i c e I n . t h e Baie de Chaleur and t h i s was moving out q u i c k l y . a l o n g the east coast moved to the  As i n 1940,  open water was found  of P r i n c e Edward I s l a n d .  e a s t e r n s i d e of the g u l f where I t  steamer t r a c k and completely  The Ice had covered  f i l l e d Cabot S t r a i t . the f i e l d was unusually  because  i n the g u l f was great  of i c e  c l e a r i n g took p l a c e r a p i d l y . B r e t o n east  the  Eastward  and southward of the s t r a i t the q u a n t i t y  ice  extensive  and the  The i c e was packed on the  Cape  coast.  By the middle of A p r i l the i c e had receded from the central section,  opening a narrow passage through Cabot  and along the steamer r o u t e .  Along the east coast  B r e t o n the Ice had moved offshore the f i e l d remained e x t e n s i v e . Bay,  and the S t r a i t  w i t h westerly  Strait  of Gape  winds,  Northumberland.Strait,  but George  of Ganso opened d u r i n g the t h i r d week of  the month, although i c e c l u n g to the west coast u n t i l n e a r l y the end of A p r i l . Strait,  The f i e l d outside  which was s t i l l o f f s h o r e ,  and d i s a p p e a r e d s h o r t l y a f t e r . St.  of Gape B r e t o n Gabot  had c o n t r a c t e d by A p r i l  Between Heath P o i n t and Cape  George the i c e l i n g e r e d u n t i l e a r l y May. The breakup was w e l l advanced by the end of the  week i n A p r i l cally  in this  c l e a r by May 1.  C o n s i d e r i n g the q u a n t i t y  breakup was reasonably  swift  o f i c e which  more than i n l$HO,  the  and f o l l o w e d a normal p a t t e r n .  The i c e made i t s way from west to east and passed Cabot S t r a i t  first  season and the whole a r e a was p r a c t i -  had to be e x p e l l e d from the g u l f ,  that  25  through  i n the same manner as i t had done i n 19^0,  the s t r a i t  and the steamer t r a c k were i c e - c o v e r e d  a l a t e r date and the g r e a t e r  except until  volume of i c e was spread over a  wider a r e a beyond the s t r a i t . > Temperatures  i n the g u l f a r e a were near average In  November, but were d e f i n i t e l y January.  below average i n December and  February temperatures were remarkably h i g h ,  those of March and A p r i l were n e a r e r normal.  The f a c t  while that  the i c e was h e a v i e r than i n 1940 was probably due t o the temperatures  lower  i n December and January. SEASON OF 1942  The i c e was l e s s  extensive  i t had been the year b e f o r e . throughout March and A p r i l p a r t of the g u l f . began opening f i r s t  d u r i n g March, 194-2, than  Frequent n o r t h e r l y  s h i f t e d the i c e to the  As i n previous y e a r s ,  winds southern  the Bale de Ghaleur  a l o n g the n o r t h e r n s i d e .  It  appears  4 likely  that t h i s p a t t e r n of c l e a r i n g i s c h i e f l y  the i s l a n d s which narrow the mouth of the bay.  5  determined by Open water  extended  southward from the Baie de Ghaleur i n t o Northumberland  Strait.  The steamer t r a c k was c l e a r ,  1941,  u n l i k e the c o n d i t i o n i n  and there was an open route through Cabot S t r a i t on the  Newfoundland s i d e .  Beyond the s t r a i t  the n o r t h e r l y winds  had c a r r i e d the i c e f a r southward a l o n g the south coast of Nova S c o t i a . The s o u t h e r l y movement of the i c e continued t h r o u g h out A p r i l under the Influence  of n o r t h e r l y winds.  A shore,  l e a d along the n o r t h coast of P r i n c e Edward I s l a n d was p i n c h e d out by the middle of the month. the  The Improvement  in  southern s e c t i o n where the i c e f i e l d s had c o n t r a c t e d by  A p r i l 15  was p a r a l l e l e d by the i n v a s i o n of an e x t e n s i v e  field  from the n o r t h which covered, a l a r g e p a r t of the steamer  track.  A f t e r the middle of A p r i l the i c e was slow In rounding Cape North and tended to remain i n the r e g i o n of George Bay. . During l a t e A p r i l the f i e l d south of A n t l c o s t i still Strait  constituted a hazard.  Island  Although George Bay and the  of Ganso had been c l e a r on A p r i l 25,  c l o s e pack  was d r i f t e d i n t o the bay by winds a few days l a t e r ,  ice  closing  n a v i g a t i o n u n t i l the i c e withdrew on May '3 and e v e n t u a l l y  made  i t s way up the west coast of Gape B r e t o n and around Cape North.  The south coast of Cape B r e t o n was c l e a r  throughout  A p r i l because there were no s o u t h e r l y winds powerful to push the i c e on shore.  enough  4-6 At  the beginning o f A p r i l the breakup was  sufficiently  advanced t o i n d i c a t e an e a r l y opening of a l l n a v i g a t i o n r o u t e s . Much of the g u l f was s e c t i o n , was the  open and the i c e , c o n f i n e d to the southern  l o o s e l y d i s t r i b u t e d over a wide a r e a .  f l o w of Ice through Cabot S t r a i t was  However,  r e s t r i c t e d by  n o r t h e r l y winds and the i c e accumulated along the west coast of  Gape B r e t o n .  In a d d i t i o n , a l a r g e f i e l d encroached on the  steamer t r a c k south of A n t i c o s t l I s l a n d and d i s p e r s e d very slowly.  As a r e s u l t , the p a t t e r n of breakup d i f f e r e d from  t h a t of the p r e v i o u s two years i n the f a c t that the i c e d i d not  drift  f r e e l y from west t o east, t a k i n g advantage  f u l l width of Cabot S t r a i t as an e x i t .  of the  Rather, i t stagnated  i n the southern s e c t i o n and clogged the George B a y - S t r a i t o f Ganso a r e a u n t i l e a r l y In the of  May.  r e s p e c t to temperature, November and January were  only months which were d i s t i n c t l y below average.  The  rest  the months were warmer than normal, March In p a r t i c u l a r  when temperatures ranged from three t o t e n degrees above average.  The December, March, and A p r i l temperatures were  h i g h e r than i n 194-1  which accounted f o r the l i g h t e r i c e  c o n d i t i o n s experienced e a r l y i n the season. SEASON OP Most o f the g u l f was In many areas the i c e was  194-3  i c e - c o v e r e d throughout March.  c l o s e l y packed, e s p e c i a l l y i n the  B a l e de Chaleur, around Gape Breton I s l a n d , and i n Gabot Strait.  Outside the s t r a i t the southward and eastward  e x t e n s i o n o f the i c e was  g r e a t e r d u r i n g the l a t t e r h a l f o f  March than d u r i n g the f i r s t h a l f .  T h i s c o n d i t i o n was  a normal  r e f l e c t i o n of the a c c e l e r a t i o n of the c l e a r i n g d u r i n g breakup season.  Because w e s t e r l y winds prevented  c l o s i n g i n on the south coast of Cape Breton, E a r l y i n A p r i l t h e r e was pack Ice i n the g u l f . although  i t was  The  the i c e from  i t remained c l e a r .  s t i l l a great d e a l of open  steamer t r a c k was  unnavigable,  opening south of A n t i c o s t i I s l a n d .  Little  improvement had taken p l a c e i n the Baie de Chaleur. the Magdalen I s l a n d s the i c e was was  George Bay,  East  With frequent  withdrawing northward from  l e a v i n g the S t r a i t of Canso and the bay  open.  T h i s northward movement of the i c e continued A p r i l and l e d to the e a r l y c l e a r i n g o f the s e c t i o n of the g u l f .  of  very open, but Cabot S t r a i t  s t i l l p a r t l y f i l l e d w i t h c l o s e pack I c e .  s o u t h e r l y winds the i c e was  the  through  southeastern  Close pack i c e remained i n c e n t r a l  r e g i o n s and along the steamer t r a c k , however, u n t i l . l a t e i n April.  The  f a c t that the i c e moved northward b l o c k i n g the  mouth of the Bale de Chaleur was breakup of the bay. Gape Breton  Gabot S t r a i t began t o open f i r s t  s i d e as the i c e receded  unusual p a t t e r n of c l e a r i n g was winds.  The  and  from the c o a s t .  caused mainly by  retarded on  the  This  southerly  g u l f c l e a r e d r a p i d l y d u r i n g the l a s t few days of  A p r i l and the steamer t r a c k was 30.  r e s p o n s i b l e f o r the  navigable  Some Ice remained u n t i l e a r l y May  throughout on  In the Baie de  April  Chaleur  o f f the west coast of Newfoundland. . The' 1943 breakup f o l l o w e d q u i t e a d i f f e r e n t p a t t e r n  from those of the p r e c e d i n g  three y e a r s .  i n the main body of the g u l f was  In t h i s season i c e  more abundant.  It cleared  4g first  i n the a r e a east of G-aspe' P e n i n s u l a , then i n the  e a s t e r n p a r t of the g u l f ,  and l a s t  s e c t i o n a l o n g the steamer r o u t e .  of a l l , i n the  south-  central  The main c o n t r i b u t i n g f a c t o r  i n t h i s withdrawal was the frequent  occurrence of  southerly  winds. In the matter of temperature d u r i n g the i c e season,  it  i s apparent t h a t below normal c o n d i t i o n s p r e v a i l e d i n every month except November and February. d e c i d e d l y warmer than average,  Only February.was  while December, January, March,  and A p r i l were c o n s i d e r a b l y c o l d e r than average.  These lower  temperatures l e d to the occurrence In t h i s season of wides p r e a d , heavy  i c e , much of which was c l o s e l y SEASON OF  packed.  1944  The breakup proceeded w i t h r a p i d i t y d u r i n g March. Although the i c e was f a i r l y extensive  e a r l y In the month,  s t r o n g northwest and west winds opened up the i c e the g u l f and c a r r i e d i t  throughout  eastward t o feed a broad stream of  i c e d r i f t i n g through Gabot S t r a i t .  A narrow passage remained  open on the Newfoundland s i d e d u r i n g most of the month, probably owing to the inward c u r r e n t .  The southward and e a s t -  ward l i m i t s of the i c e o u t s i d e the s t r a i t approximated those of A p r i l 5«  *  n  l a t e March the e a s t e r n p a r t of the  steamer  t r a c k c l e a r e d and the i c e receded from the whole west of the g u l f ,  except i n the Bale de C h a l e u r .  d i s p e r s a l may be a t t r i b u t e d , c h i e f l y , winds.  coast  This rapid  to s u s t a i n e d northwest  By A p r i l 5 the i c e had withdrawn to the Cape Breton Island region.  Close pack i c e i n Northumberland S t r a i t and  George Bay b l o c k e d the route through the S t r a i t reached up the west coast 1941,  of Cape B r e t o n .  As i n 1940  and  the east coast of P r i n c e Edward I s l a n d was open.  evidence  supports the c o n c l u s i o n t h a t  southeast  are c l e a r e d r e a d i l y by northwest winds. partly  of Canso and  This  coastal  areas  Gabot S t r a i t remained  i c e - c o v e r e d and the i c e i n the d i s p e r s a l a r e a was  u n u s u a l l y extensive quantity  as a r e s u l t of the presence  of i c e which l e f t  Cape Breton east coast  of a l a r g e  the g u l f d u r i n g March.  the  Along the  i c e was i n s h o r e , f i l l i n g  Sydney  harbour. Northumberland S t r a i t had l a r g e l y middle of A p r i l .  Southwest  northward on A p r i l 15,  c l e a r e d by the  winds moved the i c e i n George Bay  r e n d e r i n g the route n a v i g a b l e ,  but  n o r t h e r l y winds caused i t  to invade the bay again on A p r i l  o b s t r u c t i n g the passage.  In the Baie de Chaleur the Ice had  opened and was d i s p e r s i n g , l i m i t s had changed l i t t l e  i n spite  of the f a c t  s i n c e A p r i l 5.  that  winds.  its  The f i e l d i n Cabot  S t r a i t and beyond was d i m i n i s h i n g and had receded Gape Breton coast w i t h southwest  17,  from.the  As a r e s u l t ,  Sydney  harbour c l e a r e d . Most of the g u l f was c l e a r by A p r i l 25 w i t h e x c e p t i o n of Ice  i n George Bay and the S t r a i t  prevented n a v i g a t i o n u n t i l A p r i l 27, of  Gape B r e t o n .  Cabot.Strait,  Some f i e l d s  the  of Canso,  which  and along the west  coast  of Ice remained o f f s h o r e  but these were d i s i n t e g r a t i n g  rapidly.  beyond  50 The p a t t e r n of breakup i n 1944 resembled that  of  194-2  i n certain respects.  There was a wide a r e a of open water on  A p r i l 5 i n each case,  but the c o n d i t i o n s d u r i n g March were  different. visible  In the one i n s t a n c e ,  1942,  i n March, while i n the o t h e r ,  extensive  but c l e a r e d r a p i d l y .  invaded by Ice at a l a t e The temperatures r e t a r d ice formation.  much open water was 1944,  the i c e had been  In b o t h cases George Bay was  date owing t o n o r t h e r l y winds. of the autumn were h i g h enough to  December and January were i n  contrast;  the f i r s t was w e l l below average and the second was w e l l February temperatures A p r i l were lower. so severe  were near normal, but those  The f a c t  that the Ice  of March and  c o n d i t i o n s were not  as i n the year before would suggest that  temperatures  were h i g h e r , which was the  above.  the  case.  SEASON OF 1945 The season of 1945 was s i n g u l a r i n i t s p a u c i t y of owing to m i l d w i n t e r temperatures. which d i d e x i s t gulf.  was segregated  D u r i n g March the  ice  i n the southern p a r t of  the  George Bay was f i l l e d with c l o s e pack i c e which  ex-  tended up the west coast the i c e was f a i r l y open.  of Gape B r e t o n I s l a n d ,  elsewhere,  The flow of Ice through Cabot  S t r a i t was very l i m i t e d i n amount and was c o n f i n e d to a narrow b e l t  on the Cape Breton s i d e .  