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Temperature microstructure in Howe Sound Bilodeau, Laurent Ernest 1979

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TEMPERATURE MICROSTRUCTURE IN HOWE SOUND by LAURENT ERNEST BILODEAU B. A. Sc. Laval University, 1972 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE i n THE FACULTY OF GRADUATE STUDIES i n the Department of Physics and the I n s t i t u t e of Oceanography We accept t h i s thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA SEPTEMBER 1978 Laurent Ernest Bilodeau, 1978 In p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l m e n t o f t h e r e q u i r e m e n t s f o r a n a d v a n c e d d e g r e e a t t h e 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 t h e L i b r a r y s h a l l m a k e 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 a n d 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 t h e H e a d o f my D e p a r t m e n t o r by h i s r e p r e s e n t a t i v e s . I t i s u n d e r s t o o d t h a t c o p y i n g o r 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 n o t 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 . D e p a r t m e n t o f 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 2075 W e s b r o o k P l a c e V a n c o u v e r , C a n a d a V6T 1WS D a t e 12 QMtA A b s t r a c t Temperature m i c r o s t r u c t u r e o b s e r v a t i o n s o b t a i n e d i n Howe Sound a r e p r e s e n t e d and r e l a t e d t o t h e i r o c e a n o g r a p h i c c o n t e x t , I n some i n s t a n c e s , two f r e e - f a l l i n g p r o b e s have been l a u n c h e d s i m u l -t a n e o u s l y w i t h s e p a r a t i o n s o f 10 t o 20 m a t t h e s u r f a c e i n an a t t e m p t to l o o k a t t h e l a t e r a l e x t e n t o f t e m p e r a t u r e m i c r o s t r u c t u r e f e a t u r e s . P a t c h e s o f t e m p e r a t u r e g r a d i e n t v a r i a n c e were found where t h e g r a d i e n t p r e s e n t e d peak v a l u e s o f b o t h s i g n s a t s m a l l e r s c a l e s . These p a t c h e s were u s u a l l y o b s e r v e d by one probe o n l y and seem t o e x t e n d l a t -e r a l l y o v e r l e s s t h a n 20 m. I n o t h e r i n s t a n c e s t h e peak g r a d i e n t v a l u e s t o o k m o s t l y t h e same s i g n w i t h i n a g i v e n p a t c h . Such p a t c h e s were u s u a l l y d e t e c t e d by b o t h p r o b e s , i n d i c a t i n g t h a t t h e i r h o r i z o n t a l e x t e n t i s s i g n i f -i c a n t l y l a r g e r t h a n 20 m. These t y p e s o f t e m p e r a t u r e m i c r o s t r u c t u r e a r e a l s o d i s c u s s e d i n terms o f mechanisms t h a t c o u l d p r o v i d e an e x p l a n a t i o n f o r t h e i r e x i s t e n c e . I n Howe Sound's I n n e r B a s i n , t h e Deep Water o c c a s i o n a l l y r e c e i v e s l a r g e i n f l u x e s o f w a t e r from t h e S t r a i t o f G e o r g i a . O t h e r w i s e , i t s t a y s e s s e n t i a l l y t r a p p e d b e h i n d a 75 m deep s i l l and becomes more homogeneous w i t h t i m e . A model i s p r e s e n t e d w h i c h r e l a t e s t h e r a t e a t w h i c h t e m p