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UBC Theses and Dissertations

Study of the density structure and water flow in the upper 10 m. of a selected region in Bute Inlet,… Johns, Robert Eric 1968

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A STUDY OF THE DENSITY STRUCTURE AND WATER FLOW IN THE UPPER 10 M. OF A SELECTED REGION IN BUTE INLET, BRITISH COLUMBIA by ROBERT ERIC JOHNS B . S c , U n i v e r s i t y of V i c t o r i a , 1966 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE i n t h e Department of P h y s i c s and t h e I n s t i t u t e of Oceanography We accept t h i s t h e s i s as c o n f o r m i n g t o t h e r e q u i r e d s t a n d a r d THE UNIVERSITY OF BRITISH COLUMBIA September, 1968 In p r e s e n t i n g t h i s t h e s i s in p a r t i a l f u l f i l m e n t o f the r e q u i r e m e n t s f o r an advanced d e g r e e a t the U n i v e r s i t y o f B r i t i s h C o l u m b i a , I a g r e e t h a t the L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e and S t u d y . I f u r t h e r a g r e e t h a t p e r m i s s i o n f o r e x t e n s i v e c o p y i n g o f t h i s t h e s i s f o r s c h o l a r l y p u r p o s e s may be g r a n t e d by the Head o f my Department or by h i s r e p r e s e n t a t i v e s . It i s u n d e r s t o o d t h a t c o p y i n g or p u b l i c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l not be a l l o w e d w i t h o u t my. w r i t t e n p e r m i s s i o n . Department o f P h y s i c s The U n i v e r s i t y o f B r i t i s h Co lumbia V a n c o u v e r 8, Canada Date 26 September 1968 ABSTRACT An i n t e n s e p y c n o c l i n e at about 4 m. depth e x i s t e d i n Bute I n l e t i n August, 1967. T h i s c o r r e s p o n d e d t o t h e l a r g e s t o b s e r v e d f r e s h water r u n o f f i n t o t h e head of t h e i n l e t . A major p y c n o c l i n e above 10 m. depth was not o b s e r v e d i n January, 1968, c o r r e s p o n d i n g t o s m a l l f r e s h water r u n o f f . C o r r e l a t i n g i n f o r m a t i o n d e r i v e d from n e a r - s u r f a c e t r a n s v e r s e and l o n g i t u d i n a l sigma-t s e c t i o n s and d r i f t p o l e p l o t s w i t h w ind and t i d e d a t a , t h e c u r v a t u r e of t h e i n l e t ' s l a t e r a l b o u n d a r i e s was found t o i n f l u e n c e t h e d i s p o s i t i o n of f r e s h water i n any g i v e n t r a n s v e r s e s e c t i o n . The d i r e c t i o n of t h e s u r f a c e l a y e r f l o w was bes t r e l a t e d t o t h e wind d i r e c t i o n except i n ca s e s of h i g h r u n o f f when the wind o n l y modulated t h e speed of o u t f l o w . The t i d e had r e m a r k a b l y l i t t l e e f f e c t . D i s t i n c t changes i n depth of t h e p y c n o c l i n e a l o n g i n l e t were ob-s e r v e d . S u g g e s t i o n s f o r f u t u r e e x p e r i m e n t s a re p r e s e n t e d . i i i TABLE OF CONTENTS Page I INTRODUCTION G e n e r a l d e s c r i p t i o n 1 Purpose of s t u d y 1 I I PROCEDURE C r u i s e s 3 T r a n s v e r s e s e c t i o n s 3 Radar and communications 3 Workboat o p e r a t i o n s 5 I I I INSTRUMENTS In s i t u s a l i n o m e t e r 6 V e r t i c a l s p a c i n g of measurements 6 C a l i b r a t i o n of s a l i n o m e t e r 6 Need f o r depth sensor and c o n t i n u o u s r e c o r d i n g c a p a b i l i t y 7 H y d r o g r a p h i c s t a t i o n s 7 D r i f t p o l e s 8 Wind o b s e r v a t i o n s 8 IV UNCERTAINTIES S u r f a c e d r i f t of workboat 1 0 Wire a n g l e s 1 0 A c c u r a c y of temp e r a t u r e and s a l i n i t y measurements 1 1 Sampling scheme 1 2 i v Page V ANALYSIS C a l c u l a t i o n of sigma-t v a l u e s 14 C a l c u l a t i o n of c u r r e n t speeds 14 Treatment of wind d a t a 21 VI RESULTS I n t e n s i t y of p y c n o c l i n e 22 F r e s h water r u n o f f 22 H y d r o g r a p h i c s t a t i o n d a t a 22 Summer regime . . . -. 27 Autumn regime 35 Winter regime 48 V I I DISCUSSION G e n e r a l f e a t u r e s of f l o w 53 I n f l u e n c e of l a t e r a l b o u n d a r i e s 53 D i r e c t i o n of f l o w of s u r f a c e l a y e r 55 L i m i t e d e v i d e n c e of m i x i n g 57 Marked changes i n depth of p y c n o c l i n e a l o n g - i n l e t 58 I n t e r n a l waves 58 V I I I SUMMARY 61 IX SUGGESTIONS FOR FUTURE EXPERIMENTATION Q u e s t i o n s r a i s e d by s t u d y 63 E x t e n s i o n s t o r e s e a r c h 64 Cho i c e of sensor 64 V Page BIBLIOGRAPHY 66 APPENDICES I T r a n s p o r t c a l c u l a t i o n s 68 I I R e l a t i o n between f r e s h water r u n o f f and s u r f a c e l a y e r s a l i n i t y 7 3 v i LIST OF TABLES T a b l e Page I C r u i s e i n f o r m a t i o n 4 I I D e n s i t y and c u r r e n t d a t a summary . . . . . . . . 15 I I I C e n t r i p e t a l and C o r i o l i s a c c e l e r a t i o n s f o r s e c t i o n B 56 Appendix: Observed and c a l c u l a t e d s u r f a c e l a y e r t r a n s p o r t s 72 v i i LIST OF FIGURES Figure Page 1 Bute I n l e t , showing s t a t i o n p o s i t i o n s 2 2 D r i f t pole c o n s t r u c t i o n 9 3 Winds, as measured from anchored ship . . . 16, 17 4 Tides at Waddington Harbour, head of Bute I n l e t 18, 19 5 Fresh water r u n o f f , Homathko River 20 6 Sigma-t p r o f i l e f o r s t a t i o n Bu 4, 15 August 1967, 1405 P.S.T 23 7 Temperature-salinity diagram corresponding to the 15 August 1967 p r o f i l e 24 8 Sigma-t p r o f i l e f o r s t a t i o n Bu 4, 3 January 1968, 0928 P.S.T 25 9 Tem p e r a t u r e - s a l i n i t y diagram corresponding to the 3 January 1968 p r o f i l e 26 10 Transverse sigma-t s e c t i o n A, 16 August 1967. . 28 11 Transverse sigma-t s e c t i o n B, 16 August 1967. . 29 12 D r i f t pole t r a c k s f o r 16 August 1967 30 13 Transverse sigma-t s e c t i o n A, 17 August 1967. . 31 14 Transverse sigma-t s e c t i o n B, 17 August 1967. . 32 15 D r i f t pole t r a c k s for 17 August 1967 33 16 D r i f t pole t r a c k s for 17 August 1967 36 17 L o n g i t u d i n a l sigma-t s e c t i o n , 18 August 1967. . 37 18 Transverse sigma-t s e c t i o n A, 14 September 1967 39 v i i i Figure Page 19 Transverse sigma-t section B, 14 September 1967 40 20 D r i f t pole tracks for 14 September 1967 . . . . 41 21 D r i f t pole tracks for 13 September 1967 . . . . 42 22 D e t a i l of flow near Alpha Bluff 44 23 Longitudinal sigma-t section, 15 September 1967 45 24 Transverse sigma-t section A, 30 November 1967. 46 25 Transverse sigma-t section B, 30 November 1967. 47 26 Longitudinal sigma-t section, 29 November 1967. 49 27 Longitudinal sigma-t section, 1 December 1967 . 50 28 D r i f t pole track for 4 January 1968 52 29 Si m p l i f i e d diagram for case of down-inlet surface flow 54 Appendix: Plot of average surface layer s a l i n i t y as a function of average fresh water runoff 74 ACKNOWLEDGMENTS I w i s h t o e x p r e s s my s i n c e r e t h a n k s t o my s u p e r v i s o r , Dr. G. L. P i c k a r d , f o r h i s guidance throughout t h e c o u r s e of t h i s i n v e s t i g a t i o n . I would a l s o l i k e t o thank Dr. R. W. Stewart f o r h i s h e l p f u l comments. The a s s i s t a n c e of the o f f i c e r s and crews of t h e C.S.S. E h k o l i , t h e C.N.A.V. Endeavour and the C.S.S. V e c t o r d u r i n g the f i e l d work i n Bute I n l e t was v e r y much a p p r e c i a t e d . I am v e r y g r a t e f u l t o Mr. M. P. Storm f o r h i s a d v i c e and a s s i s t a n c e both aboard s h i p and i n the l a b o r a t o r y . 1 INTRODUCTION The c o a s t of B r i t i s h Columbia i s i n d e n t e d w i t h many l o n g , narrow b o d i e s of water. T y p i c a l of t h e l a r g e r u n o f f i n l e t s i s Bute I n l e t ( f i g . 1 ) . I t i s about 75 km. i n l e n g t h from head t o mouth; i t averages 3^ km. i n w i d t h ; and i t rang e s from about 200 m. depth near the head, through 650 m. h a l f way down i n l e t , t o 350 m. near t h e mouth. D u r i n g t h e months of May th r o u g h August when the f r e s h water r u n o f f i s at i t s peak, an i n t e n s e h a l o c l i n e i s formed d i v i d i n g t h e r u n o f f - d e r i v e d s u r f a c e l a y e r from t h e s a l i n e w a t e r s below. The o c e a n o g r a p h i c s t r u c t u r e of the i n l e t has been d e s c r i b e d i n d e t a i l by Tabata and P i c k a r d (1957) and P i c k a r d (1961). The purpose of t h e p r e s e n t s t u d y has been t o o b t a i n a b e t t e r q u a l i t a t i v e u n d e r s t a n d i n g of t h e n a t u r e of t h e s u r f a c e f l o w i n r e l a t i o n t o the f r e s h / s a l t water i n t e r f a c e i n t h e neighborhood of a h o r i z o n t a l c o n s t r i c t i o n about h a l f way down i n l e t from the head. 3 PROCEDURE S i x c r u i s e s were completed d u r i n g t h e p e r i o d June 1967 t o January 1968; a summary of t h e s e i s p r e s e n t e d i n t a b l e I . The f i r s t t h r e e , i n June, August, and Septem-be r , were aboard the C.S.S. E h k o l i . The two c r u i s e s i n October and November were aboard the C.N.A.V. Endeavour. The l a s t c r u i s e i n January was aboard t h e C.S.S. V e c t o r . The s c i e n t i f i c p e r s o n n e l on a l l c r u i s e s were m y s e l f and one a s s i s t a n t . D u r i n g t h e e x p e r i m e n t a l program, t h e s h i p was anchored i n mi d - c h a n n e l a p p r o x i m a t e l y h a l f way between s e c t i o n s A and B ( d e s c r i b e d below) i n a p o s i t i o n e n a b l i n g a d i r e c t l i n e - o f - s i g h t , t o a l l s t a t i o n s . Measurements were c a r r i e d out away from t h e s h i p d u r i n g d a y l i g h t hours by workboat. I n i t i a l l y , f o u r shore markers c o n s i s t i n g of a r o c k f a c e p a i n t e d w i t h whitewash were e s t a b l i s h e d t o i d e n t i f y two s e c t i o n s a c r o s s i n l e t ( f i g . 