c l o s e d d u r i n g the month. f i e l d reached i t s  The s t r a i t was never  In the d i s p e r s a l r e g i o n the  ice  g r e a t e s t extent d u r i n g e a r l y March, then  i t d i m i n i s h e d r a p i d l y d u r i n g the l a t t e r p a r t of the. month.  ice,  51 T h i s f i e l d was of l e s s e r dimensions than those years.  of  previous  Only on one o c c a s i o n , at the middle of March, d i d the  i c e move onshore along the south coast of Cape Breton i n the vicinity  of L o u i s b u r g , but t h i s i n c u r s i o n , caused by  winds, was  short-lived.  The g u l f was p r a c t i c a l l y week i n A p r i l .  c l e a r by the end of the  The only i c e remaining was i n the  C h a l e u r , around the Magdalen I s l a n d s , the west coast of Gape B r e t o n . quickly,  by A p r i l 6.  c o a s t had almost completely of  i n George Bay, and a l o n g  Most of t h i s  The f i e l d o f f  first  Bale-de  i c e moved out  r e n d e r i n g the route through the S t r a i t of  navigable  easterly  Canso  the Cape Breton east  d i s s i p a t e d and l e f t  only a s t r i p  i c e near s h o r e . The whole season of 1945  conditions.  w  a  s  c h a r a c t e r i z e d by m i l d  ice  Ice was l a t e In forming In the f a l l and was never  very e x t e n s i v e d u r i n g the w i n t e r ,  consequently,  and f i n a l c l e a r i n g occured remarkably e a r l y . breakup was s i m i l a r to t h a t of 1944, i c e Involved was much l e s s . v i a a route l y i n g on the I n s i d e the g u l f  the  breakup  The p a t t e r n of  although the amount o f  The i c e departed from the  southern s i d e of Gabot  gulf  Strait.  i t l i n g e r e d i n three p a r t i c u l a r areas a  l o n g e r than i n o t h e r s , the Magdalen I s l a n d s ,  ,  little  the Bale de C h a l e u r , the v i c i n i t y  of  and the George Bay r e g i o n .  E x c e p t i o n a l l y h i g h temperatures  throughout the  were mainly r e s p o n s i b l e f o r these clement i c e  season  conditions.  A l l months, except December, were c o n s i d e r a b l y warmer, than average and even December was s l i g h t l y  warmer than normal..  SEASON OF 1946 Little  i n f o r m a t i o n was a v a i l a b l e  d i t i o n s i n March.  It  i s e s t a b l i s h e d t h a t there were wide  areas of open water i n many s e c t i o n s the month.  concerning i c e c o n -  of the g u l f  throughout  P r e v a i l i n g northwest winds d u r i n g March l e d t o  the removal of a c o n s i d e r a b l e q u a n t i t y of i c e through Cabot Strait..  The steamer t r a c k was almost c l e a r at the end o f  the month. By A p r i l 5 the t r a c k was n a v i g a b l e w i t h patches and s t r i n g s of l o o s e i c e and the western p a r t of the g u l f was clear.  Northumberland S t r a i t was navigable from the western  entrance to P i c t o u I s l a n d .  The m a j o r i t y  of the i c e i n the  g u l f l a y i n the southeastern s e c t i o n along the n o r t h coast P r i n c e Edward I s l a n d and the west coast  of Cape Breton I s l a n d .  George Bay and the S t r a i t of Canso were unnavigable. Cabot S t r a i t a narrow s t r i p of i c e was p r e s s e d c l o s e the l a n d and the coast.  of  In against  ice was inshore a l o n g the Cape Breton east  The i c e f i e l d beyond the s t r a i t reached f a r southward,  but i t s eastward extent was more l i m i t e d .  Frequent  northeast,  winds d u r i n g A p r i l undoubtedly caused t h i s southward d r i f t o f the  ice. The f i e l d s g r a d u a l l y d i m i n i s h e d throughout the  rest  of A p r i l without any d r a s t i c a l t e r a t i o n s of t h e i r p o s i t i o n s , a l t h o u g h i n m i d - A p r i l a tongue of i c e was t h r u s t  southward  a l o n g the Nova S c o t i a south coast by e a s t e r l y winds.  George  Bay c l e a r e d i n the l a t t e r h a l f of the month, e n a b l i n g the  commencement of n a v i g a t i o n on that  route.  It was not  the l a s t week of A p r i l t h a t the i c e i n the f i e l d o f f  until the west  coast o f Cape Breton opened up and rounded Cape North to d i s s i p a t e "beyond Gabot S t r a i t . remained by May 1.  Only a few patches  of  Ice  -  During the w i n t e r of 1946 a moderate q u a n t i t y of appeared i n the g u l f ,  ice  but r a p i d c l e a r i n g o c c u r r e d i n March.  Throughout A p r i l the withdrawal of the i c e proceeded more slowly,  i n a manner s i m i l a r to i t s behaviour i n 1942.  In b o t h  cases n o r t h e a s t winds p r e v a i l e d d u r i n g A p r i l which drove the ice  southward and tended to discourage i t s f r e e  through Gabot  movement  Strait.  The f i r s t f o u r months of the 1946 i c e season were c h a r a c t e r i z e d by temperatures near the average.  March  temperatures were somewhat h i g h e r than normal and A p r i l temperatures were s l i g h t l y  lower.  The s i t u a t i o n w i t h r e g a r d  t o i c e was not i n c o n s i s t e n t w i t h these d a t a . age temperature c o n d i t i o n s i n d i c a t e t h a t  The near a v e r -  this particular  season may have experienced near average amounts of  ice.  SEASON OP 1947 The i c e i n the g u l f d u r i n g March was more than i t was the year b e f o r e . of open water,  extensive  Although there were few areas  one of which l a y a l o n g the east coast  of  P r i n c e Edward I s l a n d , the Ice opened up a great d e a l In March, especially  a l o n g the steamer t r a c k .  The flow through Cabot  S t r a i t was not e x c e s s i v e and the i c e f i e l d beyond the was u n u s u a l l y  contracted.  strait  E a r l y i n A p r i l a l a r g e a r e a i n the g u l f was ice-covered,  but much of the i c e was open and s c a t t e r e d .  was customary first  i n former y e a r s ,  a l o n g the northern s i d e .  c l e a r e d d u r i n g the  through the S t r a i t gable at t h i s  The steamer t r a c k and a s t r i p i n c l u d i n g Northumberland  second week of A p r i l .  The route  of Canso and George Bay a l s o became  time.  As  the Baie de Chaleur c l e a r e d  i n the southwestern p a r t of the g u l f , Strait,  still  navi-  In tne d i s p e r s a l r e g i o n the f i e l d was  very l i m i t e d i n extent and a shore l e a d e x i s t e d a l o n g the northeast  coast  of Cape B r e t o n .  s o u t h e r l y winds were e f f e c t i v e o f the g u l f e a s t coast  O c c a s i o n a l p e r i o d s of i n c l e a r i n g the southern p a r t  r e a d i l y and i n m a i n t a i n i n g a shore l e a d along the of Gape B r e t o n .  The c e n t r a l s e c t i o n of the g u l f between the Magdalen I s l a n d s and P r i n c e Edward I s l a n d where the i c e was cleared after at t h i s t i m e .  A p r i l 15.  scattered  Cabot S t r a i t was e s s e n t i a l l y  clear  Toward the end of the month the f i e l d o f f  the  Cape Breton west coast broke up and began moving r a p i d l y around Cape North.  The f i e l d o f f  the east coast  from shore and the i c e d i s p e r s e d s h o r t l y the  retreated  afterwards.  North of  steamer t r a c k some i c e remained u n t i l May. The breakup p a t t e r n of 1947  t o that  of 1941.  d u r i n g March. gulf,  D  o  r  e  The Ice was reasonably It  cleared f i r s t  a  close  resemblance  extensive  i n the western p a r t of  the  along the steamer r o u t e , and i n Northumberland S t r a i t  and George Bay, then i n the c e n t r a l a r e a , and l a s t a l o n g the west coast of Gape B r e t o n , n o r t h of the track,  and heavy  and i n the d i s p e r s a l r e g i o n .  of a l l , steamer  A s i m i l a r i t y was a l s o evident temperatures  of the two y e a r s .  both years.  The f i r s t  i n the i c e  February was u n u s u a l l y warm i n  t h r e e months of the 19^7  season were  c o l d e r than normal and A p r i l was c o l d e r s t i l l . F e b r u a r y , was above average, extensive  i n spite  of i t ,  season  March,  although the i c e was  SEASON OF  formation.  19^8  At the middle of March the whole g u l f was  t h e r e was l i t t l e  ice-covered.  packed In the southern p a r t ,  open water anywhere.  Beyond Cabot  the i c e was spread over a tremendous a r e a .  Strait  strong  winds and s e v e r a l areas opened s u f f i c i e n t l y  open water,  p a r t i c u l a r l y a l o n g the steamer t r a c k .  narrow shore l e a d e x i s t e d Cape A n g u i l l e .  but  C l e a r i n g proceeded  r a p i d l y d u r i n g the l a t t e r h a l f of the month w i t h westerly  fairly  thus i n d i c a t i n g that low e a r l y  w i n t e r temperatures are c r i t i c a l i n i c e  The i c e was more c l o s e l y  like  i n Cabot S t r a i t o f f  The l i m i t s of the f i e l d i n the  to  reveal  A very  Gape Ray and dispersal  r e g i o n had receded to the p o s i t i o n s where they remained throughout  April.  The speedy withdrawal of the i c e frorm west to east c o n t i n u e d i n A p r i l a i d e d by strong n o r t h w e s t e r l y  gales.  Much  o f the western p a r t of the g u l f was c l e a r e a r l y i n the month, except f o r the Bale de Ghaleur which was c l o s e l y packed on the southern s i d e .  The e a s t e r n p a r t of the steamer  was s t i l l c l o s e d by i c e ,  track  although the narrow shore l e a d  remained a l o n g the Newfoundland c o a s t .  S i m i l a r l y , the  B r e t o n east coast was c l e a r throughout the month.  Cape  56 Northumberland S t r a i t and George Bay were opening up, but were not c l e a r u n t i l the t h i r d week of A p r i l . which had been c l e a r on A p r i l 5 scattered  i c e that  w  a  s  The S t r a i t of Ganso  a d m i t t i n g a flow of  impeded n a v i g a t i o n .  Toward the end of A p r i l the i c e was mainly c o n f i n e d to the Gape B r e t o n a r e a .  Gabot S t r a i t was l a r g e l y  and the f i e l d beyond o c c u p i e d an a r e a as great A p r i l 15.  The i c e , which had been o f f s h o r e  was d r i v e n on the coast  ice-covered as that on  throughout  April,  on A p r i l 27 by strong n o r t h e a s t  l e a v i n g Cabot S t r a i t e s s e n t i a l l y  open.  Here the  winds,  field  remained u n t i l I t loosened up and d i s p e r s e d a f t e r Hay 9 w i t h westerly this  winds.  Sydney harbour was completely  blocked  until  date. The l a r g e q u a n t i t y  of i c e i n the g u l f e a r l y  breakup season c l e a r e d r a p i d l y , g a i n i n g e x i t Strait.  It  i n the  through Gabot  occupied most of the s t r a i t during*March and A p r i l .  The i c e withdrew from west to east i n a normal manner and vacated the George Bay a r e a before the Gape B r e t o n n o r t h and east c o a s t a l a r e a s .  However, the i c e  in this  last-mentioned  r e g i o n moved onshore at the end of A p r i l and d i d not u n t i l the second week of May. sembled t h a t  of 1941,  Essentially,  except that  clear  the breakup r e -  the Cape Breton r e g i o n  was encased by i c e u n t i l an e x c e p t i o n a l l y  late  date.  Temperatures were above average i n November and January, near average i n December, and d i s t i n c t l y average i n F e b r u a r y , March, and A p r i l . w i n t e r temperatures were s l i g h t l y  below  Although the  above average,  early  there  was  57 a great amount of heavy i c e i n t h i s of low e a r l y w i n t e r temperatures SEASON OF  season.  The importance  i s reduced by t h i s 1949  In the season of I949 the i c e was somewhat than the y e a r b e f o r e , The majority  fact.  nevertheless,  It  lighter  covered a wide a r e a .  of the i c e was i n s i d e the g u l f on the March  the steamer t r a c k east of the B i r d Rocks as w e l l as S t r a i t was c l e a r , patches of l o o s e  and beyond the s t r a i t ice only.  15;  Cabot  there were a few  By March 25 the i c e had moved  eastward under the i n f l u e n c e  of northwest winds, c o v e r i n g  steamer t r a c k and a l l but c l o s i n g Cabot S t r a i t , shore l e a d around Cape Ray. B r e t o n east coast to S c a t a r i .  the  except f o r a  I t had d r i f t e d along the  Cape  Accompanying t h i s movement was  a withdrawal of i c e from the Gaspe c o a s t .  The c l e a r i n g of  the  Baie de Chaleur was In p r o g r e s s , w i t h the i c e moving out of the n o r t h e r n h a l f .  Other p a r t s of the g u l f remained  Ice-  covered. Great improvement had taken p l a c e by A p r i l 5' most notable was the r e t r e a t of the g u l f  of the  s c a t t e r e d and open i c e fairly  n  i c e from the western  and the opening of the steamer t r a c k .  the steamer route was n a v i g a b l e ,  T  e  part  Although  t h e r e was c o n s i d e r a b l e ,  i n the a r e a .  Gabot S t r a i t  Itself  was  open, but the f i e l d outside the s t r a i t had been d r i v e n  onshore a l o n g the east and south c o a s t s of Gape B r e t o n by northerly  winds.  By the middle of A p r i l the Baie de Chaleur was and most o f Northumberland S t r a i t was open, while  clear  scattered  i c e was strewn over the steamer t r a c k , gable.  George Bay and the west coast  ice-covered, south coast  but were s w i f t l y  although i t was n a v i of Gape B r e t o n were  clearing.  the i c e had moved o f f s h o r e .  Along the Gape B r e t o n A l l these areas  c l e a r by the end of the t h i r d week of A p r i l .  