e r a t u r e becomes homogeneous t o t e m p e r a t u r e g r a d i e n t v a r i a n c e and t he m o l e c u l a r c o e f f i c i e n t o f h e a t d i f f u s i o n . O t h e r p a r t s o f t h e wa t e r column a r e d i s c u s s e d i n terms o f t h e Osborn-Cox (1972) model o f v e r t i c a l h e a t t r a n s p o r t . i i i T a b l e o f c o n t e n t s Page A b s t r a c t i i T a b l e o f c o n t e n t s i i i L i s t o f t a b l e s v i L i s t o f f i g u r e s v i i Acknowledgments x i C h a p t e r I : I n t r o d u c t i o n 1 1.1 G e n e r a l i n t r o d u c t i o n 1 1.2 Howe Sound: geography, t i d e s , w i nds and r i v e r d i s c h a r g e 2 1.3 E a r l i e r i n v e s t i g a t i o n o f t h e p h y s i c a l oceanography o f Howe Sound 4 Ch a p t e r I I : New a s p e c t s o f t h e o c e a n o g r a p h i c and c u r r e n t meter d a t a 10 I I . 1 The I n t e r m e d i a t e Water . 10 I I . 2 The Deep Water r e n e w a l i n t h e F a l l o f 1973 . . 13 Ch a p t e r I I I : M i c r o s t r u c t u r e methods and d a t a p r o c e s s i n g . . 17 I I I . l P r o b e s and r e s o l u t i o n 17 I I I . 2 Method o f d a t a p r o c e s s i n g 19 I I I . 3 Summary of the d a t a 21 i v Page Chapter IV: Temperature structure of Howe Sound i n November 1973 and February 1974 . . . . 24 IV.1 Temperature structure i n November 1973 . . . 24 IV.2 Temperature structure i n February 1974 . . . 27 a) Recent evolution of water properties i n Howe Sound 27 b) Temperature structure i n the Outer Basin . . 28 c) Temperature structure i n the Inner Basin's Intermediate Water 30 d) Temperature structure i n the Inner Basin's Deep Water 32 IV. 3 Discussion a) An Intermediate Water c i r c u l a t i o n pattern? . . 34 b) The Osborn-Cox model 35 c) A model for an i s o l a t e d and inhomogeneous volume of f l u i d 41 Chapter V: Detailed aspect of temperature microstructure . 44 V. l Introduction 44 V.2 Detailed p r o f i l e s 45 a) November 1973 p r o f i l e s 45 b) Outer Basin, February 1974 . 47 c) Inner Basin Intermediate Water (February 1974) 50 d) Inner Basin Deep Water (February 1974) . . . 57 Page V.3 D i s c u s s i o n a) Summary of m i c r o s t r u c t u r e d e s c r i p t i o n . . . 59 b) R e l a t i o n s h i p between t e m p e r a t u r e and t e m p e r a t u r e g r a d i e n t m i c r o s t r u c t u r e . . . . 60 c) L a t e r a l e x t e n t o f m i c r o s t r u c t u r e 62 d) T u r b u l e n t o r n o t ? 64 e) D o u b l y - d i f f u s i v e o r n o t ? 67 C h a p t e r V I : C o n c l u s i o n 70 R e f e r e n c e s 72 T a b l e s 75 F i g u r e s 78 L i s t o f T a b l e s L i s t o f t h e l o c a t i o n s and t i m e s a t w h i c h d o u b l e drops were made d u r i n g the F e b r u a r y 1974 m i c r o -s t r u c t u r e c r u i s e , t o g e t h e r w i t h t h e s e p a r a t i o n of t h e p r o b e s a t l a u n c h and r e c o v e r y . L i s t o f t h e l o c a t i o n s and t i m e s a t w h i c h s i n g l e d rops were made d u r i n g t h e November 1973 m i c r o -s t r u c t u r e c r u i s e , t o g e t h e r w i t h t h e v a l u e s o b s e r v e d f o r t h e mean sq u a r e v e r t i c a l t e m p e r a t u r e g r a d i e n t . Mean square v a l u e s o f t h e v e r t i c a l t e m p e r a t u r e g r a d i e n t and n e t t e m p e r a t u r e change o b s e r v e d a c r o s s t h e I n t e r m e d i a t e Water d u r i n g t h e F e b r u a r y 1974 m i c r o s t r u c t u r e c r u i s e . v i i L i s t o f F i g u r e s F i g . 