1 ) , t h e c e n t e r s t a t i o n s , A3 and B3, b e i n g 2.3 km. a p a r t . Whitewash shore markers were used m a i n l y t o ensure r e p e a t a b i l i t y of s t a t i o n p o s i t i o n s from c r u i s e t o c r u i s e . The s h i p ' s r a d a r was used t o p o s i t i o n t h e workboat on s t a t i o n by d i r e c t i n g t h e boat i n such a manner t h a t i t s r a d a r echo became a l i g n e d w i t h a dot r e p r e s e n t i n g the s t a t i o n marked on a p l a s t i c sheet p l a c e d over the r a d a r s c r e e n . Commu-TABLE I : CRUISE INFORMATION Cr. No. Dates V e s s e l P e r s o n n e l Remarks 67/17 26-30 June 1967 C.S.S. E h k o l i R .E. Johns, M.P. Storm Survey c r u i s e o n l y 67/22 14-20 Aug. 1967 C.S.S. E h k o l i R .E. Johns, M.P. Storm 67/25 10-18 Sept. 1967 C.S.S. E h k o l i R . E. Johns, M. S l a t e r 67/27 16-21 Oct. 1967 C.N.A.V. Endeavour R .E. Johns, A.S. B a i n Equipment f a i l u r e ; d a t a o m i t t e d from a n a l y s i s . 67/30 27 Nov.-2 Dec. 1967 C.N.A.V. Endeavour R .E. Johns, M.P. Storm 68/1 2-8 Jan. 1968 C.S.S. V e c t o r R .E. Johns, M.P. Storm 5 n i c a t i o n s w i t h the workboat were by r a d i o i n t h e 27 mHz. band. D i f f i c u l t i e s were e x p e r i e n c e d w i t h commu-n i c a t i o n s , e s p e c i a l l y d u r i n g the f i r s t f o u r c r u i s e s . Not o n l y was the equipment inadequate (100 m i l l i w a t t h a n d s e t s ) , but s k i p c o n d i t i o n s e n a b l i n g s i g n a l s from C a l i f o r n i a t o be he a r d , a h i g h l e v e l of e l e c t r i c a l n o i s e aboard t h e workboat, and the i n a b i l i t y t o p l a c e the s h i p -based handset near t h e r a d a r c o n s o l e a l l c o n t r i b u t e d t o many f r u s t r a t i n g d e l a y s . For the l a s t two c r u i s e s , new, 2 w a t t , 2 c h a n n e l h a n d s e t s w i t h remote antennas were used. These overcame almost a l l d i f f i c u l t i e s , except t h a t as b e f o r e the workboat's engine had t o be slowed down t o e n a b l e t h e s i g n a l t o be h e a r d above t h e background a c o u s t i c n o i s e . Workboat o p e r a t i o n s c o n s i s t e d of t a k i n g t e m p e r a t u r e and s a l i n i t y p r o f i l e s , and t h e deployment and r e c o v e r y of s u r f a c e d r i f t p o l e s . Wind and s e l e c t e d o t h e r m e t e o r o l o g i c a l v a r i a b l e s were o b s e r v e d from the s h i p . 6 INSTRUMENTS The t e m p e r a t u r e and s a l i n i t y p r o f i l e s were t a k e n w i t h an _in s i t u , i n d u c t i v e s a l i n o m e t e r ( I n d u s -t r i a l I n s t r u m e n t s Corp., Cedar Grove, N.J., model RS5-2). In view of the r e l a t i v e l y l a r g e v e r t i c a l g r a d i e n t s en-c o u n t e r e d , t h e temperature was r e c o r d e d t o t h e n e a r e s t 0.1 C°., and t h e s a l i n i t y t o the n e a r e s t 0.1 o/oo. Some measurements f l u c t u a t e d r a p i d l y i n t i m e ; t h e extremes f o r t h e s e c a s e s were r e c o r d e d and t h e mean of t h e extremes t a k e n as the r e p r e s e n t a t i v e v a l u e . Depth was measured from metre markings on t h e c a b l e w i t h c o r r e c t i o n s f o r n o n - v e r t i c a l c a b l e from e s t i m a t e s of t h e angl e at t h e s u r f a c e , t h e measurements b e i n g t a k e n i n 1 or 2 m. i n -t e r v a l s down t o 10 or 15 m., depending on t h e p r e v a i l i n g c o n d i t i o n s . Measurements t a k e n subsequent t o t h o s e i n August i n c l u d e d r e a d i n g s at \ m. i n t e r v a l s w i t h i n the p y c n o c l i n e . E s s e n t i a l l y no more u s e f u l i n f o r m a t i o n c o u l d be g a i n e d by an even c l o s e r s p a c i n g because of t h e f i n i t e volume of water t h a t i s sensed by t h e i n s t r u m e n t , as d e s c r i b e d l a t e r . C a l i b r a t i o n of t h e s a l i n i t y sensor was a c h i e v e d by d i l u t i o n of a sea water sample i n s t e p s w i t h d i s t i l l e d w a t e r , t h e i n s i t u sensor r e a d i n g at each d i -l u t i o n b e i n g compared t o a d e t e r m i n a t i o n w i t h a l a b o r a t o r y 7 i n d u c t i v e saline-meter (Auto-Lab I n d u s t r i e s , Sydney, model 601, mk. I I I ) . Temperatures were compared a g a i n s t t h e r e a d i n g s of a mercury thermometer. F i n a l l y , a l e a s t s q u a r e s s t r a i g h t l i n e was f i t t e d t o a s i n g l e s e t of c a l i -b r a t i o n v a l u e s . T h i s was j u s t i f i e d on the b a s i s t h a t t h e range of s a l i n i t i e s at any g i v e n s t a t i o n was l a r g e compared t o t h e t y p i c a l c a l i b r a t i o n c o r r e c t i o n (~ 0.1 o/oo). F u r t h e r , t h e d e n s i t y f u n c t i o n was i n s e n s i t i v e t o tempera-t u r e changes of t h e o r d e r of t h e c a l i b r a t i o n c o r r e c t i o n (~ 1 C°.). To a v o i d t h e depth u n c e r t a i n t i e s t h a t a r i s e at l a r g e c a b l e a n g l e s , i t would be a d v i s a b l e t o i n c l u d e a depth sensor i n t h e i n s t r u m e n t package f o r any f u t u r e measurements. An output i n a format s u i t a b l e f o r c o n t i n u o u s r e c o r d i n g of s a l i n i t y v s . depth and tem-p e r a t u r e v s . depth would a l s o be p r e f e r a b l e . I t i s un-l i k e l y t o be p r a c t i c a l t o m o d i f y th e p r e s e n t i n s t r u m e n t t o e n a b l e th e o f f - b a l a n c e s i g n a l t o be r e c o r d e d because of t h e l a r g e t e m p e r a t u r e and s a l i n i t y g r a d i e n t s one en-c o u n t e r s i n t h e i n l e t . At t h e b e g i n n i n g and end of each c r u i s e s e r i a l o b s e r v a t i o n s of t e m p e r a t u r e and s a l i n i t y were made t o 600 m. depth near t o t h e anchor s t a t i o n u s i n g A t l a s s a m p l i n g b o t t l e s . These d a t a are a v a i l a b l e i n Data R e p o r t s 8 of t h e I n s t i t u t e of Oceanography ( U n i v e r s i t y of B r i t i s h Columbia. I n s t i t u t e of Oceanography. 1968a, 1968b). A s t u d y of t h e s u r f a c e c u r r e n t s was c a r -r i e d out w i t h d r i f t p o l e s , c o n s t r u c t e d as shown i n f i g . 2. The deployment pro c e d u r e c o n s i s t e d of o c c u p y i n g a s t a t i o n f o r p r o f i l e measurements, l e t t i n g out one p o l e , t h e n p r o c e e d i n g t o t h e next s t a t i o n . The d r i f t i n t ime of each p o l e was p l o t t e d from th e r a d a r s c r e e n on a p l a s -t i c o v e r l a y . The e f f e c t i v e s i g n a l - t o - n o i s e r a t i o by t h i s method was f a r s u p e r i o r t o a p h o t o g r a p h i c t e c h n i q u e because of t h e eye's a b i l i t y t o c o r r e l a t e s u c c e s s i v e sweeps of the r a d a r t r a c e . As f o r t h e m e t e o r o l o g i c a l o b s e r v a t i o n s , i t became o b v i o u s t h a t the one p e r s o n aboard c o u l d not both monitor t h e r a d a r and t a k e h o u r l y weather o b s e r v a t i o n s . For t h i s r e a s o n , some of the d a t a were o b s e r v e d by the s c i e n t i f i c p e r s o n n e l , w h i l e the b u l k of the d a t a was e x t r a c t e d from th e s h i p ' s l o g . The anemometer mounted at the mast head p r o v i d e d t h e wind i n f o r m a t i o n . ALUMINUM RADAR R E F L E C T O R 8 I 5 SO. ^ 1 P L A S T I C F L O T A T I O N M A T E R I A L A L L MATERIALS WOOD E X C E P T AS SPECIFIED « 0 " 4 ' 8 f ' r 6 -j " PLYWOOD VANES (PLAN VIEW) WIRE I 5 L B . L E A D BALLAST F i g . 2. D r i f t p o l e c o n s t r u c t i o n . 