the east- coast  of Gape Breton and s c a t t e r e d  The i c e season was not severe c l e a r i n g began i n earnest  few t r a c e s 1940, the  after  the i c e  A p r i l 25.  T h i s season may be compared w i t h  in  although  19^9.  remarkably h i g h temperatures. degrees  temperatures  were nearer  iee  behind  i c e c o n d i t i o n s were due, i n p a r t ,  four or f i v e  speedily  Moving from west to e a s t , the  f o r the breakup f o l l o w e d a s i m i l a r p a t t e r n ,  The l i g h t  widely.  Once the  through Gabot S t r a i t and l e f t  i c e was much l i g h t e r  located  a f t e r March 15 i t proceeded  and i n an o r d e r l y f a s h i o n . departed from the g u l f  i n 1949.  were  Finally,  n o r t h e r l y g a l e s on A p r i l 25 broke up the e n t i r e f i e l d off  still  to  A l l months except February were  above average at many s t a t i o n s .  February  average.  SEASON OF 1950 During March, 1950,  the flow of i c e through Cabot  S t r a i t was i n c o n s i d e r a b l e volume.  S e v e r a l areas were open  toward the end o f the month; among them were the western  part  of the steamer t r a c k and the r e g i o n from the Bale de Ghaleur t o Northumberland S t r a i t . covered.  The r e s t  of the g u l f was  Gabot S t r a i t was f i l l e d w i t h i c e and the  o u t s i d e was unusually extensive i c e and the moderately  because  icefield  of the abundance of  r a p i d r a t e of c l e a r i n g d u r i n g March.  59 The steamer t r a c k was e s s e n t i a l l y  c l e a r hy A p r i l  except f o r a tongue of i c e which was t h r u s t a c r o s s i t Gape A n g u i l l e by n o r t h e r l y winds.  5*  near  Frequent n o r t h e r l y winds  were p a c k i n g the i c e i n the southern p a r t of the g u l f .  The  Baie de Ghaleur was opening along the n o r t h e r n s i d e and Northumberland S t r a i t was p a r t l y c l e a r .  D r i f t i c e was  over much of the c e n t r a l s e c t i o n of the g u l f . the i c e o c c u p i e d only the southern h a l f , d i s p e r s a l r e g i o n remained e x t e n s i v e . been offshore  strewn  In Gabot  Strait  but the f i e l d i n the  Although the i c e had  along the east coast of Gape Breton on A p r i l  i t moved onshore a few days  3>  later.  By A p r i l 15 the Ice was compacted In the  southeastern  s e c t i o n of the g u l f and In the d i s p e r s a l r e g i o n , w i t h the e x c e p t i o n of a broad band of i c e which had been  drifted  southward a c r o s s the steamer route by the n o r t h e r l y winds. The Baie de Ghaleur had l a r g e l y Dalhousle.  George Bay, however,  c l e a r e d and was n a v i g a b l e was f u l l  of i c e and the  S t r a i t of Ganso was d i s c h a r g i n g i c e southward i n t o Atlantic.  Glose pack Ice  close  the  covered the p a r t of Gabot  between Cape North and S t .  Paul I s l a n d .  to  Strait  The i c e was  still  i n s h o r e along the east coast of Cape Breton and, i n  a d d i t i o n , the f i e l d had moved a g r e a t d i s t a n c e o c c u p i e d the  south c o a s t a l  southward and  area.  Toward the end of the month n o r t h e r l y winds h e l d the i c e In the southeastern p a r t of the g u l f , flow around Gape N o r t h .  restricting  the  The steamer t r a c k had c l e a r e d and  the f i e l d beyond Cabot S t r a i t had d i m i n i s h e d , but a great  deal  6o o f l e e remained i n s i d e the g u l f which must e v e n t u a l l y i n the area of d i s p e r s a l .  The c l e a r i n g of the  p a r t of the g u l f was g r a d u a l ; the S t r a i t entirely  southeastern  of Canso was not  c l e a r f o r n a v i g a t i o n u n t i l May 7 and the i c e  a l o n g the Gape Breton coast around Gape North the i c e constituting  a danger to  The i c e i n t h i s heavy.  arrive  lingered  u n t i l the middle of May.  Once  spread over a wide a r e a , no l o n g e r navigation.  season was reasonably  extensive  and  The p a t t e r n of c l e a r i n g d u r i n g A p r i l was more from  n o r t h t o south than from west to e a s t .  N o r t h e r l y winds were  mainly r e s p o n s i b l e f o r the accumulation of the i c e southeastern p o r t i o n of the g u l f .  These c o n d i t i o n s  those of 19^-2 when the i c e seemed to  resembled  stagnate i n t h i s  but the s i t u a t i o n was worse i n 1950 because  area,  the i c e was more  abundant and the f i n a l c l e a r i n g was postponed even Concerning temperature,  i n the  longer.  December and January were  the only months which were warmer than average.  The  latter  p a r t of the season was c o l d e r , w i t h February and March much c o l d e r than average.  These c o n d i t i o n s approximated those  19kg and l e n d weight to the a s s e r t i o n that l a t e  of  winter  temperatures which are w e l l below average may l e a d to an abundance  of  ice. SEASON OF I95I  The season of 1951 larity .  d i s p l a y e d a most p e c u l i a r i r r e g u -  Throughout the season the i c e was segregated  western p a r t of the g u l f .  At the end o f the f i r s t  i n the  week i n  61 March there was p r a c t i c a l l y no i c e east of the 62nd m e r i d i a n . West of t h i s meridian the i c e was open i n the c e n t r a l and c l o s e l y  packed near shore.  d i s p e r s e d i n the offshore  section  As March progressed the  a r e a s , w h i l e i t remained  packed along the New Brunswick c o a s t ,  ice  closely  i n Northumberland S t r a i t ,  and along the n o r t h shore of P r i n c e Edward I s l a n d . Strong and s u s t a i n e d n o r t h e a s t March and A p r i l w e r e . d i r e c t l y  and east winds through  r e s p o n s i b l e f o r the  o f i c e along the west shore of the g u l f .  accumulation  By A p r i l 5 the  field  n o r t h of P r i n c e Edward I s l a n d was d i s a p p e a r i n g and the Bale de Ghaleur was opening along the n o r t h e r n s i d e . Northumberland S t r a i t was c l e a r . Ice  took p l a c e  Most of  A southward movement of  i n the second week of A p r i l when the wind  became more n o r t h e r l y , l e a v i n g the r e g i o n o f f Baie de Ghaleur c l e a r of I c e . winds f i n a l l y the g u l f  the  the mouth of  On A p r i l 16 b r i s k  loosened up a l l the i c e  and i t d r i f t e d seaward.  the  westerly  i n the southern p a r t o f  By A p r i l 25 the only  Ice  o b s t r u c t i n g n a v i g a t i o n was l o c a t e d In Northumberland S t r a i t , but i t  d i s s i p a t e d before  the end of the month.  The p a t t e r n of breakup i n 1951 any of the p r e v i o u s t e n seasons. lenient  in this  was not p a r a l l e l e d by  The i c e c o n d i t i o n s were  season as they were i n 19^5.  as  The main  d i s t i n c t i o n between the seasons l a y  i n the f a c t t h a t the  which entered the g u l f from the S t .  Lawrence R i v e r was packed  a l o n g the New Brunswick coast by e a s t e r l y  ice  winds, r a t h e r than  c a r r i e d through to Gabot S t r a i t by w e s t e r l y  winds.  c o n c e n t r a t i o n of i c e along t h i s coast had.the  The  additional  '62 effect  of r e t a r d i n g the breakup of the Bale de Ghaleur.  the i c e d i s p e r s e d i t navigation  s c a t t e r e d widely  i n other a r e a s .  and the S t r a i t  When  and d i d not h i n d e r  The routes through Gabot  Strait  of Canso were c l e a r throughout March and A p r i l .  The i c e  season was remarkably m i l d , perhaps  m i l d e s t of the years examined.  Temperatures were, s e v e r a l  degrees above average i n every month. g u l f was i c e - f r e e  A great p a r t of  throughout the season, and i t  t h a t t h e i c e was e x c e p t i o n a l l y 1  the  is  the  definite  light.  SEASON OP  1952  The whole c e n t r a l s e c t i o n o f the g u l f was c l e a r by middle of March and the main i c e a r e a was i n the portion.  southern  Much of t h i s a r e a was covered w i t h c l o s e pack  N o r t h e r l y winds through February and March d r i f t e d the southward.  The fl'ow of i c e through Gabot S t r a i t  toward the end of March w i t h the s t r a i t  the  ice. ice  increased  h a l f c o v e r e d , but  the  i c e was of l i m i t e d extent beyond. In e a r l y A p r i l the Bale de Ghaleur continued to a l o n g the n o r t h e r n s i d e ,  and Northumberland S t r a i t  Bay were b e g i n n i n g to open up. even f u r t h e r southward.  clear  and G-eorge  Most of the i c e had r e t r e a t e d  Off the east coast of Gape Breton the  i c e had spread over a l a r g e r area and had moved onshore, encroaching on the south c o a s t . A p r i l were l i g h t  Because the winds d u r i n g  and v a r i a b l e i n d i r e c t i o n , they d i d not  the i c e to o t h e r regions or encourage from the  gulf.  also  shift  i t s q u i c k withdrawal  The c l e a r i n g p r o g r e s s e d g r a d u a l l y ,  r e s u l t i n g i n more  areas of open water by the middle of the month, around P r i n c e Edward I s l a n d .  especially  Cabot S t r a i t was mainly open  and the i c e beyond had receded from the Gape B r e t o n By the end of A p r i l the i c e f i e l d s  coast.  had shrunken, but  a b l e i c e remained as a formidable o b s t a c l e  to  consider-  navigation.  C l o s e pack i c e covered the eastern h a l f of George Bay and much of  the S t r a i t  region.  of Canso, as w e l l as the Gape Breton west  The d r i f t i c e  i n the e a s t e r n h a l f of Northumberland  S t r a i t prevented n a v i g a t i o n v i a t h i s r o u t e . winds on A p r i l 24 were e f f e c t i v e  Strong  and s t r i n g s .  northwest  i n c l e a r i n g the east and  south c o a s t s of Gape B r e t o n , l e a v i n g only a few patches  coastal  George Bay and the S t r a i t  scattered of Canso were  not c l e a r u n t i l May 3 and some Ice l i n g e r e d In Northumberland S t r a i t f o r another week. The breakup of 1952 years  earlier.  early date,  was s i m i l a r to that  of 1942,  ten  In both years the g u l f began c l e a r i n g at an  but i c e remained i n the  southern s e c t i o n s  e a r l y May, b l o c k i n g the S t r a i t of Canso r o u t e .  until  The r e t a r -  d a t i o n of the breakup was t o be a t t r i b u t e d p r i m a r i l y to n o r t h e r l y winds, which packed the i c e i n the s o u t h , and t o the l a c k o f s u s t a i n e d p e r i o d s of s o u t h e r l y o r w e s t e r l y which would have a c c e l e r a t e d  the  exodus.  The records of temperature was above average i n t h i s r e s p e c t .  winds,  i n d i c a t e that  the  season  November and December were  n e a r e r average than the o t h e r f o u r months which were  above.  The i c e was more extensive  season  than i n 1951,  was s t i l l l i g h t e r than normal.  °ut the i c e  CHAPTER V THE NATURE OF THE BREAKUP AND THE DETERMINING FACTORS PATTERNS AND RATES OF BREAKUP It  Is apparent from the examination of the maps of  ice  c o n d i t i o n s In the G u l f of S t . Lawrence t h a t the p a t t e r n and r a t e of breakup v a r i e s immensely from year to y e a r . theless,  Never-  the fundamental d r i f t of the i c e i s from west to  Cabot S t r a i t ,  c o n s t i t u t i n g the main o u t l e t  the d e s t i n a t i o n of most of the i c e , n o r t h e a s t arm.  from the g u l f ,  east. Is  except f o r t h a t i n the  D e v i a t i o n s of the i c e from the most d i r e c t  r o u t e to Cabot S t r a i t , which are caused by numerous f a c t o r s , are r e s p o n s i b l e f o r the d i f f e r e n t  p a t t e r n s and r a t e s of  breakup. In Most years there are c e r t a i n areas which become f r e e of i c e before o t h e r s .  A t r i a n g u l a r region off  c o a s t of Newfoundland, w i t h the apex at Cape Ray, ice-free  is  the  south  generally  throughout the year and a passage around Cape Ray and  Cape A n g u l l l e Is open most of the t i m e .  The c e n t r a l p a r t of  the g u l f northwest of Gabot S t r a i t d i s c h a r g e s  i c e i n January  o r F e b r u a r y , but i t continues to r e c e i v e more from other s e c t i o n s and, as a r e s u l t , become c l e a r ,  although i t  it  i s seldom the f i r s t  area t o  c l e a r s b e f o r e the southern p a r t .  The s t r e t c h south of A n t i c o s t i I s l a n d appears to open f i r s t , then the western s e c t i o n and the steamer r o u t e , and f i n a l l y , the southeastern s e c t i o n and the d i s p e r s a l r e g i o n .  6 While i c e remains i n the Bale de Chaleur a f t e r area outside side.  it  i s usually  Northumberland S t r a i t  east coast its  is clear,  the  southern  c l e a r s from west to east and the  of P r i n c e Edward I s l a n d tends to open e a r l i e r than  surroundings.  S i m i l a r l y , the a r e a immediately  Magdalen I s l a n d s f r e q u e n t l y the  confined to the  south coast  occasionally  only.  differentiate  opens e a r l y .  east o f  Although these g e n e r a l f e a t u r e s  the seasons  p a t t e r n s and r a t e s of  of most seasons,  it  Ice  of  the  is possible  on the b a s i s of s e v e r a l  withdrawal.  w i t h two e x c e p t i o n s .  