1 C h a r t o f Howe Sound. F i g . 2 L o n g i t u d i n a l s e c t i o n o f Howe Sound and c r o s s c h a n n e l s e c t i o n s made a t the s i l l and a t s t a t i o n Howe 4. F i g . 3 T y p i c a l w i n t e r p r o f i l e s o f t e m p e r a t u r e and s a l i n i t y i n t h e Out e r B a s i n and i n t h e I n n e r B a s i n o f Howe Sound. F i g . 4 Time s e r i e s o f t e m p e r a t u r e o b s e r v a t i o n s o b t a i n e d i n t h e Outer B a s i n a t dept h s o f 100 m and more. F i g . 5 Time s e r i e s o f t e m p e r a t u r e and s a l i n i t y o b s e r v a t i o n s o b t a i n e d between 20 and 75 m i n b o t h b a s i n s o f Howe Sound. F i g . 6 Time s e r i e s o f o b s e r v a t i o n s o f (a) t e m p e r a t u r e , (b) s a l i n i t y , (c) s i g m a - t and (d) d i s s o l v e d oxygen a t dept h s o f 100 m and more a t s t a t i o n Howe 4 ( I n n e r B a s i n ) . F i g . 7 L o n g i t u d i n a l s e c t i o n o f Howe Sound showing t h e l o c a t i o n o f the I n t e r m e d i a t e Water and of t h e Deep Water. F i g . 8 D i s t r i b u t i o n o f t e m p e r a t u r e , s a l i n i t y and d i s s o l v e d oxygen a l o n g t h e c e n t e r o f t h e I n n e r B a s i n on September 20, 1973. F i g . 9 D i s t r i b u t i o n o f T, S and D.0. a l o n g t h e c e n t e r o f t h e I n n e r B a s i n on November 13, 1973. F i g . 10 D i s t r i b u t i o n o f T, S and D.0. a l o n g the c e n t e r o f t h e I n n e r B a s i n on J a n u a r y 22, 1974. F i g . 11 Time s e r i e s o f t e m p e r a t u r e and N-S c u r r e n t v e l o c i t y o b t a i n e d a t s t a t i o n Howe 4 a t a de p t h o f 150 m by an Aanderaa c u r r e n t meter between O c t o b e r 3 and November 15, 1973. v i i i F i g . 12 D e s c r i p t i o n o f a "Pumpkin" m i c r o s t r u c t u r e p r o f i l e r and of i t s t e m p e r a t u r e s e n s i n g element. F i g . 13 L o c a t i o n o f t h e m i c r o s t r u c t u r e p r o f i l e s o b t a i n e d i n Howe Sound i n November 1973. F i g . 14 O v e r a l l p r o f i l e o f Drop P-10. F i g . 15 O v e r a l l p r o f i l e o f Drop P - l l . F i g . 16 O v e r a l l p r o f i l e o f Drop P-12. F i g . 17 O v e r a l l p r o f i l e o f Drop P-13. F i g . 18 O v e r a l l p r o f i l e o f Drop P-14. F i g . 19 O v e r a l l p r o f i l e o f Drop P-15. F i g . 20 O v e r a l l p r o f i l e o f Drop P-16. F i g . 21 D e t a i l e d segment from Drop P-12. F i g . 22 D e t a i l e d segment from Drop P-12. F i g . 23 D e t a i l e d segment f r o m Drop P-13. F i g . 24 D e t a i l e d segment from Drop P-13. F i g . 25 STD l o n g c h a n n e l s e c t i o n made on November 22, 1974 i n t h e I n n e r B a s i n o f Howe Sound. F i g . 26 STD c r o s s c h a n n e l s e c t i o n made on November 22, 1974 a t s t a t i o n Howe 4. F i g . 