10 UNCERTAINTIES S p a t i a l u n c e r t a i n t i e s i n s u r f a c e p o s i t i o n and depth and u n c e r t a i n t i e s a s s o c i a t e d w i t h p r o c e s s e s whose t i m e s c a l e s are unknown r e p r e s e n t t h e p r i n c i p a l s o u r c e s of p o s s i b l e e r r o r . These and o t h e r u n c e r t a i n t i e s w i l l be d i s c u s s e d i n t h e f o l l o w i n g p a r a g r a p h s . Because of the depth of the i n l e t ( i n e x c e s s of 600 m.), a n c h o r i n g t h e workboat w h i l e on s t a t i o n was i m p r a c t i c a l . The i n e v i t a b l e e f f e c t was t h a t the boat d r i f t e d as much as 1 km. w h i l e measurements were t a k e n . The d i r e c t i o n of t h i s d r i f t was g e n e r a l l y t h e same as t h a t of t h e water f l o w ( m o d i f i e d at t i m e s by a d i f f e r e n t wind d i r e c t i o n ) ; one can o n l y hope t h a t t h i s c o r r e s p o n d e d t o t h e d i r e c t i o n of t h e minimum h o r i z o n t a l d e n s i t y g r a d i e n t s . The l i m i t e d i n f o r m a t i o n a v a i l a b l e seems t o i n d i c a t e t h a t i t d i d . In any c a s e , t h e deeper measurements are more u n c e r t a i n t h a n the s h a l l o w ones because t h e boat was s t o p p e d on s t a t i o n and the n e a r -s u r f a c e measurements t a k e n f i r s t . As t h i s does not a l t e r the g e n e r a l c h a r a c t e r of t h e d e n s i t y s e c t i o n s , t h e un-c e r t a i n t y a s s o c i a t e d w i t h d r i f t i s not i n c l u d e d i n the f o l l o w i n g assessment. A s t r o n g c u r r e n t shear was e v i d e n t l y a s -s o c i a t e d w i t h t h e p y c n o c l i n e r e s u l t i n g i n l a r g e r w i r e 11 a n g l e s when the i n s t r u m e n t head was below about 4 m. depth. In f a c t , w i r e a n g l e s i n e x c e s s of 2 0 ° were common below about 6 m.; w i r e a n g l e s as l a r g e as 4 5 ° o c c u r r e d w i t h 10 m. of c a b l e o u t . T h i s , t o g e t h e r w i t h t h e r e s p o n s e of t h e boat (and hence th e i n s t r u m e n t ) t o s u r f a c e waves, g e n e r a t e d u n c e r t a i n t i e s i n depth at 4 m. of about \ m., i n c r e a s i n g t o 3/4 m. at 6 m. and 2 m. at 10 m. Temperature and s a l i n i t y measurements are c o n s i d e r e d a c c u r a t e t o ± 0 . 1 C ° . and ± 0 . 1 o/oo r e s p e c t i v e l y , except i n c a s e s when t h e s e v a r i a b l e s f l u c -t u a t e d r a p i d l y . R e p r e s e n t i n g the e r r o r i n t h e s e c a s e s as t h e sum of t h e a m p l i t u d e of t h e f l u c t u a t i n g s i g n a l and t h e s t a n d a r d d e v i a t i o n from t h e l e a s t s quares c a l i -b r a t i o n , t h e maximum r e s u l t i n g u n c e r t a i n t y i n sigma-t was 6 u n i t s . However, u n c e r t a i n t i e s of t h i s magnitude were not common, the u s u a l b e i n g l e s s t h a n 1 sigma-t u n i t . The p r e c e d i n g assessments of u n c e r t a i n t y do not t a k e i n t o c o n s i d e r a t i o n the f a c t t h a t t h e i n s t r u -ment sensor measures th e c o n d u c t i v i t y and hence s a l i n i t y of a volume of water s u r r o u n d i n g i t whose l e n g t h s c a l e i s about 1/3 m. T h i s s e t s a l i m i t t o the depth r e s o l u t i o n p o s s i b l e and adds an undetermined u n c e r t a i n t y t o t h e s a l i n i t y . The t e m p e r a t u r e r e s o l u t i o n i s s i g n i f i c a n t l y 12 b e t t e r ; t h e volume of water sensed has a l e n g t h s c a l e of about 1/10 m. E r r o r s i n the d r i f t p o l e p l o t s a r i s e c h i e f l y f rom t h e p a r a l l a x a s s o c i a t e d w i t h v i e w i n g t h e r a d a r s c r e e n . T h i s e f f e c t has been r e d u c e d by smoothing the d a t a , as d e s c r i b e d l a t e r . The o b s e r v a t i o n a l program c o n s i s t e d of c o m p l e t i n g t h e two s e c t i o n s , A and B, t w i c e d a i l y d u r i n g t h e 4 t o 5 w o r k i n g days a v a i l a b l e on each c r u i s e . C r u i s e s were r e p e a t e d e v e r y 4 t o 5 weeks from August 1967 t o January 1968. From a q u a n t i t a t i v e p o i n t of view, t h e n a t u r e of t h i s s a m p l i n g scheme i s such t h a t s h o r t time s c a l e phenomena such as t u r b u l e n c e and i n t e r n a l waves are m i s s e d e n t i r e l y and l o n g e r s c a l e p r o c e s s e s a s s o c i a t e d w i t h t i d a l and s e a s o n a l p e r i o d s are p o o r l y d e f i n e d . With t h e l i m i t e d t i m e and p e r s o n n e l a v a i l a b l e , even a crude t i m e s e r i e s of one or two days d u r a t i o n at one s t a t i o n was not p o s s i b l e w i t h o u t s a c r i f i c i n g the time n e c e s s a r y t o o b t a i n a minimum number of t r a n s v e r s e den-s i t y s e c t i o n s . A r e l a t e d problem i s t h e i n t e r p r e t a t i o n of t h e two s e c t i o n s as b e i n g s i m u l t a n e o u s . I n a c t u a l f a c t , 2 hours were r e q u i r e d t o complete both s e c t i o n s . One may not be j u s t i f i e d i n comparing d e t a i l s o b s e r v e d 13 at t h e f i r s t s t a t i o n w i t h t h o s e o b s e r v e d at the l a s t . However, th e importance of t h i s i s unknown, and the s e c -t i o n s have been r e g a r d e d as though t a k e n s i m u l t a n e o u s l y (at l e a s t i n t h e i r major c h a r a c t e r i s t i c s ) . 14 ANALYSIS Knudsen sigma-t v a l u e s were computed on the U n i v e r s i t y ' s I.B.M. 7044 from t h e measured tempera-t u r e and s a l i n i t y d a t a . The change i n sigma-t f o r a change i n tem p e r a t u r e was v e r y much s m a l l e r t h a n t h e change i n sigma-t f o r a change i n s a l i n i t y w i t h i n the range of tem p e r a t u r e and s a l i n i t y e n c o u n t e r e d ( s e e , f o r example, f i g . 7 and 9 ) . P r o f i l e s of t h e computed sigma-t v s . depth were p l o t t e d by a Calcomp p l o t t e r . A best f i t l i n e was drawn by hand t o f i t t h e p o i n t s ; t r a n s v e r s e and l o n g i t u d i n a l s e c t i o n s were p l o t t e d u s i n g i n t e r p o l a t e d v a l u e s from t h e s e p r o f i l e s . To o b t a i n c u r r e n t i n f o r m a t i o n , the d r i f t p o l e d i s p l a c e m e n t s were p l o t t e d a g a i n s t t h e c o r r e s p o n d i n g e l a p s e d t i m e s and a smooth c u r v e drawn through the p o i n t s . The d i s p l a c e m e n t s i n u n i f o r m time i n t e r v a l s were r e a d from t h e s e graphs and marked on t h e d r i f t p o l e t r a c k s . The speeds were de t e r m i n e d from t h e s l o p e s of t h e graphs. A summary of t h e d e n s i t y and c u r r e n t d a t a i s p r e s e n t e d i n t a b l e I I , t h e wind and t i d e d a t a are shown i n f i g . 3 and 4, and t h e f r e s h water r u n o f f i s p l o t t e d i n f i g . 5. The t i d e p r e d i c t i o n s were o b t a i n e d from t h e Canadian T i d e and C u r r e n t T a b l e s , 1967 and 1968, n e g l e c t i n g t h e a p p r o x i m a t e l y 9 min. d i f f e r e n c e i n t i m e s TABLE I I : DENSITY AND CURRENT DATA SUMMARY Cr. No. 67/17 67/22 67/25 67/30 68/1 T r a n s v e r s e A Sect i o n s 0 4 3 4 5 Number of T r a n s v e r s e B L o n g i t u d i n a l Sect i o n s 3 4 2 3 5 Sect i o n s 0 1 2 2 1 C u r r e n t P l o t s 0 4 5 0 3 i o r a. 3 H - 2 _Jo Zo f , 0 O Oo. cr o 0 o j=IO o UJ — 3 . Q Q 0 2 z <5 o *-~.Q LJIO CO \ 5 = a U 0 o Q ? I 0 a. z o o 12 28 J U N E '67 18 A U G . ' 67 1 T I M E (P.S.T.) 0Q_ 2 9 J U N E ' 6 7 12 S E P T . ' 67 16 10 13 S E P T . '6 7 15 S E P T . '67 14 S E P T . '67 F i g . 3. Winds, as measured from anchored s h i p . 0 0 12 0 0 12 0 0 10 a. po l LU I 2 2 5 ~7 O .00 12 T I M E (RS.T.) 0 0 12 17 0 0 \ / \ 2 8 NOV. '67 10 2 9 N O V . '67 — I o o a. CC =3 O oL 01 o 10 o LU CC 3 0 NOV. '67 I DEC. '67 — h o 0 1 2 2 «§ Euioi CO 25 So* a 3 J A N . 6 8 4 J A N . 6 8 5 J A N . '68 :I0 6 J A N . 68 + F i g . 3 ( c o n t i n u e d ) . Winds," as measured from anchored s h i p . a. => 2 O a 7 J A N . '68 I0 L 0 0 12 0 0 12 0 0 .00 12 T I M E (P.S.T.) 00 12 18 00 28 JUNE "67 _ _4_ 29 JUNE '67 I-<2 Q < b X o 4 UJ > o < 2 x 4 18 AUG. '67 12 SEPT. '67 0 6 13 SEPT. '67 14 SEPT. '67 4 k 00 F i g . 4. T i d e s at Waddington Harbour, head of Bute I n l e t . 15 SEPT. '67 12 00 12 00 00 61 12 T I M E (RS.T.) 0 0 1 12 19 0 0 2 Q| 28 NOV. 29 NOV. '67 3 4 < o 2 h-a: £> 5e UJ . > 4 o CD < 2 o UJ 1 4 2 0 5 JAN. '68 6 JAN. '68 01 00 7 JAN. '68 i 12 00 F i g . 4 ( c o n t i n u e d ) . T i d e s at Waddington Harbour, head of Bute I n l e t . 12 00 1200 1000 o UJ CO 8 0 0 UJ o or < 6 0 0 x o CO 4 0 0 2 0 0 F i g . 5. F r e s h water r u n o f f , Homathko R i v e r (Canada. Dept. of Energy, Mines, & Re s o u r c e s . I n l a n d Waters Branch.) x •o 1967-8 -x LONG TERM MEAN (TRITES, 1955) • x ^ UPPER LIMIT ONLY; GAUGE NOT FUNCTIONING PROPERLY. J_ J_ JUNE J U L Y AUGUST SEPTEMBER OCTOBER NOVEMBER DECEMBER JANUARY of h i g h water between Waddington Harbour at t h e head of Bute I n l e t and t h e anchor s t a t i o n , as p r e d i c t e d by s h a l -low water wave t h e o r y ; t h e r u n o f f d a t a were computed by the I n l a n d Waters Branch of the Department of Energy, Mines, and R e s o u r c e s . A l t h o u g h the exact v a r i a t i o n s i n p o s i t i o n of t h e s h i p w h i l e at anchor were not r e c o r d e d , q u a l i t a -t i v e l y , t h e s h i p not o n l y swung i n an a r c about i t s anchor but at t i m e s d u r i n g s t r o n g winds d o w n - i n l e t a c t u a l l y dragged i t s anchor some d i s t a n c e . I n view of t h i s un-c e r t a i n t y i n t h e s h i p ' s p o s i t i o n , no attempt has been made t o c a l c u l a t e t h e a l o n g - i n l e t component of t h e wind from the wind d a t a . I n s t e a d , wind v e l o c i t i e s have been r e p o r t e d as u p - i n l e t i f t h e i r d i r e c t i o n s were from between 160° and 240° t r u e and d o w n - i n l e t i f t h e i r d i r e c t i o n s were from between 060° and 290° t r u e . Any wind whose d i r e c t i o n was o u t s i d e t h e s e l i m i t s has been i n t e r p r e t e d as up- or d o w n - i n l e t depending on t h e wind d i r e c t i o n s i m m e d i a t e l y p r e c e d i n g and f o l l o w i n g the p a r t i c u l a r ob-s e r v a t i o n . 