these seasons the  1941,  During  the i c e d r i f t e d from west to east and v a c a t e d i n a normal course of w i t h -  The Bale de C h a l e u r , Northumberland S t r a i t ,  Bay, and the S t r a i t of Canso were c l e a r before the r e g i o n , and open water appeared o f f Edward I s l a n d at an e a r l y  date.  the coast  Generally,  George  dispersal  of P r i n c e  the steamer  was not c l e a r much i n advance of the southern r e g i o n s . a l l but the two seasons o f 1940 west coast  and 1949,  In  some i c e along  A l s o , i n the case of 1941  the i c e l i n g e r e d unduly l a t e  steamer t r a c k . consistent  track  the  of Cape Breton was slow i n rounding Gape N o r t h , but  the delay was not l e n g t h y . 1947,  two  The f i r s t group comprises  1945, 1947, 1948, and I949.  southern p a r t of the g u l f  drawal.  to  recurrent  The t h i r t e e n seasons may be d i v i d e d roughly Into  the years 1940,  the  Chedabucto Bay and  of Cape Breton are encroached upon by  breakup are c h a r a c t e r i s t i c  categories,  5  Otherwise,  pattern.  and  i n the r e g i o n n o r t h of  the  the breakups f o l l o w e d a reasonably  66 The r a t e of c l e a r i n g was f a i r l y r a p i d throughout March and A p r i l d u r i n g these seasons. of i c e present was a d e c i d i n g f a c t o r of  its  complete disappearance.  was p r a c t i c a l l y  Of course,  c l e a r by the f i r s t  the amount  i n determining the  F o r example,  i n 19^5>  of A p r i l ,  while i n  rates  The breakup of 194-2  from t h e , r e s t  end of A p r i l , Breton.  i n that  then the i c e l i n g e r e d on the west coast  stagnating  differed  reasonably southern  gulf.  194-6, 1950,  and 1952,  which witnessed  of  19^2,  such.stagnation  as f a i l e d to occur i n the years d i s c u s s e d p r e v i o u s l y . remained a l o n g the west coast late  dates.  of Cape Breton u n t i l  In most c a s e s ,  u n t i l a l l but the southeastern of i c e ,  the c l e a r i n g  Ice  exception-  progressed  s e c t i o n of the g u l f was  then the process o f c l e a r i n g slowed and the  appeared to  the  of Gape  i n the  The second group i n c l u d e s the i c e seasons  ally  actual  i t progressed r a p i d l y u n t i l  d i r e c t and at a r a p i d pace, without  1944,  the  The movement of the i c e i n these years was  p a r t of the  gulf  19^7,  In s p i t e of t h i s ,  slightly  date  the  i t was not c l e a r u n t i l e a r l y May. of breakup were comparable.  both  free  ice  stagnate.  Although the steamer t r a c k was f r e q u e n t l y advance of the southern a r e a s ,  clear in  i c e from the n o r t h was  thrust  southward a c r o s s the route i n 1942 and 1 9 5 ° ,  hindering  navigation  As a r u l e ,  u n t i l after  the middle of A p r i l .  the  flow of i c e through Gabot S t r a i t was r e s t r i c t e d i n A p r i l , l e a v i n g the s t r a i t p a r t l y open. Strait  opened before  p l a c e to c l e a r .  U s u a l l y , Northumberland  George Bay, but i n 1952  The east coast  i t was the  of P r i n c e Edward I s l a n d  last  generally  c l e a r e d before  but i n 1946  the Cape Breton side of the  i t was b l o c k e d l a t e  most of the month.  In A p r i l a f t e r b e i n g  except i n 1944.  d i s p l a y e d some of the c h a r a c t e r i s t i c s it  clear  On the other hand, the n o r t h coast  i s l a n d was slow In c l e a r i n g ,  however,  strait,  of  This  season  of the f i r s t  group,  d i f f e r e d from them p a r t i c u l a r l y i n i t s  rate  the  of  breakup. In r e s p e c t  to r a t e s  of breakup, the i c e i n these  became s l u g g i s h toward the end of the season.  Rapid c l e a r i n g  d u r i n g March f o l l o w e d by gradual withdrawal i n A p r i l was experience  of the seasons  of 1944 and 1946.  of c l e a r i n g p r e v a i l e d i n 1942 and i n 1950, r a t e was not so swift the f a c t  that  i c e seasons  The 1952  the  A s i m i l a r rate except that  the  season d i f f e r e d  the withdrawal was slow i n both months.  i n t h i s second group, t h e r e f o r e ,  i z e d by an e a r l y stagnation  i n March.  years  were  in  The  character-  spurt of c l e a r i n g f o l l o w e d by a p e r i o d of  and accumulation of the i c e i n the  s e c t i o n of the g u l f .  The route v i a the S t r a i t  George Bay was b l o c k e d u n t i l l o n g a f t e r  -  southeastern of Canso and  the steamer  track  was open. The two years which were not i n c l u d e d i n e i t h e r of these groups f o l l o w q u i t e d i f f e r e n t 1943, off  breakup p a t t e r n s .  In  the i c e began c l e a r i n g i n George Bay at the south and  A n t i c o s t i I s l a n d i n the n o r t h .  The i c e i n the  western  p a r t of the g u l f r e t r e a t e d from b o t h the n o r t h and south to accumulate it  In the c e n t r a l a r e a .  shifted offshore.  L i k e w i s e , around Cape Breton  During much of A p r i l the i c e  streamed  through Cabot S t r a i t , result,  filling  i t from shore to s h o r e .  As a ,  the steamer t r a c k was b l o c k e d u n t i l l a t e i n A p r i l ,  but the S t r a i t of Canso route was open remarkably e a r l y . Bale de Ghaleur was l a t e i n c l e a r i n g . the r a t e of breakup was s w i f t pecially  throughout  i n view of the great q u a n t i t y  the g u l f t h a t  On the whole,  The  however,  the season,  es-  of i c e which l a y  in  winter.  The other e x c e p t i o n a l y e a r was 1951•  In many p a r t s  o f the g u l f which are u s u a l l y i c e - c o v e r e d d u r i n g the s p r i n g t h e r e was v i r t u a l l y no i c e .  Accumulation had o c c u r r e d i n  the western p a r t of the g u l f . fields  d i s p e r s a l took p l a c e ,  On the o u t e r f r i n g e s  of  l e a d i n g to t h e i r c o n t r a c t i o n ,  but the main body of the i c e remained as i f pinned the western s i d e .  During the f i r s t h a l f of A p r i l  moved south and f i n a l l y month.  the  d i s i n t e g r a t e d before  the  ice  the end of  Because the c l e a r i n g proceeded g r a d u a l l y  areas were not invaded by l a r g e f i e l d s  against  the  the  eastern  dangerous t o n a v i -  g a t i o n , but r a t h e r , remained open throughout the breakup. The r a t e of c l e a r i n g was slow d u r i n g b o t h March and A p r i l . These c o n d i t i o n s which p r e v a i l e d i n I95I were remarkable,  definitely  i f not unique. THE DETERMINING FACTORS OF THE BREAKUP  The behaviour o f the i c e i n a l l phases o f  its  formation and breakup i s c o n t r o l l e d by the p h y s i c a l o f the environment. previously,  Many of these f a c t o r s  but i t i s necessary  were  factors  indicated  to re-examine them i n the  light  of an understanding of the i c e  conditions.  The aim of  t h i s d i s c u s s i o n s h a l l be to determine the r e l a t i v e o f each  influence  factor. The N o n - V a r i a b l e F a c t o r s The i n f l u e n c e  appreciably  of some of these f a c t o r s  from year to y e a r ;  termed n o n - v a r i a b l e .  does not  vary  for^ t h i s reason they may be  Those which are d i s c u s s e d are  s u b a e r i a l and submarine morphology,  the t i d e s  the  and t i d a l  c u r r e n t s , and the ocean c u r r e n t s . S u b a e r i a l and Submarine Morphology Because i c e f o r m a t i o n takes p l a c e more r e a d i l y where the water i s  shallow,  l o c a l i c e i s more l i k e l y t o  i n the southern p a r t of the g u l f than elsewhere. not i c e forms i n great although i t  quantity  i s suspected that  harbours throughout the g u l f do f r e e z e if  only f o r a short t i m e .  shallow,  as In t h i s  i s produced.  i s unknown,  The bays and  over d u r i n g the  southern r e g i o n , a great q u a n t i t y  Among the bays which f r e e z e  such as George Bay,  winter,  Where the bays are broad and  C h a l e u r , M i r a m l c h i Bay, and Gaspe Bay. bays,  Whether o r  i n the open g u l f  i t does n o t .  originate  it  is possible  of  ice  are the Bale de  In the that  wide-mouthed some i c e formed  i n other areas f i n d s i t s way i n t o the bays and i s  cemented  i n t o a s o l i d sheet before  Other  l o c a l ice  covers them.  r e g i o n s of l o c a l i c e formation are the shallows Northumberland S t r a i t  and around the Magdalen  in  Islands.  70 The g u l f  i a so shaped that  the southern p a r t a c t s as  a b a s i n of accumulation i n t o which i c e i s d i v e r t e d as i t from west to e a s t .  If  Gape Breton I s l a n d were removed,  g u l f would become I c e - f r e e it  i s the r e l a t i v e  clearing.  much e a r l i e r than i t does  can escape through the  toward t h i s opening. f a r worse i f  the of  constricted  The S t r a i t of B e l l e I s l e i s a l s o narrow and,  i n a d d i t i o n , other f o r c e s  discourage  the mass movement of  Cabot S t r a i t were as narrow as e i t h e r the Its  existence  Strait  makes  the withdrawal of most of the Ice to d i s s i p a t e  the open A t l a n t i c ,  ice  On the other hand, c o n d i t i o n s would be  o f B e l l e I s l e o r the S t r a i t of Canso.  until it  because  The i c e tends to p i l e up a l o n g the west coast  of Canso.  possible  the  narrowness of the o u t l e t which r e t a r d s  Cape Breton and l i t t l e Strait  moves  otherwise,  the  in  i c e would remain i n the  gulf  melted. W i t h i n the main southern b a s i n are s m a l l e r bays and  bights  which tend to d e t a i n the i c e .  the n o r t h coast  of P r i n c e Edward I s l a n d where the  c r a d l e d throughout the w i n t e r . whieh serves Strait  Ice  of  is  A g a i n , there i s George, Bay  as an overflow b a s i n f o r i c e i n Northumberland  even a f t e r  often funnels  There i s the b i g h t  the bay has c l e a r e d .  In t u r n , George Bay  i c e i n t o the S t r a i t of Canso.  And f i n a l l y ,  i s the Bale de Ghaleur which always c l e a r s f i r s t n o r t h e r n s i d e , mainly because  along  the mouth on the southern  there  the side  Is o b s t r u c t e d by Shippigan and Miscou i s l a n d s . The Magdalen I s l a n d s , constitute  obstacles  the B i r d Rocks, and B r i o n I s l a n d  i n the path of i c e movement by  splitting  71 the l a r g e r sheets of i c e which move toward Cabot  Strait.  A n t i c o s t i I s l a n d serves as a p a r t i t i o n s e p a r a t i n g the i c e which originates  i n the.St.  Lawrence R i v e r from that which comes  from the n o r t h e a s t arm.  Most of t h i s  i c e from the r i v e r  a l o n g the Gaspe coast and reaches the g u l f without detainment because the coast Is smooth.  drifts  suffering  During seasons when  the i c e moves southward P r i n c e Edward I s l a n d  protects  Northumberland S t r a i t w i t h the r e s u l t that the s t r a i t  opens  e a r l i e r than other southern r e g i o n s . The c o n t r o l l i n g Influence  of the l a n d o b v i o u s l y  determines the boundaries w i t h i n which the i c e may move and indicates  the routes by which the i c e  may withdraw.  p r o v i d e s a framework which i s n o n - v a r i a b l e i n i t s W i t h i n t h i s framework o t h e r f o r c e s the  affect  It  function.  the behaviour of  ice.  T i d e s and T i d a l Currents One of these f o r c e s associated  t i d a l current.  i s the t i d a l f o r c e ,  with  its  The d i s t u r b a n c e of the water  the most important i n f l u e n c e  is  exerted by the t i d a l u n d u l a t i o n ,  while the t i d a l c u r r e n t s s h i f t  the i c e back and f o r t h and  are r e s p o n s i b l e f o r a c e r t a i n amount of mass movement. Landfast Is f r e q u e n t l y  i c e which forms a l o n g shores and over  s h a t t e r e d by the t i d a l s w e l l and i s  o f f s h o r e by t i d a l c u r r e n t s o r winds as pack i c e . occurs commonly i n the e a r l y . w i n t e r , range  of t i d e  i s great.  The S t .  especially  shoals  carried This  where  Lawrence e s t u a r y ,  the  with  its  h i g h range of t i d e , must he the source o f l a r g e  quantities  of i c e because  and c a r r y  the t i d e s  and c u r r e n t s disengage  away the i c e as f a s t as i t  i s produced.  This e f f e c t  is  not  so pronounced i n the v i c i n i t y of the Magdalen I s l a n d s due to the s m a l l range of t i d e  here.  In Northumberland S t r a i t the t i d a l c u r r e n t s are reasonably  s t r o n g and the range of t i d e  most s e c t i o n s  of the g u l f .  i s h i g h e r than In  These f o r c e s  are s u c c e s s f u l  p r e v e n t i n g the formation of a continuous sheet. h e r e , and elsewhere  i n the g u l f ,  i c e e s t a b l i s h themselves the  i c e i s kept  i n motion.  Nevertheless,  narrow s t r i p s of  along the s h o r e s .  in  landfast  Outside the  strips  In the bays which do freeze  over,  M i r a m i c h i Bay, Bale de Ghaleur, and Gaspe Bay, among o t h e r s , the s w e l l does not enter with e f f e c t i v e n e s s of  i c e has s o l i d i f i e d .  decaying,  however,  and s h a t t e r s  sheets.  is  The t i d a l c u r r e n t s i n the  T r a n s p o r t a t i o n of great q u a n t i t i e s  Strait  originates.  of i c e i s  effected  When the wind blows i n the same d i r e c t i o n  as the c u r r e n t f l o w s , velocity.  sheet  i t s dominant p o s i t i o n  o f Canso f l u s h out the i c e before an i c e - c o v e r  by t i d a l c u r r e n t s .  the  During the s p r i n g when the i c e  the t i d e r e g a i n s  the i c e  after  Ice may be c a r r i e d along at a h i g h  Then, i f the wind continues  i n the same d i r e c t i o n  when the c u r r e n t i s r e v e r s e d , the v e l o c i t y  may be reduced and  only p a r t of the i c e w i l l r e t u r n t o i t s  original position.  T h i s type of movement occurs f r e q u e n t l y  In Northumberland  Strait,  the S t r a i t of Canso, and o t h e r areas where  c u r r e n t s are reasonably  strong.  tidal  Considerable i c e i s  ushered  Into the g u l f the S t r a i t  and e x p e l l e d from I t hy the t i d a l c u r r e n t i n  of B e l l e I s l e ,  because  t h e r e appears to be a domi-  nant flow one way or the other f o r extended p e r i o d s of Although the whole n o r t h e a s t up w i t h i c e ,  the s t r a i t does not f r e e z e  Briefly, gulf  arm o f the g u l f becomes  the e f f e c t  i s to break up the i c e  of t i d e s  areas,  thereby  stopped  completely.  and t i d a l c u r r e n t s i n the  sheets i n t o pack i c e and to  inaugurate movement of the pack. i n the formation of great  over  time.  T h i s process o f t e n  quantities  i n c r e a s i n g the t o t a l  o t h e r hand, through a g i t a t i o n  of i c e i n  results  favourable  amount of I c e .  On the  of the water the t i d e s  retard  the f o r m a t i o n of Ice and prevent widespread c o n s o l i d a t i o n of sheet  ice.  Ocean C u r r e n t s The system of constant definitely  a major f a c t o r  c u r r e n t s i n the g u l f  is  i n c o n t r o l l i n g the movement of  Ice.  An Immense volume of i c e i s c a r r i e d i n t o the g u l f from the St.  Lawrence R i v e r by the Gaspe c u r r e n t .  When the  velocity  of the c u r r e n t i s reduced o f f the mouth of the Bale de Chaleur the i c e  i s cast f r e e from the stream and spreads  i n the southern p a r t of the g u l f .  A slower d r i f t  still  p r e v a i l s which c a r r i e s some i c e toward the Magdalen and Cabot S t r a i t . the i c e f i n d s  In s p i t e  cross-gulf  flow,  i t s way i n t o the southern b a s i n of the  which e v e n t u a l l y  fills  A constant the g u l f ,  of t h i s  out  Islands much o f gulf  up.  current off  Cape N o r t h d i s m i s s e s  but i t s power i s l a r g e l y  wasted d u r i n g the  ice  from  early  w i n t e r beeause quantity  i t i s not s u p p l i e d w i t h i c e i n any  great  u n t i l that from the west reaches Cabot S t r a i t .  t h e r e were a current of comparable v e l o c i t y  If  j o i n i n g the G-aspe  and Cape B r e t o n c u r r e n t s the i c e from the r i v e r would be conducted d i r e c t l y  i n t o the A t l a n t i c ,  but such i s not the  On the Newfoundland side of Cabot S t r a i t i n t o the g u l f . coast  the c u r r e n t  flows  The g e n e r a l westward d r i f t along the  south  case.  of Newfoundland and the inward flow around Gape Ray tend  t o r e p e l the i n v a s i o n of i c e from the n o r t h and west. result,  these areas are f r e q u e n t l y  As a  c l e a r throughout the  season.  S i m i l a r l y , the northward d r i f t and c u r r e n t along the west coast fall  of Newfoundland keeps that  and c l e a r s i t  offshore.  coast  open l a t e r i n the  e a r l i e r i n the s p r i n g than the  area  In the n o r t h e r n p a r t of the g u l f the c u r r e n t s are  i l l - d e f i n e d and of low v e l o c i t y , a g e n e r a l westx^ard movement.  although there appears to be  This d r i f t  a i d s the  spreading  o f i c e from the northeast arm. W i t h i n the p h y s i o g r a p h i c framexirork of the g u l f  the  c u r r e n t s and g e n e r a l movements f u r t h e r d e f i n e  the  constant  d i r e c t i o n s i n which the l e e may move and i n d i c a t e the where the  areas  i c e may s t a g n a t e . Variable Factors  The f a c t o r s  t r e a t e d In t h i s  by annual v a r i a b i l i t y .  discussed.  characterized  The p h y s i c a l p r o p e r t i e s of the  and the m e t e o r o l o g i c a l f a c t o r s and wind are  s e c t i o n are  of temperature,  water  precipitation  75 P h y s i c a l P r o p e r t i e s of the Water As was p o i n t e d out p r e v i o u s l y , o f the water i n many p a r t s of the g u l f favourable factors  temperatures  r e a c h a p o i n t which i s  to the i c e formation p r o c e s s ,  but due to  other  i c e formation i s not as widespread as might be  The presence effect  the surface  of imported i c e  of r e d u c i n g surface  expected.  i n a g i v e n a r e a w i l l have  temperatures  the  i n that v i c i n i t y .  undoubtedly occurs i n the g u l f and may account f o r i c e  This  for-  mation i n an a r e a where i c e would not o r i g i n a t e  otherwise.  But on the whole,  are not w e l l  known, i t  is  although surface  suspected that  y e a r to year as a r e s u l t are m e t e o r o l o g i c a l  temperatures  they do not vary a p p r e c i a b l y  of i n f l u e n c e s  i n nature.  breakup of the i c e .  other than those which  The surface water  i s r a i s e d by the same m e t e o r o l o g i c a l  temperature  f a c t o r s which cause  The r e l a t i o n s h i p between these  o f water temperatures  from  the  factors  and weather c o n d i t i o n s i s c l o s e  enough  to permit the d i s r e g a r d of surface water temperatures  i n view  o f the l a c k of I n f o r m a t i o n .  factors  exert they  t h e i r influence exert  i n d i r e c t l y i n respect  it directly  Meteorological It  While the m e t e o r o l o g i c a l  on the i c e i n the  to i c e  formation,  breakup.  Factors  i s the m e t e o r o l o g i c a l f a c t o r s  of the  environment  which are the main cause o f annual v a r i a t i o n i n i c e ditions.  The c l i m a t e ,  meteorological average i c e  which r e p r e s e n t s  conditions,  conditions.  can be j u s t l y  con-  the average of  the  compared only w i t h  T h e r e f o r e , an i n v e s t i g a t i o n  of  the  a c t u a l weather c o n d i t i o n s which p r e v a i l e d i n the years i s necessary  thirteen  i n o r d e r to determine the causes of the  v a r i a t i o n i n these i c e seasons.  Such an i n v e s t i g a t i o n p r o p e r -  l y r e q u i r e s a d e t a i l e d examination of the d a i l y s y n o p t i c  charts  over a four-month p e r i o d i n each of the t h i r t e e n y e a r s , t o g e t h e r w i t h a c a r e f u l study of the are kept on f i l e Toronto. present  s t a t i o n r e c o r d s which  at the M e t e o r o l o g i c a l D i v i s i o n o f f i c e s  in  T h i s task was not undertaken i n connection w i t h the study. The aim of the i n v e s t i g a t i o n s  t h a t were c a r r i e d out  was to e s t a b l i s h a g e n e r a l r e l a t i o n s h i p between i c e c o n d i t i o n s i n the breakup season and the main f e a t u r e s weather,  of  namely, temperature, p r e c i p i t a t i o n and wind.  study was c o n f i n e d to the use of p u b l i s h e d s t a t i s t i c s ,  The except  i n the case of the examination of s y n o p t i c c h a r t s to determine wind d i r e c t i o n s and f o r c e s . ness,  frequency  The e f f e c t s  of s u n s h i n e , c l o u d i -  of depressions or o t h e r a i r mass phenomena  were not i n v e s t i g a t e d .  Nevertheless,  the f o l l o w i n g  evaluation  should e s t a b l i s h a g e n e r a l r e l a t i o n s h i p which might form the b a s i s f o r a more exhaustive Temperature.  and d e t a i l e d  study.  The r e l a t i o n s h i p s between the mean  monthly temperatures at a number of s t a t i o n s St.  i n the Gulf of  Lawrence a r e a d u r i n g the i c e season and the i c e  distri-  b u t i o n d u r i n g the breakup were i n d i c a t e d f o r each year previously. a definite  C o n s i d e r i n g a l l the y e a r s examined, as a group, r e l a t i o n s h i p can be e s t a b l i s h e d . .  The f o l l o w i n g  d i s c u s s i o n c o n s i d e r s temperature i n r e l a t i o n to the  pattern  77 o f breakup, the r a t e of breakup, the time of f i n a l and the q u a n t i t y and extent of To f a c i l i t a t e advantageous  ice.  comparison w i t h the i c e c o n d i t i o n s i t  is  to d i v i d e the seasons i n t o groups on the b a s i s of  t h e i r temperature c h a r a c t e r i s t i c s  (see Table I I ,  Four main groups can be i s o l a t e d . of the years 1940, 1945,  page gg).  The f i r s t group, made up  1949, I95I, and 1952,  is characterized  by above average temperatures i n the i c e season. i s d e f i n e d on the b a s i s of the f a c t months, e s s e n t i a l l y ,  1942,  i n common are 1944,  three. 194g,  The t h i r d  three months are  The y e a r s which have t h i s  and 1950.  has only one r e p r e s e n t a t i v e  three  t h r e e , and  1946, and I947.  Just the o p p o s i t e i n that the f i r s t  warmer than the l a s t  The second  that the f i r s t  are c o l d e r than the l a s t  I n c l u d e s the years 1941, group i s  clearing,  feature  F i n a l l y , the f o u r t h group  i n the y e a r 19^3.  *  n  t h i s case  the temperatures of the i c e season were below average.  Within  these main groups there are s u b d i v i s i o n s which I n d i c a t e more specifically  the d i f f e r e n c e s between the y e a r s ;  these are  d e f i n e d on the accompanying t a b l e . The p a t t e r n of breakup i s reasonably independent of the i c e season temperatures.  While t h e r e are two cases where  the p a t t e r n of breakup i s s i m i l a r i n two years of l i k e temperature c o n d i t i o n s , namely, groups 2A and 2B, there no i n s t a n c e i n the f i r s t  three main groups where a l l the  o f one group witnessed the same p a t t e r n of breakup.  is years  Nor does  the r a t e of breakup seem t o be c o n t r o l l e d by temperatures In the i c e season.  There does not appear to be any  consistent  r e l a t i o n even w i t h i n subgroups, although a g a i n , i n group 2B  7«§ the same r a t e of breakup p r e v a i l e d i n each y e a r .  On the o t h e r  hand, group IB i s c h a r a c t e r i z e d by two opposite r a t e s of breakup. The time of f i n a l c l e a r i n g i s understood as r e p r e s e n t i n g the time when a l l the i c e ,  except f o r s c a t t e r e d  and patches which do not c o n s t i t u t e  strings  a hlnderance t o n a v i g a t i o n ,  has melted o r departed from the g u l f .  It  can only be roughly  estimated because the i n f o r m a t i o n a v a i l a b l e w i l l not permit the d e t e r m i n a t i o n of a c t u a l dates  (see Table I I ) .  The  r e l a t i o n s h i p w i t h temperature i s c l o s e r than i n the case o f e i t h e r the p a t t e r n or the r a t e of breakup, but i t  i s not  c l o s e enough to e s t a b l i s h temperature as the main c o n t r o l In t h i s respect. clearing,  19^5,  In s p i t e of the f a c t  that  the year of  earliest  had u n u s u a l l y h i g h temperatures, the y e a r  195  1  was l a t e r i n ^clearing and had even h i g h e r temperatures. However, two of the c o l d e r than average seasons, 1943. and 1950,  were the l a t e s t i n c l e a r i n g .  Low l a t e w i n t e r and e a r l y  s p r i n g temperatures appear to r e t a r d the c l e a r i n g more than low f a l l and e a r l y w i n t e r temperatures. The b e s t c o r r e l a t i o n i s d i s c o v e r e d between the tempera t u r e s of the i c e season and the q u a n t i t y and extent of ice.3^  Due to the l a c k o f r e l i a b l e d a t a concerning w i n t e r  i c e c o n d i t i o n s , t h i s e s t i m a t i o n of the s e v e r i t y  pf each  season i s based p r i m a r i l y on the c o n d i t i o n s e x i s t i n g i n March (see Table I I ) .  The terms used to d e s c r i b e these c o n d i t i o n s ,  " q u a n t i t y " i s meant the t o t a l volume of i c e and by "extent" i s meant the a r e a which i s i c e - c o v e r e d .  79 light,  moderate to l i g h t ,  moderate, moderate to heavy, and i  heavy, are r e l a t i v e o n l y ; each of the t h i r t e e n seasons compared w i t h the r e s t . i c e was l e s s  extensive  The term " l i g h t " i n d i c a t e s that  the  and appeared i n s m a l l e r q u a n t i t i e s  than i n the other y e a r s , while "heavy" i s taken t o a more extensive  is  and abundant occurrence of i c e .  represent The other  terms d e f i n e intermediate c o n d i t i o n s . The seasons of h i g h temperatures c o i n c i d e w i t h those of l i g h t i c e c o n d i t i o n s and the seasons of low temperatures w i t h those of heavy i c e c o n d i t i o n s . the other years f i t  Between these  the p a t t e r n reasonably w e l l .  extremes I t may  appear that lower temperatures i n the l a s t three months cause more severe first  i c e c o n d i t i o n s than lower temperatures i n the  t h r e e , as i s suggested i n the case of 1946  and  195°'  However, the lower temperatures may have r e t a r d e d e a r l y s p r i n g c l e a r i n g which l e d to a misJudgment of the s e v e r i t y ice conditions.  of the  In view of t h i s p o s s i b i l i t y and c o n s i d e r i n g  the nature o f the Information a v a i l a b l e ,  the assumption Is  not J u s t i f i e d . A c c o r d i n g to G. A . Mackay,25 the i c e c l e a r a n c e date i n Hudson Bay i s dependent mainly on the s p r i n g temperatures, and the w i n t e r temperatures have l i t t l e breakup.  i n f l u e n c e on the  T h i s a s s e r t i o n was prompted by h i s  investigations  of a i r temperatures over Hudson Bay, p a r t i c u l a r l y at Churchill.  