22 RESULTS A l t h o u g h s e v e r a l s e t s of d a t a were t a k e n under s i m i l a r c o n d i t i o n s , o n l y t y p i c a l examples w i l l be r e f e r r e d t o i n t h e f o l l o w i n g p a r a g r a p h s . As the most s i g n i f i c a n t d i r e c t i o n s are a l o n g the a x i s of t h e i n l e t , th e terms " d o w n - i n l e t " and " u p - i n l e t " w i l l be used t o d e s c r i b e movements seaward from t h e head t o t h e mouth and i n l a n d from t h e mouth t o t h e head r e s p e c t i v e l y . The most o b v i o u s f e a t u r e t o be o b s e r v e d i n t h e d e n s i t y d a t a i s the i n t e n s i t y of t h e p y c n o c l i n e i n summer and e a r l y autumn. D u r i n g t h i s p e r i o d , t y p i -c a l l y t h e sigma-t v a l u e s r a n g e d from about 3 near the s u r f a c e , t h r o u g h about 6 at 4 m. t o about 18 at 5 m. and about 20 at 7 m. D u r i n g w i n t e r , t h e s u r f a c e l a y e r was e s s e n t i a l l y homogeneous, h a v i n g a sigma-t of about 22 down t o at l e a s t 10 m. i n January. F r e s h water r u n -o f f , as computed by t h e I n l a n d Waters Branch and shown i n f i g . 5, was g r e a t e s t i n June and d e c r e a s e d t o about a t e n t h of t h e June v a l u e i n November and e a r l y January. I t i s , i n f a c t , t h i s s e a s o n a l v a r i a t i o n i n r u n o f f which i s r e s p o n s i b l e f o r t h e l a r g e s e a s o n a l change i n the n e a r -s u r f a c e d e n s i t y s t r u c t u r e . P r o f i l e s of sigma-t and the c o r r e s p o n d i n g t e m p e r a t u r e - s a l i n i t y diagrams are shown i n f i g s . 6, 7, 8, and 9 f o r August and January as r e p r e s e n t a t i v e of summer 10 SIGMA-T 15 20 25 30 T r \ \ \ HI00 F i g . 6. Sigma-t p r o f i l e f o r s t a t i o n Bu 4, 15 August 1967, 1405 P.S.T. H 4 0 0 JLJL F i g . 7. T e m p e r a t u r e - s a l i n i t y diagram c o r r e s p o n d i n g t o t h e 15 August 1967 p r o f i l e . 10 SIGMA-T 15 20 25 30 T Fig. 8. Sigma-t p r o f i l e for sta t i o n Bu 4, 3 January 1968, 0928 P.S.T. 2 5 2 6 i r 2 7 S A L I N I T Y (%o) 2 8 2 9 26 30 31 T T 10 o o . UJ or f— UJ Q. UJ 8 q = 2 0 0"f » 2 2 •oo. ,oojg 0 °« 5 0 0 , 1 1 5 0 6 0 0 F i g . 9. T e m p e r a t u r e - s a l i n i t y diagram c o r r e s p o n d i n g t o t h e 3 January 1968 p r o f i l e . and w i n t e r p e r i o d s . The c o n d i t i o n s d e p i c t e d are of t h e same c h a r a c t e r as t h o s e o b s e r v e d by T abata and P i c k a r d (1957) and P i c k a r d (1961). D i f f e r e n c e s i n water p r o p e r -t i e s between the summer and w i n t e r p e r i o d s o c c u r r e d p r i -m a r i l y i n t h e upper 75 m. The d e t a i l e d d e n s i t y and c u r r e n t d a t a are best grouped a c c o r d i n g t o season, which i s the same as a c c o r d i n g t o t h e average amount of f r e s h water r u n o f f f l o w i n g seaward. The wind and t h e s t a t e of t h e t i d e a re t h e o t h e r s i g n i f i c a n t v a r i a b l e s . SUMMER August f a l l s i n t h e l a t t e r p a r t of t h e summer season i n Bute. The s u r f a c e l a y e r f l o w e d down-i n l e t t hroughout th e t i d a l c y c l e , w i t h a f r e s h water t r a n s p o r t at t h e head of 840 m. 3/sec. The d e n s i t y s t r u c -t u r e was c h a r a c t e r i z e d by an i n t e n s e p y c n o c l i n e c e n t e r e d around 3 t o 4 m., w i t h sigma-t v a l u e s above i t of 2 t o 4. T y p i c a l g r a d i e n t s w i t h i n t h e p y c n o c l i n e were 8 sigma-t u n i t s per metre. In the t r a n s v e r s e s e c t i o n s the low s i g m a - t , i . e . , f r e s h w a t e r , was c o n c e n t r a t e d t o t h e r i g h t of t h e f l o w d i r e c t i o n at s e c t i o n A and g e n e r a l l y t o t h e l e f t of t h e f l o w d i r e c t i o n at s e c t i o n B. T y p i c a l examples are shown i n f i g s . 10 t h r o u g h 15. I t s h o u l d be mentioned F i g . 10. T r a n s v e r s e sigma-t s e c t i o n A, 16 August 1967. S t a t i o n numbers g i v e n a l o n g t o p w i t h c o r r e s p o n d i n g t i m e s ( P . S . T . ) . to o o BKI355 ) B2 0345) B3(I335) B40325) B503I5) Oi 1 1 • 1 1 ' to CD 30 1 • • • • i • i | 0 500 1000 2000 _ S C A L E (M.) F i g . 12. D r i f t p o l e t r a c k s f o r 16 August 1967, showing s t a r t i n g t i m e s (P.S.T.) and average speeds (cm./sec.) f o r each 20 min. i n t e r v a l . Al (1145) A202OO) A3 (1215) A40226) A5(I240) F i g . 13. T r a n s v e r s e sigma-t s e c t i o n A, 17 August 1967. S t a t i o n numbers g i v e n a l o n g t o p w i t h c o r r e s p o n d i n g t i m e s ( P . S . T . ) . 0 B I 0 3 3 5 ) B2 0326) B3(I345) .84(1315) B503O3) i i I I i ~ 4 I Q. LU Q 6 8 F i g . 14. T r a n s v e r s e sigma-t s e c t i o n B, 17 August 1967. S t a t i o n numbers g i v e n a l o n g t o p w i t h c o r r e s p o n d i n g t i m e s (P.S.T.). w to 33 I • • • • I I I O 500 1000 2000 S C A L E (M. ) ; F i g . 15. D r i f t p o l e t r a c k s f o r 17 August 1967, showing s t a r t i n g t i m e s (P.S.T.) and average speeds (cm./sec.) f o r each 20 min. i n t e r v a l . 34 t h a t s e c t i o n B i s somewhat upstream of t h e O r f o r d R i v e r . I t i s u n l i k e l y t h a t t h e water from t h i s r i v e r would p r o -g r e s s upstream a g a i n s t t h e g e n e r a l s u r f a c e o u t f l o w , and t h e r e f o r e i t i s c o n s i d e r e d t o be not r e s p o n s i b l e f o r t h e d i s p o s i t i o n of f r e s h water i n s e c t i o n B. A s i g n i f i c a n t d i f f e r e n c e e x i s t s i n t h e c h a r a c t e r of t h e p y c n o c l i n e between t h e 16 August ( f i g . 10 and 11) and 17 August ( f i g . 13 and 14) c a s e s . D u r i n g the a p p r o x i m a t e l y 24 hours which s e p a r a t e t h e s e s e c t i o n s , t h e p y c n o c l i n e i n -t e n s i f i e d at A and weakened at B by a l t e r i n g the r e l a -t i v e s p a c i n g of t h e i s o p y c n a l s w i t h i n t h e p y c n o c l i n e w i t h -out s i g n i f i c a n t l y c h a n g i n g t h e depth of t h e p y c n o c l i n e ' s upper boundary. Indeed, t h e change at A o c c u r r e d over a p e r i o d of o n l y about 4 hours subsequent t o 0800 on the 1 7 t h , and p e r s i s t e d f o r at l e a s t 5 hours a f t e r t h e d a t a f o r t h e s e c t i o n s shown i n f i g . 13 and 14 were t a k e n . In c o n t r a s t t o t h e changes which o c c u r r e d below about 3 m., o n l y minor d i f f e r e n c e s were o b s e r v e d i n t h e d e n s i t y s t r u c t u r e of t h e s u r f a c e l a y e r i n t h e same 24 hour p e r i o d d u r i n g c a s e s of a d o w n - i n l e t wind of 4 m./sec. w i t h a d o w n - i n l e t f l o w i n g t i d e , a v a r i a b l e up-i n l e t w i nd of 1 t o 5 m./sec. w i t h an u p - i n l e t t i d e , and an u p - i n l e t wind of 7 m./sec. w i t h a d o w n - i n l e t t i d e . D r i f t p o l e s s t a r t i n g from s t a t i o n s A l 35 and A5 were always d i s p l a c e d l e s s t h a n t h o s e s t a r t i n g from s t a t i o n s A2, A3, and A4 d u r i n g the same i n t e r v a l of t i m e , i n d i c a t i n g t h a t t h e f l o w does not occupy t h e complete w i d t h of t h e i n l e t at s e c t i o n A. F i g . 16, c o r -r e s p o n d i n g t o 5 t o 8 m./sec. u p - i n l e t winds and a t i d e f l o w i n g d o w n - i n l e t , i s an example of t h i s . F u r t h e r m o r e , i t demonstrates t h a t t h e d r i f t p o l e s do i n d e e d r e s p o n d p r i n c i p a l l y t o t h e water movement r a t h e r t h a n t o t h e wind. F i g . 17 i s a l o n g i t u d i n a l s e c t i o n t a k e n down t h e m i d d l e of the i n l e t . A v e r t i c a l p r o f i l e at any p o i n t i s s i m i l a r t o p r o f i l e s from t h e August A and B t r a n s v e r s e s e c t i o n s . The depth of t h e p y c n o c l i n e r e -mained r e l a t i v e l y c o n s t a n t a l o n g t h e s e c t i o n ; t h i s i s t o be compared l a t e r w i t h l o n g i t u d i n a l s e c t i o n s t a k e n i n September, November, and December. AUTUMN September r e p r e s e n t s a t r a n s i t i o n a l month. A p y c n o c l i n e of r e d u c e d i n t e n s i t y p e r s i s t e d around 3 t o 4m., w i t h sigma-t v a l u e s above i t r a n g i n g from 4 t o 8. T y p i c a l g r a d i e n t s w i t h i n t h e p y c n o c l i n e i n Sep-tember were 4 sigma-t u n i t s per metre. F r e s h water en-'s t e r e d t h e head of t h e i n l e t at about 440 m. / s e c . D u r i n g t h e absence of wind, t h e s u r f a c e l a y e r f l o w e d u p - i n l e t 36 I i i i i I I I 0 500 1000 2000 S C A L E (M.) _ . • F i g . 