He was d e a l i n g mainly w i t h l a n d f a s t  sheet Ice and  35Mackay, G. A . , "The E f f e c t of P r o t r a c t e d S p r i n g Thaws on Ice C o n d i t i o n s i n Hudson Bay," B u l l e t i n of the American M e t e o r o l o g i c a l S o c i e t y , 33: 106, March, 195 ' 2  go not w i t h s h i f t i n g pack i c e . Lawrence d i f f e r  from those  A good p o r t i o n of the i c e i s formed, consequently,  C o n d i t i o n s i n the G u l f of i n Hudson Bay i n s e v e r a l  In the  season when  Most o f . t h e  ice  is  s h i f t i n g pack i c e which does not remain i n the  u n t i l temperatures  it  the amount of i c e present may vary  i c e i s forming i n the producing a r e a s .  rather,  respects.  i n the g u l f does not remain where  c o n s i d e r a b l y a c c o r d i n g to the temperatures  constantly  St.  are r a i s e d s u f f i c i e n t l y  i t moves toward Gabot S t r a i t  to melt i t ,  gulf  but  and i s e x p e l l e d t o  the  open A t l a n t i c . Although the breakup of bays and harbours In the may be a c c e l e r a t e d by s p r i n g thaws,  the c l e a r i n g of the  as a whole may or may not respond t o t h i s low s p r i n g temperatures  impetus.  In  gulf gulf  19^3,  may have r e t a r d e d the opening of  Bale de. C h a l e u r , but d i d not a f f e c t  the  the  speedy withdrawal of \  the i c e from the g u l f .  Then i n I 9 5 I and 1952,  temperatures were not s u c c e s s f u l withdrawal. pletely  Is  In b r i n g i n g about  George Bay which g e n e r a l l y subject  to Invasions  i c e sheet has d i s a p p e a r e d .  o f the low s p r i n g temperatures. i n the g u l f were not  freezes  early  over com-  of i c e l o n g a f t e r  In 194-3, however,  c l e a r more than a month before  high spring  its  original  George Bay was  the Bale de C h a l e u r , i n s p i t e , The s m a l l e r bays and harbours  Investigated.  The c o n c l u s i o n i n r e g a r d to. the importance of s p r i n g thaws as a p p l i e d to the c o n d i t i o n s i n the Gulf of Lawrence must be that b r e a k i n g up i c e  t h e i r primary e f f e c t  St.  i s i n decaying and  sheets and i n c o n t r i b u t i n g to the  clearing  process.  As a f a c t o r  i n c l e a r i n g , however,  not predominant o u t s i d e the small h a y s . the w i n t e r temperatures do i n f l u e n c e  s p r i n g thaws are  On the other hand,  the breakup i n that  are p a r t l y r e s p o n s i b l e f o r the q u a n t i t y  they  and extent o f i c e  to  be c l e a r e d away. The a i r temperature i s d e f i n i t e l y importance i n r e s p e c t o f the atmosphere, i c e i n the f i r s t  to i c e c o n d i t i o n s .  of fundamental . It  i n t u r n c o o l i n g the water,  place.  On the average,  i s the  cooling  which produces  mean monthly  a t u r e s are below f r e e z i n g f o r f o u r months o f the y e a r , viding a suitable  climate f o r ice formation.  i s such a v a r i a b l e f a c t o r  differences  are r e f l e c t e d  from those  pro-  A i r temperature  that the temperatures  season may be q u i t e d i f f e r e n t  temper-  o f one  of a n o t h e r .  ice These  p r i m a r i l y i n the amount and the  extent of i c e which e x i s t s i n the g u l f d u r i n g t h a t  season.  When mean monthly temperatures are above average the i c e w i l l be l e s s  abundant and w i l l cover a s m a l l e r a r e a than when  temperatures  are below average.  In s p r i n g the h i g h e r temper-  a t u r e s cause m e l t i n g of i c e and the b r e a k i n g up of l a r g e sheets i n t o pack I c e .  Temperature does not appear,  ice  however,  t o be the most important f a c t o r d e t e r m i n i n g the movements of the i c e ,  the r a t e of w i t h d r a w a l , o r the time of f i n a l Precipitation.  difference  An examination of the f i g u r e s  for  the  from average of the mean monthly p r e c i p i t a t i o n and  the monthly t o t a l of s n o w f a l l i n inches suggests t h a t influence  clearing  the  of p r e c i p i t a t i o n on i c e c o n d i t i o n s In the g u l f  is  82 slight.26  i  n  t h i s i n v e s t i g a t i o n the same s t a t i o n s were used  as i n the case of temperature. The main e f f e c t  of p r e c i p i t a t i o n seems to be the  r e t a r d a t i o n of f r e e z i n g by a snow-cover.  A heavy blanket of  snow l y i n g on the i c e throughout the winter months helps r e t a i n heat. is chiefly  T h i s l i m i t s the t h i c k n e s s o f the i c e because  through conduction of heat upward that the i c e  i s able to b u i l d downward on the under s i d e . when the i c e was heavy, as i n 1943,  1948,  In those  and 1950,  hand, when the i c e was l i g h t e r ,  as i n 1945  and 1946,  other  the The c o r r e -  however.  Whether or not t h i s i n f l u e n c e  i s important,  heavy  s n o w f a l l i s r e s p o n s i b l e f o r the f o r m a t i o n of s l u s h . temperatures f o l l o w a s n o w f a l l the s l u s h f r e q u e n t l y  When low provides  a mortar which a i d s i n cementing pack i c e i n t o l a r g e During the breakup the e f f e c t  sheet  years  On the  tendency was toward h i g h e r than average snowfalls.' l a t i o n i s by no means c l o s e ,  it  the  tendency was toward lower than average s n o w f a l l s .  insignificant.  to  of p r e c i p i t a t i o n i s  sheets.  relatively  Throughout the i c e season, as a whole,  It  is  l i k e l y that p r e c i p i t a t i o n performs a minor r o l e i n determining the i c e c o n d i t i o n s i n the Wind.  gulf.  The wind i s d e f i n i t e l y  the most important  f a c t o r i n determining the d e v i a t i o n from the expected  pattern  and r a t e of withdrawal of the i c e as d i c t a t e d by the n o n 3°Department of T r a n s p o r t , M e t e o r o l o g i c a l D i v i s i o n , Monthly Record (monthly s t a t i s t i c s s e r i e s ) . T o r o n t o , 1940-  1950.  S3 variable factors.  As was i n d i c a t e d by the wind r o s e s  ( f o l l o w i n g page 27),  p r e v a i l i n g winds throughout the w i n t e r  and s p r i n g have a w e s t e r l y  component, but i n s p r i n g t h i s domi-  nance i s l e s s pronounced.  Although the d r i f t of f l o a t i n g  i s approximately t h i r t y degrees direction,  ice  to the r i g h t of the wind  due to the e a r t h ' s r o t a t i o n , i t v a r i e s a c c o r d i n g to  the c l o s e n e s s  of the pack.  In any c a s e ,  i t i s possible  to  d e a l w i t h the e f f e c t  of wind i n the g e n e r a l terms, n o r t h e r l y ,  easterly,  and w e s t e r l y without  southerly,  directions.  specifying  There i s no doubt t h a t westerly  potent f a c t o r ,  actual  winds are a  combining w i t h the c u r r e n t s , i n c a u s i n g the  t o move toward Cabot  Strait.  In o r d e r to d i s c o v e r the i n f l u e n c e on the i c e of annual v a r i a t i o n of the wind, the s t a t i s t i c s  f o r the  mileage of wind by d i r e c t i o n s were examined at s t a t i o n s . 37  These f i g u r e s  total  i n d i c a t e the p r e v a i l i n g d i r e c t i o n  wind, r a t h e r , than by the t o t a l hours of wind.  of  the  In a d d i t i o n ,  s y n o p t i c charts f o r the months of March and A p r i l were  scanned i n the case of the years 1944, 1952.  the  twelve  f o r each month as determined by the t o t a l v e l o c i t y  daily  ice  These o b s e r v a t i o n s proved t h a t  1945,  1945,  1951,  and  the winds d u r i n g  F e b r u a r y , March, and A p r i l are the primary c o n t r o l of  the  p a t t e r n and r a t e of breakup, as w e l l as of the time of f i n a l clearing. A short p e r i o d of s t r o n g wind from one d i r e c t i o n tends t o have a g r e a t e r e f f e c t 5 Ibld.. 7  on i c e movement than a l o n g p e r i o d  1940-1950.  o f weak wind. the f o r c e s  This i s l o g i c a l because  of f r i c t i o n before  the wind must overcome  the i c e can be moved a p p r e c i a b l y .  T h e r e f o r e , g a l e s exert an i n f l u e n c e q u i t e out of p r o p o r t i o n to the l e n g t h of time they blow.  Strong winds are a b l e to  power water c u r r e n t s i n some i n s t a n c e s .  Only the  over-  constant  c u r r e n t s i n the g u l f are never checked by the wind; the weak flows  and the t i d a l c u r r e n t s are a l l s u s c e p t i b l e  of wind, e s p e c i a l l y  when l o o s e i c e i s p r e s e n t .  p r e s e n t the wind with a rougher s u r f a c e that  to the power The i c e  i s easier to g r i p .  Not only does the wind a i d o r hamper the normal water flow,  but a l s o  i t generates  flow even a f t e r  floes  current  c u r r e n t s which may continue  the wind has  In view of the great  to  abated. t r a n s p o r t i n g power of wind,  i s obvious t h a t a p e r i o d of s e v e r a l days w i t h s u s t a i n e d wind from one d i r e c t i o n can r e d i s t r i b u t e tremendous ties  of pack i c e i n the g u l f .  The frequency  it strong  quanti-  of such p e r i o d s  of wind from the same d i r e c t i o n d u r i n g F e b r u a r y , March, and A p r i l i s of utmost importance.  F o r e x a m p l e , . i n 1952,  strong  n o r t h e r l y winds p r e v a i l e d f o r s e v e r a l p e r i o d s of a week o r more i n February and March, r e s u l t i n g i n accumulation of  the  i c e i n the southern p a r t of the g u l f  &9).  The same p r o c e s s o c c u r r e d i n 1951, more e a s t e r l y  (see Table I I ,  except that  page  the winds were  and continued u n t i l the middle of A p r i l ,  the lee toward the western s e c t i o n .  In 1943,  driving  sustained  s o u t h e r l y winds were r e s p o n s i b l e f o r pushing the i c e northward where i t found i t s way out of the g u l f  readily.  These cases are extreme; the more l i k e l y  occurrence  i s the c a n c e l l i n g of the work of one p e r i o d by t h a t of a n o t h e r . That i s to say, days,  i f the winds are s t r o n g e a s t e r l y  they may be s t r o n g westerly  f o r a few  i n the next p e r i o d .  Often  the p e r i o d s are short and cause only minor d i v e r s i o n s o f the ice.  A p e r i o d of very l i g h t v a r i a b l e winds may c r e a t e  s t a g n a t i o n of the i c e as o c c u r r e d i n l a t e A p r i l , These i n f l u e n c e s  1952.  of the wind are r e f l e c t e d ,  been p o i n t e d o u t , i n the p a t t e r n of breakup.  a  as has  Those years  which the i c e tended to stagnate i n the southern p a r t of  in the  g u l f were c h a r a c t e r i z e d by e x c e s s i v e s t r o n g n o r t h e r l y wind at some time d u r i n g the season or l a c k of s u f f i c i e n t wind.  In some cases there was an a c t u a l accumulation of  i n the s o u t h , as i n 1 9 5 , 2  while i n others the i c e  simply d i d not withdraw r e a d i l y , as i n 19^4. 1952  southerly ice  present  The season of  serves as an example of s t a g n a t i o n throughout A p r i l due  t o weak and v a r i a b l e winds as w e l l as one of southern . accumulation. On the o t h e r hand, the years  i n which the i c e withdrew  more r e a d i l y from west to east experienced a f a v o u r a b l e combination o f wind throughout the s p r i n g season.  Short  p e r i o d s of s o u t h e r l y winds f o l l o w e d by l o n g e r p e r i o d s of westerly south.  appear to assure the withdrawal of the i c e from the If  s t r o n g winds occur f r e q u e n t l y ,  exodus i s a c c e l e r a t e d .  as In 19^5*  The other p a t t e r n s ,  the i c e moved northward d u r i n g A p r i l ,  the  t h a t of 19^3,  and that of 1 9 5 , 1  when  when  the i c e l i n g e r e d i n the western p a r t of the g u l f , were caused by s o u t h e r l y and e a s t e r l y winds  respectively.  &6 The i n f l u e n c e apparent because  of the wind on the r a t e of breakup  is  the wind i s a v i t a l f a c t o r i n moving the  ice..  Should the wind combine f o r c e s w i t h the water c u r r e n t s i n d r i v i n g i c e through Gabot S t r a i t and i n feeding w i t h i c e from the bays and b i g h t s of the g u l f , contrary,  this.stream  of the more c o n f i n e d  the c l e a r i n g would p r o g r e s s r a p i d l y .  sections  But on the  should the wind oppose the water c u r r e n t s and other  f o r c e s t e n d i n g t o c l e a r the g u l f , retarded.  T h i s adverse  effect  the c l e a r i n g would be  occurs most s e v e r e l y  with n o r t h -  east winds which, c o n s i d e r i n g the d e v i a t i o n i n the d r i f t the i c e ,  d r i v e the i c e southward.  to t h i s e f f e c t .  Of c o u r s e ,  The case of 1952  the r a t e  is  of  witness  of breakup may be r a p i d  through p a r t of the season and then be slowed by n o r t h e r l y o r easterly  winds f o r a short p e r i o d of t i m e .  was subject  The season of l$k-&  to n o r t h and northeast winds of a h i g h  velocity  toward the end of A p r i l which f o r c e d the i c e onshore along the east coast  of Cape B r e t o n , although i t had been  offshore  throughout most of the month. S i m i l a r l y , the time of f i n a l c l e a r i n g i s mainly determined by the wind. c a u s i n g s t a g n a t i o n i n the directly  In r e t a r d i n g the withdrawal of i c e by southern s e c t i o n ,  the wind i s  r e s p o n s i b l e f o r i c e remaining unduly l a t e  In s e v e r a l  i n the  i n s t a n c e s when there was a d i r e c t w i t h d r a w a l ,  i c e was h e l d onshore i n the d i s p e r s a l r e g i o n by e a s t e r l y The quantity the wind.  and extent of i c e are a l s o a f f e c t e d  gulf. the winds. by  When i c e f o r m a t i o n i s i n p r o g r e s s the wind a i d s  the t i d e s and t i d a l c u r r e n t s i n disengaging  i c e from the l a n d  87 and from shoals i n the producing areas and c a r r y i n g i t away t o add to the  s h i f t i n g pack.  