16. D r i f t p o l e t r a c k s f o r 17 August 1967, showing s t a r t i n g t i m e s (P.S.T.) and average speeds (cm./sec.) f o r each 20 min. i n t e r v a l . F i g . 17. L o n g i t u d i n a l sigma-t s e c t i o n , 18 August 1967. S t a t i o n p o s i t i o n s i n d i c a t e d a l o n g t o p w i t h c o r r e s p o n d i n g t i m e s ( P . S . T . ) ; d i s t a n c e (km.) d o w n - i n l e t of s t a t i o n B3 g i v e n a l o n g bottom. CO 38 w i t h an u p - i n l e t t i d e . F i g s . 18, 19, and 20 demonstrate t h e im-p o r t a n c e of t h e wind i n d e t e r m i n i n g t h e d i r e c t i o n of water movement d u r i n g t h i s p e r i o d of r e d u c e d r u n o f f . Here t h e t i d e was i n t h e m i d d l e and f i n a l s t a g e s of i t s u p - i n l e t f l o w d u r i n g t h e o b s e r v a t i o n s , whereas t h e wind had been b l o w i n g d o w n - i n l e t at 9 m./sec. f o r s e v e r a l hours p r e v i o u s l y , d e c r e a s i n g t o about 3 m./sec. near the end of t h e r u n . As i s shown i n t h e f i g u r e s , t h i s r e s u l t e d i n a l a r g e d o w n - i n l e t water v e l o c i t y and pronounced s l o p e s of t h e i s o p y c n a l s . The f l o w was a p p a r e n t l y a c c e l e r a t e d as i t p a s s e d through t h e narrow p o r t i o n of the i n l e t by A l p h a B l u f f . The s i t u a t i o n i l l u s t r a t e d i n f i g . 21 can be d i r e c t l y c o n t r a s t e d w i t h t h e p r e v i o u s example. The t i d e was f l o w i n g u p - i n l e t w i t h t h e wind b l o w i n g at t h e s m a l l e r v e l o c i t y of 5 m./sec. d o w n - i n l e t f o r s e v e r a l hours p r e c e d i n g t h e r u n , d e c r e a s i n g t o near z e r o at the end of t h e r u n . The most o b v i o u s d i f f e r e n c e i n t h e two c u r -r e n t p l o t s i s t h a t i n f i g . 21 ( r e p r e s e n t i n g lower wind v e l o c i t y ) t h e water v e l o c i t i e s d i r e c t e d d o w n - i n l e t are g e n e r a l l y l e s s than t h o s e shown i n f i g . 20 ( r e p r e s e n t i n g h i g h e r w i n d s ) . Here, t o o , d r i f t p o l e s s t a r t i n g from s t a t i o n s A l , A4, and A5 were caught i n back e d d i e s and Al (1215) 42 BI (1455) B2 0 4 4 5 ) B3 (1435) B404 I5 ) B5 (1400) J J L F i g . 19. T r a n s v e r s e sigma-t s e c t i o n B, 14 September 1967. S t a t i o n numbers g i v e n a l o n g t o p w i t h c o r r e s p o n d i n g t i m e s ( P . S . T . ) . o 41 500 1000 S C A L E (M.) 2000 F i g . 20. D r i f t p o l e t r a c k s f o r 14 September 1967, showing s t a r t i n g t i m e s (P.S.T.) and average speeds (cm./sec.) f o r each 20 min. i n t e r v a l . 42 0 500 1000 2000 S C A L E (M.) F i g . 21. D r i f t pole tracks for 13 September 1967, showing s t a r t i n g times (P.S.T.) and average speeds (cm./sec.) for each 20 min. i n t e r v a l . 43 d i d not pass through t h e narrows. In f a c t , near s t a t i o n A l , e x p e r i m e n t a t i o n showed t h a t a sharp boundary e x i s t e d between t h e water i n a l a r g e back eddy and the water which f l o w e d around A l p h a B l u f f , as shown i n f i g . 22. F i g . 23 i s a l o n g i t u d i n a l s e c t i o n t a k e n i n t h e e a r l y autumn p e r i o d . In c o n t r a s t t o t h e August case ( f i g . 1 7 ) , t h i s s e c t i o n i n d i c a t e s t h a t t h e pycno-c l i n e upstream of s e c t i o n A was s i g n i f i c a n t l y deeper t h a n at A, t h a t i t s depth at s e c t i o n s A and B was about t h e same (as was o b s e r v e d i n the t r a n s v e r s e s e c t i o n s ) , and t h a t i t s depth downstream of s e c t i o n B was s h a l l o w e r t h a n at B. In November, t h e i n t e n s i t y of t h e pycno-c l i n e was f u r t h e r r e d u c e d because of a r e d u c t i o n of f r e s h 3 water p r e s e n t i n t h e s u r f a c e l a y e r ( r u n o f f < 100 m. / s e c ) . I t was c e n t e r e d around 4 t o 6 m., w i t h sigma-t v a l u e s above i t of 15 t o 17. Immediately below the p y c n o c l i n e the v a l u e s of sigma-t s t a y e d r e l a t i v e l y c o n s t a n t at about 19 t o 21 d u r i n g t h e August t o December p e r i o d . T y p i c a l g r a d i e n t s w i t h i n t h e p y c n o c l i n e i n November were 2 sigma-t u n i t s per metre. F i g s . 24 and 25 i l l u s t r a t e t h e approach t o t h e w i n t e r s i t u a t i o n and are t y p i c a l of t h e s e c t i o n s t a k e n on t h i s c r u i s e . Two l o n g i t u d i n a l s e c t i o n s t a k e n i n t h e 4 4 F i g . 22. D e t a i l of f l o w near A l p h a B l u f f . (0815) (0830) (0845) (0900) (0920) (0940) _ l I . I I I I F i g . 23. L o n g i t u d i n a l sigma-t s e c t i o n , 15 September 1967. S t a t i o n p o s i t i o n s i n d i c a t e d a l o n g top w i t h c o r r e s p o n d i n g t i m e s ( P . S . T . ) ; d i s t a n c e (km.) d o w n - i n l e t of s t a t i o n B3 g i v e n a l o n g bottom. Al, (1320) A2 033O) A3 (J345) A4 (1355) A5 (1410) I I I I L_ 0 BI (1505) B2U5 I5 ) B3( I530 ) B4 ( I445 ) B5(I430) _ l I I ! i 101 • 1 F i g . 25. T r a n s v e r s e sigma-t s e c t i o n B, 30 November 1967. S t a t i o n numbers g i v e n a l o n g t o p w i t h c o r r e s p o n d i n g t i m e s ( P . S . T . ) . <1 48 l a t e autumn p e r i o d are shown i n f i g s . 26 and 27. U n l i k e t h e September c a s e s , t h e r e i s no e v i d e n c e i n November of t h e p y c n o c l i n e b e i n g deeper upstream of s e c t i o n A; i f a n y t h i n g i t was s h a l l o w e r t h a n at A. Once a g a i n i t s depth at s e c t i o n A averaged about t h e same as at s e c t i o n B, and i t s depth downstream of B was s h a l l o w e r t h a n at B. As a r e s u l t of a moderate wind b l o w i n g u p - i n l e t f o r s e v e r a l hours b e f o r e t h e measurements were t a k e n i n t h e 29 November case but l i g h t winds i n t h e 1 December c a s e , t h e d e n s i t i e s i n t h e t o p 2 m. i n t h e former s e c t i o n are g r e a t e r t h a n i n the l a t t e r , p r o b a b l y because of a l i m i t e d degree of wave-induced m i x i n g . F u r t h e r m o r e , t h e s t r o n g e r wind appears t o have r e s u l t e d i n a deepening of t h e p y c n o c l i n e upstream of s e c t i o n B, r e l a t i v e t o t h a t c o r r e s p o n d i n g t o t h e l i g h t d o w n - i n l e t wind i n the 1 December ca s e . Other e v i d e n c e ( P i c k a r d and Rodgers, 1959) i n d i c a t e s t h a t a s t r o n g u p - i n l e t w i n d can r e t a r d the o u t f l o w of f r e s h water from a g i v e n r e -g i o n such t h a t t h e i n f l o w i n g f r e s h water i n t o t h e r e g i o n accumulates and the p y c n o c l i n e n o t i c e a b l y deepens. WINTER In t h e m i d - w i n t e r p e r i o d , t h e water down t o at l e a s t 10 m. was e s s e n t i a l l y homogeneous, h a v i n g a sigma-t of about 22. The average g r a d i e n t i n the upper F i g . 26. L o n g i t u d i n a l sigma-t s e c t i o n , 29 November 1967. S t a t i o n p o s i t i o n s i n d i c a t e d a l o n g t o p w i t h c o r r e s p o n d i n g t i m e s ( P . S . T . ) ; d i s t a n c e (km.) d o w n - i n l e t of s t a t i o n B3 g i v e n a l o n g bottom. to F i g . 27. L o n g i t u d i n a l sigma-t s e c t i o n , 1 December 1967. S t a t i o n p o s i t i o n s i n d i c a t e d a l o n g t o p w i t h c o r r e s p o n d i n g t i m e s ( P . S . T . ) ; d i s t a n c e (km.) d o w n - i n l e t o f s t a t i o n B3 g i v e n a l o n g bottom. 51 10 m. was ~ 0 . 1 sigma-t u n i t per metre. A weak pycno-c l i n e appears i n some p r o f i l e s between 4 and 5 m. and i n o t h e r s between 7 and 8 m. , but t h e u n c e r t a i n t i e s are t o o l a r g e r e l a t i v e t o t h e s e v a r i a t i o n s t o j u s t i f y p l o t -t i n g s e c t i o n s and drawing d e f i n i t e c o n c l u s i o n s about th e s l o p e s of d e n s i t y s u r f a c e s and t h e i r average depths. F i g . 28 r e p r e s e n t s t h e same d i r e c t i o n of wind and t i d e as f i g . 16, yet because of t h e s m a l l r u n -o f f i n January ( < 100 m. /sec.) t h e f l o w i s u p - i n l e t , w i t h t h e wind and a g a i n s t the t i d e . However, i t s h o u l d be n o t e d t h a t t h e wind i n t h e January case blew u p - i n l e t at speeds i n e x c e s s of 5 m./sec. f o r more than 12 hours p r e c e d i n g t h e time t h e d r i f t p o l e was s e t o u t , w h i l e i n the August case t h e wind changed from 2 m./sec. down-i n l e t t o i n exc e s s of 5 m./sec. u p - i n l e t o n l y a h a l f hour b e f o r e t h e d r i f t p o l e s were deployed. 