The extent of i c e may he reduced  m a t e r i a l l y by accumulation i n one p a r t i c u l a r a r e a as a r e s u l t o f wind.  In t h i s manner the wind i s o f t e n r e s p o n s i b l e f o r  closeness  of pack  ice.  Most of the s h i f t i n g i n p o s i t i o n of pack Ice d i r e c t l y by the wind.  N o r t h e r l y winds brought i c e  is  In 1948,  of  s o u t h e r l y winds pushed the i c e to  n o r t h side of Northumberland S t r a i t and kept the i c e o f f  caused  southward  b l o c k i n g the steamer t r a c k i n m i d - A p r i l i n the seasons 1942 and I95O.  about the middle of  the Gape Breton east c o a s t .  the other around A p r i l 25.  Likewise,  Westerly winds g e n e r a l l y  c o a s t a l areas r e a d i l y .  The northward movement of i c e i n  o c c a s i o n e d by s o u t h e r l y winds, e f f e c t i v e l y of the Bale de Chaleur which g r e a t l y  i c e from the g u l f .  clear  southeast  c o a s t s of P r i n c e Edward I s l a n d , the Magdalen I s l a n d s ,  The wind i s of.utmost  to  T h i s e f f e c t may be n o t i c e d  along the n o r t h side of the Bale de C h a l e u r , the  Cape Breton I s l a n d .  the  April  i n I952, the i c e was s h i f t e d from one s i d e of the s t r a i t  southeast  the  19^3>  b l o c k e d the mouth  retarded i t s  Importance  and  clearing.  i n the c l e a r i n g of  On the average, the p r e v a i l i n g  westerly  winds d u r i n g the i c e season assure t h a t most of the i c e w i l l eventually  depart from the g u l f through Cabot S t r a i t .  l o s s of dominance by w e s t e r l y time r e s u l t s  in a different  winds f o r v a r y i n g p e r i o d s of  behaviour of the i c e .  sustained northerly or easterly ice  The  Periods of  winds cause accumulation of  i n the southern p a r t of the g u l f  and slow the r a t e of  .  SABLE I I  BJSLAIIONSHIPS BETWEEN TEMPEHATOEE, WIND, AND ICE CONDITIONS  Group  Year  Temperatures  Winds  Time of F i n a l Clearing  Quantity and Extent of Ice  rapid i n March and i p r i l  early i p r i l  light  A.  slow i n March 'and i p r i l  late i p r i l  light  rapid i n March and .April  late April  moderate to l i g h t  slow i n March and A p r i l  early May  moderate to l i g h t  west to east, direct withdrawal  moderate i n March, rapid i n i p r i l  early May  moderate to l i g h t  stagnation In south  moderate i n March, slow i n i p r l l  early May  moderate to l i g h t  early May  moderate  (. .  1. above average temperatures  B.:  (  c. -  2. f i r s t 3 mouths colder than last 3  most months well above average most months above average or near average  west to east, d i r e c t withdrawal  19^5  strong westerly  195I  strong easterly and northerly  1949  northerly and westerly  west to east, d i r e c t withdrawal  1952  strong northerly and l i g h t , variable  stagnation i n south  19*40  1942  f i r s t three months near average, l a s t three months higher than average  A.  Bate of Breakup  Pattern of Breakup  •j  every month well above average  1946  (insufficient  data)"  strong northerly strong westerly followed by northerly and easterly  gg  west side accumulation  stagnation i n south  . . . . . . . . . . . . . . . .  r a p i d i n March slow i n i p r l l  -  west to east, direct withdrawal  r a p i d i n March and i p r l l  late i p r i l  moderate to heavy  westerly and southerly  west to east, direct withdrawal  rapid i n March and i p r l l  early May  moderate to heavy  l9*+g  strong westerly followed by strong northerly and easterly  west toceast, direct withdrawal  1950  strong northerly  stagnation i n south  moderate i n March slow i n i p r i l  Two of f i r s t three months above average 19I& l a s t three below average  strong westerly and northerly  stagnation i n south  rapid i n March slow i n i p r i l  late i p r i l ;  south to north, d i r e c t withdrawal  rapid i n March and i p r i l  early May  f i r s t three months / 1 9 l lower than average; l a s t three higher than average 1947 u  ;  B.:  (insufficient  data)  -  i  A . ;  f i r s t three months above average, l a s t three months below, average  3. f i r s t 3 months warmer than last 3 k "below average temperatures  B.J  four months well below average  1943  strong southerly and westerly  r a p i d i n March and i p r i l  middle of May  heavy  middle of May  heavy moderate to heavy  heavy  clearing.  Westerly and s o u t h e r l y winds i n combination l e a d  to the prompt withdrawal of i c e through Gabot S t r a i t . r e s u l t , wind i s the major f a c t o r i n / d e t e r m i n i n g the  As a  pattern  and r a t e of breakup as w e l l as the time of f i n a l c l e a r i n g , and it  i s r e s p o n s i b l e f o r many of the minor changes  the pack  i n position of  ice. SUMMARY The process of i c e formation and m e l t i n g i s  caused by temperature. water temperatures,  directly  Because d a t a i s l a c k i n g concerning  only a i r temperatures  o f the i n f l u e n c e of t h i s  factor.  are used as an Index  The f a c t  that  the  temper-  a t u r e s do become low enough i n w i n t e r to cause formation of i c e and h i g h enough i n s p r i n g to cause m e l t i n g temperature ditions.  as the primary f a c t o r i n determining i c e  Beyond the bounds of average c o n d i t i o n s ,  v a r i a t i o n s of temperature l a r g e l y  clearing.  t o o r i g i n a t e and i t  open ocean.  annual and  final formation,  Induces  ioe  i s the p h y s i o g r a p h i c framework which Is movement of i c e to  The bays and b i g h t s d e t a i n the i c e and  islands constitute  obstacles  In the p a t h of  Assuming the e x i s t e n c e the f a c t o r s  to i c e  of some areas that  r e s p o n s i b l e f o r o b s t r u c t i n g the f r e e  effective  the time o f  With the temperature f a v o u r a b l e  i s p a r t l y the shallowness  con-  determine the q u a n t i t y  extent of i c e and to a c e r t a i n degree  it  establishes  of movement e x e r t  i n breaking i c e  the  offshore  movement.  of i c e w i t h i n t h i s their influence.  framework,  The t i d e s  are  sheets which have formed along the  shore o r - o v e r shoals and winds and t i d a l c u r r e n t s keep the i c e i n motion i n many s e c t i o n s winter.  of the g u l f throughout  In t h i s manner the t o t a l i c e  supply i s  the  augmented.  Constant ocean c u r r e n t s p r o v i d e a system of t r a n s p o r t a t i o n which c a r r i e s i c e i n t o the g u l f from the S t . Lawrence and a l s o conducts i c e o u t s i d e through Cabot S t r a i t . of constant  The l a c k  c u r r e n t s i n the southern p a r t of the g u l f to a i d  i n the removal of i c e i s p a r t l y r e s p o n s i b l e f o r the n a t i o n s which f r e q u e n t l y  remarkable v a r i e t y  of movement cannot e x p l a i n  of behaviour p a t t e r n s  mental i n causing these v a r i a t i o n s t o be the predominant f a c t o r  c l e a r i n g and the q u a n t i t y  is  It  appears  the time of  final  The c o n t i n u a l  of pack i c e i n r e l a t i o n to the l a n d i s  the  Instru-  i n d e t e r m i n i n g the p a t t e r n and  and extent of i c e .  due to the w i n d ' s I n f l u e n c e .  the  of the i c e .  i s the wind.  r a t e of breakup and, to a c e r t a i n degree,  f a c t o r s which i n f l u e n c e  stag-  occur In t h a t a r e a .  But these f a c t o r s  fluctuation  estuary  essentially  While there are numerous other i c e d u r i n g the breakup season,  suggested t h a t these are the major  ones.  it -  CHAPTER VI CONCLUSION The I n v e s t i g a t i o n G u l f of S t . the f a c t  Lawrence d u r i n g t h i r t e e n breakup seasons  that  although i t  of the d i s t r i b u t i o n of i c e i n the  the behaviour of the i c e i s extremely  follows  mental f a c t o r s  yields  certain patterns.  which exert  variable,  Examination of e n v i r o n -  an i n f l u e n c e on the i c e  reveals  distinct  c o r r e l a t i o n s w i t h the behaviour of the i c e .  These  factors,  both n o n - v a r i a b l e and v a r i a b l e i n f u n c t i o n , act  in  combination to determine the i c e b e h a v i o u r , but i t  Is  variable factors,  chiefly  mainly m e t e o r o l o g i c a l ,  r e s p o n s i b l e f o r the year to year  which are  the  differences.  In view of the v a r i a b l e behaviour of the i c e due to these f a c t o r s ,  the d e t e r m i n a t i o n of average c o n d i t i o n s  rendered d i f f i c u l t .  The t h i r t e e n - y e a r p e r i o d examined i s  h a r d l y l o n g enough to achieve v a l i d averages. that many of these years were d i s t i n c t l y respect fact  to temperature,  serves  to I n d i c a t e  as a whole, were l e s s i n a future p e r i o d . can be made w i t h  It  is  established  above average i n  while few were below average. t h a t the i c e  severe  This  c o n d i t i o n s of t h i s  than those which might be  Nevertheless,  certain  period, expected  generalizations  justification.  The Gulf of S t . covered;  is  Lawrence i s never completely  Ice-  there are always areas o f open water because much of  the i c e i s s h i f t i n g pack i c e ,  especially  i n the  central.part.  The southern s e c t i o n Is an area of accumulation and there  are  usually large  Ice sheets i n t h i s r e g i o n as w e l l as  a b l e c l o s e pack i c e .  consider-  In most p a r t s o f the g u l f the i c e  not remain i n the s p r i n g u n t i l I t m e l t s ,  does  but r a t h e r , i t  i n t o the open A t l a n t i c p r i m a r i l y through Cabot  drifts  Strait.  The discharge of i c e i s commonly i n p r o g r e s s d u r i n g F e b r u a r y , but i t i s a c c e l e r a t e d seldom completely  i n March.  Cabot S t r a i t  b l o c k e d f o r more than a few days at a t i m e ,  In s p i t e of the statement  which appears i n the G-ulf of  Lawrence P l l o t ^ to the e f f e c t i c e n e a r l y every y e a r ,  that  it  5& degrees  Occasionally,  St.  i s blocked s o l i d with  o f t e n f o r t h r e e weeks at a t i m e .  i c e f i e l d i n the d i s p e r s a l r e g i o n g e n e r a l l y past  is  extends  west and southward past 45 degrees  The  eastward north.  the i c e moves onshore along the south coast  Cape Breton under the i n f l u e n c e of e a s t e r l y encroaches on the a r e a o f f  the south coast  Most of the' i c e which i s the f i r s t  of  winds, but seldom of Newfoundland.  to depart from the  gulf  comes from the c e n t r a l a r e a between A n t i c o s t l I s l a n d and Gabot S t r a i t .  However, t h i s c e n t r a l r e g i o n may continue  be i c e - c o v e r e d u n t i l l a t e Invasions  to  i n March o r e a r l y i n A p r i l due to  of i c e from o t h e r  areas.  Most of the i c e i n the lower estuary  of the  St.  Lawrence R i v e r f i n d s i t s way i n t o the g u l f by the middle of March, l e a v i n g the s t r e t c h between P o i n t e des Monts and the gulf  c l e a r of i c e .  Toward the end of March the  opens and allows n a v i g a t i o n to commence.  steamer  Frequently,  route  the  passage n o r t h of - A n t i c o s t l I s l a n d c l e a r s before t h a t  south  Department of Mines and Resources, G u l f of Lawrence P i l o t , T h i r d E d i t i o n . Ottawa, 1946, p . L .  St.  ?  of i t .  The steamer t r a c k i s sometimes b l o c k e d by i c e d u r i n g  A p r i l when n o r t h e r l y winds d r i v e i c e from the n o r t h e a s t arm across i t . Cape S t .  O r d i n a r i l y , however,  the i c e n o r t h of a l i n e from  George to Natashquan i s not d i s c h a r g e d through Cabot  S t r a i t but tends to d r i f t northward where i t  disintegrates  and m e l t s . Early  i n A p r i l the i c e withdraws from the  p a r t of the g u l f ,  western  l e a v i n g i c e i n the Baie de C h a l e u r ,  the bay i s c l e a r i n g a l o n g the n o r t h e r n s i d e .  although  Throughout  the  southern s e c t i o n the l a r g e r i c e sheets are b r e a k i n g up, r e n d e r i n g the i c e more m o b i l e . of i c e through Cabot S t r a i t  In the meantime,  the  stream  continues w i t h the b u l k of  c o n f i n e d to the Cape B r e t o n s i d e .  ice  The f i e l d of i c e beyond the  s t r a i t has receded from i t s p o s i t i o n of g r e a t e s t extent i n March.  As the month progresses  Strait.  the i c e moves toward Cabot  The r e g i o n around the Magdalen Islands c l e a r s  the southern area and the b e l t of Ice narrower.  In Cabot S t r a i t  Ice that  c l e a r s from i t s western entrance  to withdraw from the g u l f i n the southeastern  Breton. but i t  becomes  Most of the i c e has departed from the Baie de  Chaleur by the end of the t h i r d week i n A p r i l . Strait  before  In l a t e  Northumberland  eastward and the  last  A p r i l o r e a r l y May Is  s e c t o r a l o n g the west coast  of Cape  Sometimes the S t r a i t of Canso c l e a r s i n e a r l y  April,  i s dependent on the c l e a r i n g of George Bay and the  may remain here u n t i l the end of the month.  Likewise,  found i n the d i s p e r s a l r e g i o n o f f the Cape Breton east u n t i l the end of  April.  