52 I i • » • I I J 0 500 1000 2000 S C A L E (M.) F i g . 28. D r i f t p o l e t r a c k f o r 4 January 1968, showing s t a r t i n g t i me (P.S.T.) and average speeds (cm./sec.) f o r each 20 min. i n t e r v a l . 53 DISCUSSION C o n s i d e r i n g the r e s u l t s p r e s e n t e d i n the p r e v i o u s s e c t i o n , i t seems c l e a r t h a t , at l e a s t i n t h i s one r e g i o n of Bute I n l e t , t h e p r i n c i p a l a x i s of the s u r -f a c e l a y e r f l o w c o r r e s p o n d s r o u g h l y w i t h a l i n e down t h e c e n t e r of t h e i n l e t . When th e d o w n - i n l e t s u r f a c e f l o w i s w e l l d e v e l o p e d , e s p e c i a l l y i n t h e summer and e a r l y autumn p e r i o d s , t h e e f f e c t i v e w i d t h of t h e c h a n n e l i s somewhat l e s s t h a n t h e wider s e c t i o n s of t h e i n l e t , such t h a t v e l o c i t i e s were o b s e r v e d t o be s m a l l w i t h i n back e d d i e s near s t a t i o n s A l and A5, but t h e f l o w f i l l e d t he c h a n n e l at s e c t i o n B w i t h o u t back e d d i e s . F i g . 29 i s a s i m p l i f i e d diagram showing a s u r f a c e , seaward f l o w . L o o k i n g at t h e s e c t i o n s i n more d e t a i l , t h e f r e s h water was u s u a l l y c o n c e n t r a t e d t o t h e r i g h t of t h e f l o w d i r e c t i o n at s e c t i o n A but was s p r e a d e v e n l y or c o n c e n t r a t e d t o t h e l e f t of t h e f l o w d i r e c t i o n t h r o u g h s e c t i o n B. In r e g i o n s where t h e c h a n n e l i s s t r a i g h t f o r l o n g s t r e t c h e s , t h e o r y p r e d i c t s t h a t the C o r i o l i s a c c e l e r a -t i o n w i l l cause the f r e s h water t o be c o n c e n t r a t e d t o the r i g h t of t h e d i r e c t i o n of f l o w . Bute I n l e t i s s u f -f i c i e n t l y s i n u o u s i n c h a r a c t e r , however, t h a t at t i m e s t h e c e n t r i p e t a l a c c e l e r a t i o n i n t r o d u c e d by t h e l a t e r a l b o u n d a r i e s was of t h e same o r d e r of magnitude as t h e 54 55 C o r i o l i s a c c e l e r a t i o n l e a d i n g t o t h e p a r t i c u l a r p a t t e r n of f l o w t h r o u g h s e c t i o n B d e s c r i b e d above. V a l u e s of the c e n t r i p e t a l a c c e l e r a t i o n and C o r i o l i s a c c e l e r a t i o n are compared i n t a b l e I I I . The d i r e c t i o n of f l o w of the s u r f a c e l a y e r , e i t h e r u p - i n l e t or d o w n - i n l e t , was det e r m i n e d by t h e r e l a t i v e importance of t h r e e f a c t o r s : f r e s h water r u n -o f f , t h e s t a t e of t h e t i d e , and t h e wind v e l o c i t y . For the peak r u n o f f c a s e s i n summer, t h e s u r f a c e l a y e r a l -ways f l o w e d d o w n - i n l e t w i t h a speed modulated by t h e wind and the t i d e . A s t r o n g u p - i n l e t wind had t h e e f f e c t of s l o w i n g t h e d o w n - i n l e t s u r f a c e f l o w , w h i l e t h e t i d e had r e m a r k a b l y l i t t l e e f f e c t . For the r e d u c e d r u n o f f c a s e s i n autumn, an u p - i n l e t wind was a b l e t o r e v e r s e the s u r f a c e o u t f l o w , i . e . , t h e d i r e c t i o n of t h e s u r f a c e f l o w was b e t t e r r e l a t e d t o t h e wind d i r e c t i o n t h a n t o th e s t a t e of t h e t i d e . For t h e s m a l l r u n o f f c a s e s i n w i n t e r , t h e wind, and i n t h e absence of wind, t h e t i d e , d e t e r m i n e d t h e f l o w d i r e c t i o n . The r u n o f f was e v i d e n t l y t o o s m a l l t o have much n o t i c e a b l e e f f e c t . Appendix I g i v e s e s t i m a t e s of w i n d t r a n s p o r t s based on t h e o b s e r v e d t r a n s p o r t s and t h e c a l c u l a t e d e s t u a r i n e and t i d a l t r a n s -p o r t s ; appendix I I b r i e f l y d i s c u s s e s t h e r e l a t i o n s h i p between f r e s h water r u n o f f and t h e s u r f a c e l a y e r s a l i n i t y TABLE I I I : CENTRIPETAL AND CORIOLIS ACCELERATIONS FOR SECTION B. 15 40 - 2.0 x 1 0 5 - 8 x 1 0 ~ 3 5 x 1 0 ~ 3 - 3 x 1 0 ~ 3 F i g u r e C u r r e n t R a d i u s of C e n t r i p e t a l C o r i o l i s R e s u l t a n t Comments Speed a r c (cm.) A c c e l e r a t i o n A c c e l e r a t i o n A c c e l e r a t i o n (cm./sec.) V 2/R f V V 2/R + f V (cm.sec." 2) ( c m . s e c . - 2 ) ( c m . s e c . - 2 ) 12 60 - 2.0 x 1 0 5 - 18 x 1 0 " 3 7 x 1 0 ~ 3 - 11 x 1 0 ~ 3 F r e s h water p r e -d o m i n a n t l y t o l e f t of f l o w F r e s h water t e n d -i n g t o l e f t . Not as pronounced as i n f i g . 12. 16 25 - 1.7 x 1 0 5 - 4 x 1 0 " 3 3 x 1 0 ~ 3 - 1 x 1 0 " 3 F r e s h water even-l y s p r e a d a c r o s s s e c t i o n . ( S l i g h t tendency, i f any-t h i n g , t o concen-t r a t e t o r i g h t of f l o w . ) 20 50 - 2.9 x 1 0 5 - 9 x 1 0 - 3 6 x 1 0 - 3 - 3 x 1 0 - 3 F r e s h water t o l e f t of f l o w . 21 35 - 2.2 x 1 0 5 - 6 x 1 0 - 3 4 x 1 0 - 3 - 2 x 1 0 - 3 No c o r r e s p o n d i n g d e n s i t y s e c t i o n a v a i l a b l e , Note: P o s i t i v e a c c e l e r a t i o n s are d i r e c t e d t o t h e r i g h t of the f l o w d i r e c t i o n , n e g a t i v e a c c e l e r a t i o n s t o t h e l e f t . C o r i o l i s parameter, f = 1.13 x 10"^ s e c . - J -Ol 57 i n t h e r e g i o n near A l p h a B l u f f . I t s h o u l d be n o t e d t h a t the s e a s o n a l v a r i a -t i o n i n r u n o f f f o r the 1967-68 p e r i o d was somewhat d i f -f e r e n t from t h e l o n g term average, as g i v e n by T r i t e s (1955). In f a c t , r u n o f f f o r 1967-68 was above t h e average d u r i n g June t o September and below th e average d u r i n g October t o January. The o b s e r v a t i o n s of d e n s i t y s t r u c -t u r e and c u r r e n t s r e p o r t e d i n the p r e s e n t paper are not l i k e l y t o d i f f e r q u a l i t a t i v e l y from o b s e r v a t i o n s t a k e n d u r i n g a p e r i o d of more n e a r l y average r u n o f f , w i t h t h e p o s s i b l e e x c e p t i o n of t h e w i n t e r p e r i o d ; q u a n t i t a t i v e l y , however, p y c n o c l i n e i n t e n s i t i e s would l i k e l y be l e s s on t h e average d u r i n g summer and e a r l y autumn. One would have e x p e c t e d some e v i d e n c e of m i x i n g , both by w i n d - i n d u c e d s u r f a c e waves and by t u r -b u l e n c e from shear i n s t a b i l i t i e s , h a v i n g eroded th e pycno-c l i n e from above. Only v e r y l i m i t e d e v i d e n c e of t h i s was found. In t h e August d a t a , o n l y one p o i n t i s a v a i l -a b l e above the p y c n o c l i n e i n most p r o f i l e s . T h i s c o a r s e r e s o l u t i o n r e d u c e s t h e l i k e l i h o o d of o b s e r v i n g d i f f e r e n t degrees of m i x i n g . However, the d a t a from subsequent c r u i s e s c o n t a i n two or more p o i n t s above t h e p y c n o c l i n e i n each p r o f i l e ; n e v e r t h e l e s s o n l y the November c r u i s e c o n t a i n s some i n d i c a t i o n of t h e t y p e of m i x i n g d e s c r i b e d 58 above. The l o n g i t u d i n a l s e c t i o n s produce no e v i -dence of v i g o r o u s or even e s p e c i a l l y s i g n i f i c a n t m i x i n g h a v i n g t a k e n p l a c e i n t h e n e ighborhood of t h e narrows ( s e c t i o n B ) . They do show e v i d e n c e of marked changes i n depth of t h e p y c n o c l i n e a l o n g - i n l e t . Some of t h e s e are r e m a r k a b l y s t e e p , such as 1 t o 2 m. i n 1 km. ( f i g . 2 3 ) . As t h e mean l o n g i t u d i n a l s l o p e of the p y c n o c l i n e from many y e a r s o b s e r v a t i o n s of l o n g i t u d i n a l s e c t i o n s from mouth t o head of the i n l e t i s o n l y of t h e o r d e r of 0.1 m./km., i t i s assumed t h a t t h e s t e e p s l o p e s o b s e r v e d i n some of t h e p r e s e n t l o n g i t u d i n a l s e c t i o n s must be v e r y l i m i t e d i n l o n g i t u d i n a l e x t e n t . The r e a s o n f o r t h e s e s t e e p s l o p e s i s not u n d e r s t o o d , but i t i s p o s s i b l e t h a t t h e y may be i n d i c a t i v e of t h e presence of s h o r t p e r i o d i n t e r n a l waves i n the p y c n o c l i n e , a phenomenon w e l l known i n the B.C. i n l e t s ( P i c k a r d , 1961). A l t h o u g h t h e p r e s e n t s a m p l i n g program was unable t o d e f i n e s t a t i s t i c a l l y such s h o r t time s c a l e p r o c e s s e s as i n t e r n a l waves, some e s t i m a t e of t h e i r pos-s i b l e p e r i o d s can be o b t a i n e d . In t h e summer, the B r u n t -V a i s a l a f r e q u e n c y , d e f i n e d as l 59 where g i s t h e a c c e l e r a t i o n due t o g r a v i t y , p i s t h e d e n s i t y , and Z i s t h e depth ( p o s i t i v e downwards), r a n g e d from ~ 0 . 2 s e c . - ^ around 4 m. t o ~ 0 . 0 4 sec. -"'" around 10 m. depth c o r r e s p o n d i n g t o p e r i o d s of v e r t i c a l o s c i l -l a t i o n of from \ t o 2\ min. V a l u e s f o r t h e w i n t e r r e -gime were not c a l c u l a t e d because of u n c e r t a i n t i e s e x c e s -s i v e l y l a r g e r e l a t i v e t o t h e v a r i a t i o n s i n sigma-t ob-s e r v e d . The r a p i d f l u c t u a t i o n s i n tem p e r a t u r e and s a -l i n i t y o b s e r v e d at some depths but averaged out f o r t h e p r e s e n t a n a l y s i s , and t h e s t e e p s l o p e s of some of t h e i s o p y c n a l s a l o n g - i n l e t , as d e s c r i b e d e a r l i e r , a r e t h e o n l y f i e l d e v i d e n c e which may be a t t r i b u t e d t o i n t e r n a l waves. The r a p i d f l u c t u a t i o n s , of c o u r s e , may have been due t o t u r b u l e n c e o n l y or a c o m b i n a t i o n of t u r b u l e n c e and i n t e r n a l waves. As t h e time t a k e n t o occupy a s t a -t i o n was not l o n g compared t o t h e p r o b a b l e i n t e r n a l wave p e r i o d , t h e o b s e r v a t i o n s may have been i n f l u e n c e d t o some e x t e n t by t h e presence of i n t e r n a l waves. I t i s i m p o s s i b l e w i t h the a v a i l a b l e d a t a t o determine the n a t u r e of t h i s i n f l u e n c e . However, i t i s f e l t t h a t the r e p e a t a -b i l i t y of many of t h e o b s e r v a t i o n s l e n d s support t o t h e a n a l y s i s and r e s u l t s p r e s e n t e d i n t h i s paper. One might ask what e f f e c t i n t e r n a l waves w i t h p e r i o d s of from \ t o l\ min. would have on h y d r o -60 g r a p h i c s t a t i o n p r o f i l e s . In f a c t , the b o t t l e s are a l -lowed t o soak f o r 5 min. b e f o r e a messenger i s dropped and t h e i r f l u s h i n g c h a r a c t e r i s t i c s are such as t o smooth v a r i a t i o n s w i t h p e r i o d s l e s s t h a n 5 min. SUMMARY An i n t e n s e p y c n o c l i n e at about 4 m. depth e x i s t e d i n Bute I n l e t i n August, 1967. T h i s c o r r e s p o n d e d t o t h e l a r g e s t o b s e r v e d f r e s h water r u n o f f i n t o t h e head of t h e i n l e t . The p y c n o c l i n e was g r a d u a l l y weakened t h r o u g h autumn by a r e d u c t i o n i n t h e a v a i l a b l e f r e s h water i n t h e s u r f a c e l a y e r . A major p y c n o c l i n e above 10 m. depth was not o b s e r v e d i n Janu a r y , 1968, c o r r e s p o n d -i n g t o s m a l l f r e s h water r u n o f f . A c e n t r i p e t a l a c c e l e r a t i o n i n t r o d u c e d by the c u r v a t u r e of t h e l a t e r a l b o u n d a r i e s was at t i m e s of s u f f i c i e n t importance t o c o n c e n t r a t e the f r e s h water t o t h e l e f t of t h e f l o w d i r e c t i o n t h r o u g h s e c t i o n B. In summer and e a r l y autumn t h e f l o w was o b s e r v e d t o f i l l s e c t i o n B but not s e c t i o n A such t h a t v e l o c i t i e s were s m a l l w i t h i n back e d d i e s near s t a t i o n s A l and A5. The d i r e c t i o n of f l o w a l o n g - i n l e t was de t e r m i n e d by t h e r e l a t i v e importance of t h r e e f a c t o r s : f r e s h water r u n o f f , t h e s t a t e of t h e t i d e , and t h e wind v e l o c i t y . D u r i n g t h e summer when t h e r u n o f f was l a r g e , a s t r o n g u p - i n l e t w ind had t h e e f f e c t of s l o w i n g but not r e v e r s i n g t h e d o w n - i n l e t s u r f a c e f l o w , w h i l e t h e t i d e had r e m a r k a b l y l i t t l e e f f e c t . D u r i n g autumn, when the r u n o f f was c o n s i d e r a b l y l e s s t h a n t h a t i n summer, 6 2 t h e d i r e c t i o n of the s u r f a c e f l o w was b e t t e r r e l a t e d t o the w i n d d i r e c t i o n t h a n t o t h e s t a t e of t h e t i d e . For th e s m a l l r u n o f f c a s e s i n w i n t e r , t h e wind, and i n the absence of wind, t h e t i d e , d e t e r m i n e d t h e f l o w d i r e c t i o n . Only l i m i t e d e v i d e n c e f o r m i x i n g by wind-i n d u c e d s u r f a c e waves and by t u r b u l e n c e from shear i n -s t a b i l i t i e s , was o b t a i n e d . No s i g n i f i c a n t m i x i n g was o b s e r v e d i n t h e n e i g h b o r h o o d of t h e narrows at s e c t i o n B. Marked l o c a l changes i n t h e depth of the p y c n o c l i n e a l o n g - i n l e t were o b s e r v e d i n September and November, but not i n August. The r e a s o n s f o r t h e s e d i s -t i n c t changes i n depth are not u n d e r s t o o d . 63 SUGGESTIONS FOR FUTURE EXPERIMENTATION I t i s c l e a r t h a t the d e t a i l s of t h e s u r -f a c e f l o w i n even t h i s s m a l l r e g i o n of Bute I n l e t are complex. The p r e s e n t s t u d y has attem p t e d t o determine q u a l i t a t i v e l y some a s p e c t s of t h i s complex f l o w regime. As so o f t e n happens when one b e g i n s t o examine a problem i n some d e t a i l , new problems and ques-t i o n s a re g e n e r a t e d . The p r e s e n t s t u d y i s no e x c e p t i o n ; i n d e e d t h i s was one of t h e u n d e r s t o o d aims of t h e p r o -gram. T y p i c a l q u e s t i o n s t h a t have been r a i s e d a re what p r o c e s s e s a re i n v o l v e d which a f f e c t the o b s e r v e d changes i n depth of t h e p y c n o c l i n e a l o n g t h e a x i s of the i n l e t ? ; how c l o s e l y i s the w i n d c o u p l e d t o t h e s u r f a c e f l o w and what i s the time s c a l e of t h e w a t e r ' s r e s p o n s e t o a v a r i -a b l e wind?; what i n f l u e n c e do t h e l a t e r a l b o u n d a r i e s e x e r t on t h e wind and how im p o r t a n t i s t h i s i n d e t e r m i n i n g t h e d i r e c t i o n of water f l o w ? ; what dete r m i n e s t h e den-s i t y s t r u c t u r e i m m e d i a t e l y below t h e p y c n o c l i n e ? ; why do t h e i s o p y c n a l s sometimes s l o p e down i n the d i r e c t i o n of s t a t i o n A l when t h e d r i f t p o l e s i n d i c a t e t h a t t h e water i s no l o n g e r f l o w i n g out or i s caught i n a back eddy?; what are t h e time s c a l e s a s s o c i a t e d w i t h v a r i a -t i o n s i n c r o s s - c h a n n e l t e m p e r a t u r e and s a l i n i t y g r a d i e n t s and how do t h e s e compare w i t h t h e time t a k e n t o complete 64 a s e c t i o n ? To answer t h e s e q u e s t i o n s and o t h e r s , time s e r i e s t a k e n at one or more s t a t i o n s and a t i g h t e r g r i d of s t a t i o n s i n t h e a r e a of i n t e r e s t u t i l i z i n g a f a s t e r workboat or s e v e r a l b o a t s would be r e q u i r e d . O b s e r v a t i o n s at each s t a t i o n s h o u l d i n c l u d e t h e wind v e l o c i t y as w e l l as s u b s u r f a c e t e m p e r a t u r e s and s a l i n i -t i e s . Dye t r a c e r s c o u l d be used t o p l o t the c u r r e n t s t r u c t u r e i n more d e t a i l and p o s s i b l y o b t a i n b e t t e r e v i -dence f o r t h e degree of m i x i n g , i f any, th r o u g h t h e n a r -row s e c t i o n s of t h e i n l e t . I n f o r m a t i o n on t h e s l o p e of t h e water s u r f a c e from t i d e gauges p l a c e d at t h e f o u r c o r n e r s d e f i n i n g t h e a r e a of i n t e r e s t would be most h e l p -f u l . Some thought s h o u l d be g i v e n t o t h e c h o i c e of a sensor w i t h which t o c a r r y out such a program. An output format s u i t a b l e f o r d i r e c t r e c o r d i n g would be d e s i r a b l e , as s u g g e s t e d e a r l i e r , e s p e c i a l l y i f t h e r e c o r d e d d a t a c o u l d be p r o c e s s e d d i r e c t l y by d i g i t a l computer. The time c o n s t a n t of t h e sensor must be chosen w i t h c a r e . A l o n g time c o n s t a n t w i l l cause t h e i n s t r u -ment t o average out s h o r t time s c a l e p r o c e s s e s . On t h e o t h e r hand, a s h o r t time c o n s t a n t r e q u i r e s a f a s t sam-p l i n g r a t e t o d e f i n e a l l the f r e q u e n c i e s which t h e i n -65 strument w i l l pass. The c h o i c e of i n s t r u m e n t t h e r e f o r e depends e n t i r e l y on t h e p r o c e s s e s which t h e e x p e r i m e n t e r w i s h e s t o i n v e s t i g a t e . To o b t a i n s t a t i s t i c a l l y s i g n i f i -cant d a t a i n the form of s p e c t r a , a f a s t r e s p o n s e i n s t r u -ment would y i e l d t h e most i n f o r m a t i o n . To o b t a i n q u a s i -s y n o p t i c o b s e r v a t i o n s s i m i l a r t o t h o s e o b t a i n e d i n t h e p r e s e n t s t u d y , a slow e r r e s p o n s e i n s t r u m e n t would be p r e f e r a b l e . The s m a l l e s t s c a l e s t r u c t u r e which would t h e n be r e g a r d e d as n o i s e would be averaged out and t h e o b s e r v a t i o n s would become more m e a n i n g f u l i n view of the f i n i t e t i me r e q u i r e d t o sample a g i v e n a r e a . 