ice  Ice is  coast  The i c e f i e l d s  are c o n s t a n t l y  Some areas may be c l e a r at others,  shifting  position.  c e r t a i n times and i c e - c o v e r e d  at  depending p r i m a r i l y on the d i r e c t i o n of the wind.  Such f l u c t u a t i o n s  are e s p e c i a l l y  noticeable  along the east and  south c o a s t s of Cape Breton where the i c e may be d r i v e n alternately  onshore and offshore  these encroachments, f o r a few days  As a r e s u l t  L o u i s b u r g harbour i s sometimes  in April,  l e a d i n s i d e the  by the wind.  but u s u a l l y  ice f i e l d .  t o these i n v a s i o n s because  of  blocked  there e x i s t s a shore  The east coast  i s more  susceptible  the i c e does not c l e a r from t h i s  a r e a u n t i l the end of A p r i l or e a r l y May.  Consequently,  Sydney harbour may be b l o c k e d f o r l o n g e r p e r i o d s and u n t i l  a  l a t e r date than L o u i s b u r g . The v a r i a b i l i t y of the i c e  c o n d i t i o n s i n the breakup  season i s w e l l i l l u s t r a t e d by the t h i r t e e n years With the g u l f 1945  essentially  open by the end of March, the  probably witnessed one of the e a r l i e s t  might be expected.  but I t  equally d i s t i n c t i v e ,  it  appears t h a t ,  i s possible  that  occur.  that  and 195 other  1  saw i c e  m  ay  gulf  n  most o f t e n ,  of the t h i r t e e n  the i c e w i l l e i t h e r  years  years  withdraw Strait  or w i l l tend to stagnate i n the southern p a r t of  toward the end o f the  season.  ^t  patterns,  d i r e c t l y from the west to e a s t , p a s s i n g through Cabot readily,  of  are not r e p r e s e n t e d among the  On the b a s i s  year  which  The unusual p a t t e r n s  breakup which c h a r a c t e r i z e d the years 1943  s t u d i e d may yet  clearings  On the other hand, the year 1950  remain i n the g u l f u n t i l May 15.  occur frequently,  examined.  the  BIBLIOGRAPHY BOOKS Atwood, W. W., The P h y s i o g r a p h i c P r o v i n c e s o f North America, Boston: Ginn and Company, 19^0 " 536 pp. B a r n e s , Howard T . , Ice E n g i n e e r i n g . M o n t r e a l : Renouf P u b l i s h i n g C o . , 1928. 364 p p . Johnson, Douglas W., The New England-Acadian S h o r e l i n e . New Y o r k : John Wiley and Sons, I925. 60S p p . Johnson, Douglas W., Shore Processes and S h o r e l i n e Development. New Y o r k : John Wiley and Sons, I n c . ,  I9I9.  Koeppe, Clarance Eugene, The Canadian C l i m a t e . Bloomlngton, I l l i n o i s : McKnight and McKnlght, 1931. 280 pp. Shepard, F r a n c i s P . , Submarine Geology. and B r o t h e r s , 1948. 348 pp. Stewart, John Q., Coasts. and Company, 1945.  New Y o r k : Harper  Waves and Weather. 348 pp.  Boston: Ginn  Sverdrup, H . U . , M. W. Johnson, and R. H . F l e m i n g . The Oceans. New York: P r e n t i c e - H a l l , 1946. 1,087 pp. Taylor, G r i f f i t h , 524 pp.  Canada.  London: Methuen and C o . ,  1947.  PERIODICALS B a r n e s , H . T . , "St. Lawrence and I t s Ice Problems," Canadian E n g i n e e r . 57:738-39, November 19, 1929. B a r n e s , H . T . , "Ice Formation on the S t . Lawrence," Canadian E n g i n e e r . 20:789-92, June 8, 1911. Bencker, L i e u t .-Commander H . , "Ice Terminology," The Hydrographic Review, 8:114-31, November, 1931. Boughner, C. C , "The Climate of Canada," Q u a r t e r l y J o u r n a l of the Royal M e t e o r o l o g i c a l S o c i e t y . 63:419-31.  jTriyT^L^TT"  Gordon, A . R . , and W. C. Woodworth, "Some I n t e r - R e l a t i o n s h i p s of Snow and Ice C o n d i t i o n s and Weather i n the A r c t i c , " B u l l e t i n o f the American M e t e o r o l o g i c a l S o c i e t y , 31:271-7s7~0cTober, I956. Hachey, H . B . , "Surface Water Temperatures o f the Canadian A t l a n t i c C o a s t , J o u r n a l o f the F i s h e r i e s Board- of Oanada, 4 : 3 7 6 - § l , February, 1940. 0  H a r e , F . Kenneth, "The Climate o f the I s l a n d of Newfoundland: A Geographical A n a l y s i s , " Geographical B u l l e t i n , 2:36-88, 1952. H a r e , F . K . , and M. R. Montgomery, " I c e , Open Water, and Winter Climate i n the E a s t e r n A r c t i c of North A m e r i c a , " P a r t s 1 and 2, A r c t i c . 2:79-89, 14-9-64, September and December, 1 9 4 § . K e r r y , J . G . G . , "Winter N a v i g a t i o n on the S t . Lawrence," The Dock and Harbour A u t h o r i t y . 31:220-225, November, K e r r y , J . G . G . , "The S t . Lawrence Waterway, an A l l - C a n a d i a n and Very Deep R o u t e , " The E n g i n e e r i n g J o u r n a l , 34:536-43, June, 1951. . K e r r y , J . G . G . , "Ice Blockade o f Canadian P o r t s , " The Dock and Harbour A u t h o r i t y , 27:273-76, March, 19^7? K e r r y , J . G . G . , "The S t . Lawrence Waterway," ( d i s c u s s i o n of the paper, "The S t . Lawrenee Waterway, An A l l Canadian and Very Deep R o u t e " ) , The E n g i n e e r i n g J o u r n a l . 34:957-65, October, 1951. Mackay, G. A . , "The E f f e c t o f P r o t r a c t e d Spring Thaws on Ice C o n d i t i o n s i n Hudson B a y , " B u l l e t i n o f the American M e t e o r o l o g i c a l S o c i e t y , 33:101-O"o". March. 1952. Putnam, D. F . , "Climate o f the Maritime P r o v i n c e s , " Canadian Geographical J o u r n a l , 21:135-47, September, 1940. "Sea I c e : Terminology, Formation and Movement," The P o l a r Record, 4:126-33, January, 1944. Smith, E . H . , "Some M e t e o r o l o g i c a l Aspects of the Ice P a t r o l Work i n the North A t l a n t i c , " Monthly Weather Review, 50:629-31, December, 1922. "Symposium, Canada's Oceans—Known and Unknown," Proceedings of the Royal Society o f Canada, 4-3:153-90, June, 1949.  97  GOVERNMENT PUBLICATIONS Dawson, W. B e l l , The T i d e s and T i d a l Streams With I l l u s t r a t i v e Examples From Canadian Waters. Ottawa: Department o f the Naval S e r v i c e , 1920" 4"3"~pp. Department of Marine and F i s h e r i e s , The Currents on the Southeastern Coasts o f Newfoundland. Ottawa, I906. Department o f Marine and F i s h e r i e s , The Currents i n B e l l e Isle Strait. Ottawa, I907. Department o f Mines and Resources, G u l f o f S t . Lawrence P i l o t . T h i r d E d i t i o n . Ottawa, 19457 376 p p . Department of Mines and Resources, Hydrographic S e r v i c e , "General Correspondence on Ice C o n d i t i o n s , " F i l e No. 634, v o l . 3. Ottawa, I 9 2 2 - I 9 5 I . Department o f Mines and Resources, Hydrographic S e r v i c e , " D a i l y Ice R e p o r t s , " F i l e No. 634, v o l . 2. Ottawa, 1941-1951. Department o f Mines and Resources, Hydrographic S e r v i c e , " Q u e s t i o n n a i r e , Re: Ice C o n d i t i o n s i n the G u l f of S t . Lawrence," F i l e No. 634, v o l . 1. Ottawa, 1937. Department of Mines and T e c h n i c a l Surveys, Tide Tables f o r the A t l a n t i c Coast o f Canada, a l s o Current t a b l e s and Information on C u r r e n t s . Ottawa, 1952. T2b p p . Department o f Mines and T e c h n i c a l Surveys, Tide L e v e l s and T i d a l Bench Marks. Ottawa, 1951. 88 p p . Department o f Mines and T e c h n i c a l Surveys, Geographical Branch, "Canadian Ice D i s t r i b u t i o n Survey F i l e , " Ottawa, 1951. Department o f the Naval S e r v i c e , The Currents i n the G u l f of S t . Lawrence. Ottawa, 1913. 4b pp. Department o f the Naval S e r v i c e , The Currents i n the Entrance to the S t . Lawrence. Ottawa, 1913* 5 PP' Q  Department o f the Naval S e r v i c e , Temperatures and D e n s i t i e s of the Waters o f E a s t e r n Canada. Ottawa, 192~eT 102 p p . Department o f Trade and Commerce, Dominion Bureau o f S t a t i s t i c s , "The Climate o f Canada. Part I I , " The Canada Year Book 1950. Ottawa, 1950. pp.V^3^.70.  Department o f Trade and Commerce, Dominion Bureau of S t a t i s t i c s , "The Climate of Canada, Part I , " The Canada Year Book 1943-49. Ottawa, 194-9. pp.TT-63. Department d f T r a n s p o r t , "Ice Report o f G . G . S . F i l e No. 3262-3, v o l . 1. Ottawa, 1940.  Gltadelle,"  Department of T r a n s p o r t , "Ice Report of C.G-.S. N. B . M a c l e a n , " F i l e No. 8262-3, v o l . 1. Ottawa, 1940. Department of T r a n s p o r t , "Reports o f A e r i a l Ice Surveys i n the G u l f of S t . Lawrence," F i l e No. 8262-3, 8 v o l s . Ottawa, 1940-1952. Department o f T r a n s p o r t , M e t e o r o l o g i c a l D i v i s i o n , C l i m a t i c Summaries f o r S e l e c t e d M e t e o r o l o g i c a l S t a t i o n s i n the Dominion of Canada, 2 v o l e . Ottawa. 1948. Department of T r a n s p o r t , M e t e o r o l o g i c a l D i v i s i o n , Monthly Record (monthly s t a t i s t i c s s e r i e s ) . Toronto, I940-I950. Department o f T r a n s p o r t , M e t e o r o l o g i c a l D i v i s i o n , Monthly Weather Map (monthly weather map s t a t i s t i c s s e r i e s ) . Toronto,"T951-1952. O u t s e l l , B. V . , An I n t r o d u c t i o n t o , t h e Geography of Newfoundland, Information S e r i e s No. 1. Ottawa: Department o f Mines and Resources, Geographical Bureau,  1949.: 85 pp.  Huntsman, A . G . , A r c t i c Ice On Our E a s t e r n Coast, B u l l e t i n No. 13, B i o l o g i c a l Board of Canada. T o r o n t o , January, 1930. Jones, I , W., "An O u t l i n e o f the Geology of the P r o v i n c e of Quebec," P r o v i n c e of Quebec S t a t i s t i c a l Yearbook 1947. Quebec: Government of Quebec, 19^7* PP. K r i e g s m a r i n e , Ubootshandbuch der Ostkdste Kanadas B e r l i n , xTpBT. pp. 166,"TfO"  (Atlas).  Sandstrdm, J . W., "The Hydrodynamics o f Canadian A t l a n t i c Waters," Canadian F i s h e r i e s E x p e d i t i o n , 1914-1915. Ottawa, I919. PP. 221-91. S m i t h , F . C . G . , "Hydrographical F e a t u r e s , " Canada Year Book 1947. Ottawa: Department of Trade and Commerce, Dominion Bureau of S t a t i s t i c s , 1947. p p . 3-12.  S o u l e , F l o y d M . , and E . R. C h a l l e n d e r , " D i s c u s s i o n of Some of the E f f e c t s of Winds on Ice D i s t r i b u t i o n i n the V i c i n i t y of the Grand Banks and the Labrador S h e l f , I n t e r n a t i o n a l Ice Observation and Ice P a t r o l S e r v i c e In the North A t l a n t i c Ocean, Season of 1947. Washington: U. S. Treasury Department, Coast Guard, 19^9. PP..59-61. 8  U . S. Navy, Hydrographic O f f i c e , Ice A t l a s o f the Northern Hemisphere, F i r s t E d i t i o n . Washington, 1946T U . S. Navy, Hydrographic O f f i c e , World A t l a s of Sea Temperatures. Washington, 194-8.  Surface  U . S. Navy, Hydrographie O f f i c e , "A F u n c t i o n a l Glossary of Ice Terminology," Study No. 103, P r o v i s i o n a l , May, 1948. U . S. Treasury Department, Coast Guard, I n t e r n a t i o n a l lee Observation and l e g P a t r o l S e r v i c e i n the North A t l a n t i c " S c e a n , B u l l e t i n s 3 1 , 3 2 . 357 34, and 35. (Seasons 1941 to 1949, i n c l u s i v e ) . Washington, 1941-1949.  \  —- J„.,'  APPENDIX '\, 'MAPS OF 'LIMITS OF MAIN ICE AREAS  9 10 11 12 13 14 15  Season Season Season Season Season Season Season > 16 Season 17 Season 18 Season 19 Season 20 Season 21/'Season 1  '  '  o f 1940 o f 1941 o f 1942 o f 1943 o f 1944 o f 1945 of, 1946 o f I947 o f 1948 o f 1§49 o f 1950 o f I95I o f 1952  '  64  GULF OF ST. LAWRENCE LIMITS  OF MAIN  BREAKUP  SEASON Ice  .  50  ICE  April  5 fh  April  IS fh  AREAS  OF 1 9 4 0  Limits  April 25 th  MEAN  MONTHLY  TEMPERATURE  DIFFERENCE  FROM  AVERAGE  (EOC  > N  o\ 2  41 6  S  NOV  1939  DEC  1939  66  J A N  1940  F E B  1 9 4 0  M A R  1940  A P R  1940  GULF LIMITS  OF  OF M A I N  BREAKUP  N O V .  19 4 0  ST.  LAWRENCE ICE  SEASON  AREAS  O F 1941  D E C  1 9 4 0  J A N  1 9 4 1  F E B  1 9 4 1  M A R  1 9 4 1  A P R  1 9 4 1  GULF LIMITS  OF ST. L A W R E N C E OF  BREAKUP  MEAN  MAIN  ICE  AREAS  S E A S O N OF 1 9 4 3  MONTHLY  TEMPERATURE  DIFFERENCE  FROM  AVERAGE  •Ol  10 N O V  19 4 2  D E C  1 9 4 2  J A N  1 9 4 3  F E B  1 9 4 3  M A R  1 9 4 3  A P R  1 9 4 3  -14  Sable  Isiond  GULF  OF ST. L A W R E N C E  LIMITS  OF MAIN  BREAKUP  ICE  AREAS  S E A S O N OF 1 9 4 4  BESMB  Apr.i  5 tn  BH9  April  5 ' i  66  GULF  60  OF ST. L A W R E N C E  LIMITS  OF  MAIN  BREAKUP  5  0  E  U  B  E  C  AREAS  S E A S O N OF Ice  A p n l  ICE  58  1945  L i m i t s  f h  M a y  I S t  April  IS t h  May  5 f h  April  2 5 f h  NO  Open  A o t e r  SC»L£  IN  A p n I  DATA  5 f h  MliES  H 46  MEAN  MONTHLY  TEMPERATURE  DIFFERENCE  FROM  AVERAGE  (Each  d o t  represen-s  one  station)  's  44  M  44  So ble island  N O V  1 9 4 4  DEC  1944  J A N  1945  FEB  1945  M A R .  1 9 4 5  A P R  1 9 4 5  62  60  58  66  GULF LIMITS  OF S T  LAWRENCE  O F MAIN  BREAKUP  ICE  AREAS  S E A S O N OF 1 9 4 8  50K-  4fcr~  MEAN  MONTHLY  TEMPERATURE  DIFFERENCE  FROM  AVERAGE  (tad  ~ n b'o'io  J C'  e  HiOl  8 4  Sctle  islcrd  6 8 10 N O V  1 9 4 7  DEC  19 4 7  J A N  1 9 4 8  F E B  19 4 8  M A R  1 9 4 8  A P R  1 9 4 8  12 14 60  58  GULF  OF  ST.  LAWRENCE  LIMITS OF MAIN ICE AREAS BREAKUP SEASON OF 1 9 4 - 9  50  H  46  VEAN  MONTHLY  T  EMPERATURE  DIFFERENCE  FROM  AVERAGE  Ssfcie  N O V  1 9 4 8  D E C  1 9 4 8  be  J A N  1949  F E B  1949  M A R  1 9 4 9  A P R  . 1 9 4 9  isle  66  GULF  OF ST. L A W R E N C E Q OF  LIMITS  MAIN  BREAKUP  Apr-1  ICE  SEASON  OF  Ice Limits th  5  April  '5  Apnl  2 5 frt  fh  Opei  U  E  B  E  C  A R E A S 1951  May  1st  May  5 '" NO  A'a'er Apnl  SC»ll H I M A P  2 0l t t S M  DATA  5 !f  40  2 0  O  V  «•  =r  . ^>  T E M P E RAT O R E  •  •  •  >  *  •i  •-t  >  i -  >  4  c  %  N O V 4  1950  DEC  19 5 0  J A N  1951  F E B  1951  M A R  1951  A P R  1951 •  59  64  

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