66 BIBLIOGRAPHY Canada. Dept. of Energy, Mines & R e s o u r c e s . Marine S c i e n c e s Branch. 1967. Canadian t i d e and c u r r e n t t a b l e s , 1968: v. 6, B a r k l e y Sound and D i s c o v e r y Passage t o Dixon E n t r a n c e . Ottawa, Queen's P r i n t e r . Canada. Dept. of Energy, Mines & R e s o u r c e s . I n l a n d Waters Branch. 1968. S u r f a c e water d a t a f o r B r i t i s h Columbia, 1967-8. U n p u b l i s h e d d a t a . Canada. Dept. of Mines & T e c h n i c a l S u r v e y s . Marine S c i e n c e s Branch. 1966. Canadian t i d e and c u r r e n t t a b l e s , 1967: v. 6, B a r k l e y Sound and D i s c o v e r y Passage t o D i x o n E n t r a n c e . Ottawa, Queen's P r i n t e r . P i c k a r d , G.L. 1961. Oceanographic f e a t u r e s of i n l e t s i n the B r i t -i s h Columbia m a i n l a n d c o a s t . J . F i s h . Res. Bd. Canada, _18 ( 6 ) , 907-999. P i c k a r d , G.L. and K. Rodgers. 1959. C u r r e n t measurements i n K n i g h t I n l e t , B r i t -i s h Columbia. J . F i s h . Res. Bd. Canada, _16 ( 5 ) , 635-678. T a b a t a , S. and G.L. P i c k a r d . 1957. The p h y s i c a l oceanography of Bute I n l e t , B r i t i s h Columbia. J . F i s h . Res. Bd. Canada, 14 ( 4 ) , 487-520. T r i t e s , R.W. 1955. A s t u d y of t h e o c e a n o g r a p h i c s t r u c t u r e i n B r i t i s h Columbia i n l e t s and some of t h e d e t e r m i n i n g f a c t o r s . Ph.D. t h e s i s , U n i v e r s i t y of B r i t i s h C o lumbia, Vancouver, B.C. U n i v e r s i t y of B r i t i s h Columbia. I n s t i t u t e of Oceanography. 1968a. Data r e p o r t 27; B r i t i s h Columbia i n l e t c r u i s e s , 1967. Vancouver, B.C. 1968b. U n p u b l i s h e d d a t a . (To be p u b l i s h e d as a d a t a r e p o r t i n 1969.) A P P E N D I C E S APPENDIX I : T r a n s p o r t c a l c u l a t i o n s . E s t i m a t e s of the wind t r a n s p o r t f o r f i v e s e p a r a t e s e t s of d a t a have been d e r i v e d based on t h e o b s e r v e d t r a n s p o r t t h r o u g h s e c t i o n B and c a l c u l a t e d e s -t u a r i n e and t i d a l t r a n s p o r t s . The assumptions and c a l -c u l a t i o n s a re p r e s e n t e d below, u s i n g t h e 16 August case as an example. E s t u a r i n e t r a n s p o r t The average f r e s h water r u n o f f i n t o the 3 head of t h e i n l e t f o r the August c r u i s e was 840 m. /sec. At s e c t i o n B, t h e s u r f a c e s a l i n i t y was 3 o/oo and t h e s a l i n i t y i m m e d i a t e l y below t h e p y c n o c l i n e was 20 o/oo. The volume of f r e s h water f l o w i n g t h rough s e c t i o n B i n one second i s then 840 m. and t h e volume of e n t r a i n e d s a l t water i s V s w . Assuming t h e s o u r c e of t h i s water t o be t h e 20 o/oo water below t h e p y c n o c l i n e , t h e n 8 4 0 + V s w 1000 V s w = | f (840) Of) and V t o t a , = f ^ ( 8 4 0 ) = 9 9 0 m.3 Therefore.,, t h e e s t u a r i n e t r a n s p o r t t h rough s e c t i o n B ( f r e s h water r u n o f f p l u s e n t r a i n e d s a l t water) i s 990 m . / s e c . or about 1.0 x 10 m . / s e c . T i d a l t r a n s p o r t The t i d a l t r a n s p o r t has been c a l c u l a t e d by a l l o w i n g t h e t i d a l p r i s m t o empty or f i l l i n a 6 hour p e r i o d . U s i n g a l e n g t h of 37 km. and an average w i d t h of 3.5 km. f o r the i n l e t from head t o s e c t i o n B, w i t h a t i d a l range of 3.9 m. f o r 16 August, t h e t i d a l p r i s m was 5.1 x 10^ m.3 The t o t a l mean t i d a l t r a n s p o r t was then - 2.3 x 10 m . / s e c , where the n e g a t i v e s i g n i n -d i c a t e s f l o w u p - i n l e t . T h i s t i d a l f l o w has been assumed t o be u n i f o r m over a c r o s s - s e c t i o n of average dimensions. For s i m p l i c i t y , t h i s c r o s s - s e c t i o n has been r e p r e s e n t e d by a t r a p e z o i d whose s u r f a c e and bottom w i d t h s are 3.5 and 3.0 km. r e s p e c t i v e l y and whose depth i s 420 m. The 6 2 a r e a of t h i s c r o s s - s e c t i o n i s t h e n 1.4 x 10 m. S i m i -l a r l y , t h e c r o s s - s e c t i o n a l a r e a of the s u r f a c e l a y e r f o r August was 1.1 x 10^ m.2, s i n c e t h e l a y e r depth was 3 m. T h i s i s 7.8 x 10 ° t i m e s t h e t o t a l c r o s s - s e c t i o n a l a r e a . C o n s e q u e n t l y , w i t h t h e u n i f o r m f l o w assumption, t h e mean s u r f a c e l a y e r t i d a l t r a n s p o r t must have been t h i s same f r a c t i o n of t h e t o t a l mean t r a n s p o r t , namely - 1.8 x 1 0 2 m. 3/sec. 70 Observed t r a n s p o r t The average s u r f a c e l a y e r v e l o c i t y t h r o u g h s e c t i o n B was o b s e r v e d t o be 0.6 m./sec. U s i n g a w i d t h of 1.4 x 1 0 3 m. and a depth of 3 m. f o r t h e s u r f a c e l a y e r at s e c t i o n B, t h e o b s e r v e d t r a n s p o r t t u r n s out t o have been 2.5 x 1 0 3 m. 3/sec. E s t i m a t e d w ind t r a n s p o r t The o b s e r v e d t r a n s p o r t can be r e p r e s e n t e d as a sum of t h e e s t u a r i n e , t i d a l , and wind t r a n s p o r t s , i . e . , T = T e + T t + T w or T w = T - T e - T t = (2.5 - 1.0 + 0.2) x 1 0 3 m. 3/sec. = 1.7 x 1 0 3 m. 3/sec. The wind had been b l o w i n g at speeds of from 4 t o 10 m./sec. d o w n - i n l e t f o r some time p r e c e d i n g t h e o b s e r v a t i o n p e r i o d f o r s e c t i o n B. T h i s l a r g e , down-i n l e t w i nd t r a n s p o r t i s l i k e l y r e l a t e d t o t h i s f a c t . However, the magnitudes of the w ind t r a n s p o r t s which ha\e been c a l c u l a t e d s h o u l d be de-emphasized. They are based on a g r o s s s i m p l i f i c a t i o n of t h e t i d a l f l o w , p r o b a b l y l a r g e u n c e r t a i n t i e s i n t h e average s u r f a c e l a y e r v e l o c i t y ( v a l u e s of v e l o c i t y are from L a g r a n g i a n measurements and no e s t i m a t e s of E u l e r i a n - t y p e s t a n d a r d d e v i a t i o n s are a v a i l a b l e ) , and the use of average r a t h e r t h a n e x a c t dimensions f o r t h e i n l e t . N e v e r t h e l e s s , i n view of t h e s e s i m p l i f i c a t i o n s and u n c e r t a i n t i e s , t h e d i r e c t i o n of t h e e s t i m a t e d wind t r a n s p o r t g e n e r a l l y agrees w i t h t h e average d i r e c t i o n of t h e wind over a few hours p r e c e d i n g t h e o b s e r v a t i o n s of the d e n s i t y s t r u c t u r e and c u r r e n t s at s e c t i o n B. The t r a n s p o r t s f o r the f i v e c a s e s are t a b u l a t e d on the f o l l o w i n g page. OBSERVED AND CALCULATED SURFACE LAYER TRANSPORTS Date Aug. 16 Aug. 17 Aug. 17 Sept. 12 Sept. 14 R e l e v a n t F i g u r e s 11, 12 14, 15 16 none 19, 20 Observed T r a n s p o r t 2.5 2.1 2. 1 n e g l i g i b l e 2.1 E s t u a r i n e T i d a l T r a n s p o r t T r a n s p o r t (x 1 0 3 m. 3/sec.) 1.0 1.0 1.0 0.6 0.6 - 0 . 2 - 0.2 0.1 n e g l i g i b l e - 0.2 Wind T r a n s p o r t 1.7 1.3 1.0 0.6 1 . 7 Comments Wind d o w n - i n l e t (5 t o 10 m./sec.) f o r s e v e r a l hours p r e c e d i n g o b s e r -vat i o n s . V a r i a b l e wind up-i n l e t (1 t o 4 m . / s e c ) ; p r e v i o u s l y d o w n - i n l e t ( a b t . 4 m./sec.) Wind j u s t s t a r t e d u p - i n l e t (7 m . / s e c ) ; p r e v i o u s l y 1 t o 4 m./sec d o w n - i n l e t . Wind u p - i n l e t ( a b t . 2 m./sec.); p r e -v i o u s l y d o w n - i n l e t ( a b t . 3 m./sec.) f o r few hours. Wind d o w n - i n l e t (abt. 9 m./sec.) f o r s e v e r a l hours p r e -c e d i n g o b s e r v a t i o n s . to APPENDIX I I : R e l a t i o n between f r e s h water r u n o f f and s u r f a c e l a y e r s a l i n i t y . The average f r e s h water r u n o f f f o r each c r u i s e and t h e c o r r e s p o n d i n g average s u r f a c e l a y e r s a l i n i t y have been p l o t t e d i n t h e f i g u r e on t h e f o l l o w i n g page. I t i s a s t r o n g l y n o n - l i n e a r r e l a t i o n s h i p . Indeed some degree of n o n - l i n e a r i t y would be e x p e c t e d . D u r i n g p e r i o d s of h i g h r u n o f f the d e n s i t y s t r a t i f i c a t i o n i s i n t e n s e and t e n d s t o l i m i t m i x i n g p r o c e s s e s . D u r i n g low r u n o f f , t h e s t r a t i f i c a t i o n i s g r e a t l y r e d u c e d a l l o w -i n g more v i g o r o u s m i x i n g . One would expect t h a t t h e r e s u l t would be -to b r i n g even more s a l i n e water upwards t h a n a l i n e a r r e l a t i o n t o r u n o f f would p r e d i c t . The d a t a appear t o support t h i s h y p o t h e s i s . 74 32 T 28 (SALINITY AT -{ABOUT 50 m. JDEPTH fUPPER LIMIT TO • < RUNOFF; GAUGE NOT [.FUNCTIONING PROPERLY 24 2 0 — \ 2I6 |— _i < to 12 -8 1 I 2 0 0 4 0 0 600 8 0 0 DISCHARGE (M. 3 /SEC.) 1000 1200 P l o t o f ave rage s u r f a c e l a y e r s a l i n i t y as a f u n c t i o n o f ave rage f r e s h wa te r r u n o f f . 

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