27 STD c r o s s c h a n n e l s e c t i o n made on November 22, 1974 a t s t a t i o n Howe 4.7. F i g . 28 L o c a t i o n o f t h e m i c r o s t r u c t u r e p r o f i l e s o b t a i n e d i n Howe Sound i n F e b r u a r y 1974. F i g . 29 O v e r a l l p r o f i l e o f Drop 6. F i g . 30 O v e r a l l p r o f i l e o f Drop 7. F i g . 31 O v e r a l l p r o f i l e o f Drop 8. i x F i g . 32 O v e r a l l p r o f i l e of Drop 9. F i g . 33 O v e r a l l p r o f i l e of Drop 10. F i g . 34 Deep part of Drop 7 with an expanded temperature scale. F i g . 35 Deep part of Drop 8 with an expanded temperature scale. F i g . 36 Deep part of Drop 9 with an expanded temperature scale. F i g . 37 Deep part of Drop 10 with an expanded temperature scale. F i g . 38 Comparison between STD p r o f i l e s made on January 22 and February 4, 1974, i n both Howe Sound's basins. Fi g . 39 STD long channel section made on February 6, 1974 i n Howe Sound's Inner Basin. F i g . 40 STD cross channel section made at s t a t i o n Howe 4 on February 6, 1974. F i g . 41 Detailed p r o f i l e from Drop 6. F i g . 42 Detailed p r o f i l e from Drop 6. F i g . 43 Detailed p r o f i l e from Drop 6. F i g . 44 Detailed p r o f i l e from Drop 7. F i g . 45 Detailed p r o f i l e from Drop 7. F i g . 46 Detailed p r o f i l e from Drop 7. F i g . 47 Detailed p r o f i l e from Drop 8. F i g . 48 Detailed p r o f i l e from Drop 8. F i g . 49 Detailed p r o f i l e from Drop 9. F i g . 50 Detailed p r o f i l e from Drop 9. F i g . 51 Detailed p r o f i l e from Drop 9. F i g . 52 Detailed p r o f i l e from Drop 10. F i g . 53 Detailed p r o f i l e from Drop 10. X F i g . 54 D e t a i l e d p r o f i l e F i g . 55 D e t a i l e d p r o f i l e F i g . 56 D e t a i l e d p r o f i l e F i g . 57 D e t a i l e d p r o f i l e f r o m Drop 1 0 . from t h e Deep Water of Drop 7. from t h e Deep Water of Drop 7. f r o m t h e Deep Water of Drop 8. Acknowledgments I am g r e a t l y i n d e b t e d t o Dr Thomas Osborn f o r h i s s u p p o r t and a d v i c e t h r o u g h a l l phases o f t h e work w h i c h l e a d t o t h e c o m p l e t i o n o f t h i s t h e s i s . H i s e x p e r i e n c e , f i n a n c i a l h e l p , p a t i e n c e and o c c a s i o n a l l a c k o f i t were a l l i n v a l u a b l e . I would a l s o l i k e t o t h a n k Dr P a u l L e b l o n d f o r h i s d e t a i l e d and p o s i t i v e c r i t i c i s m o f t h e e a r l y and f i n a l d r a f t s o f t h i s t h e s i s , and Dr G. L. P i c k a r d and Dr R. W. B u r l i n g f o r v e r y a p p r o p r i a t e comments about t h e e a r l y d r a f t . 1 C h a p t e r I I n t r o d u c t i o n 1.1 G e n e r a l I n t r o d u c t i o n . The purpose o f t h i s t h e s i s i s t o p r e s e n t t e m p e r a t u r e m i c r o -s t r u c t u r e and f i n e s t r u c t u r e o b s e r v a t i o n s w h i c h were o b t a i n e d i n Howe Sound i n November 1973 and F e b r u a r y 1974, and t o i n v e s t i g a t e some o f t h e i r s i g n i f i c a n c e . The term " m i c r o s t r u c t u r e " a p p l i e s t o t h e d i s t r i b u t i o n o f o c e a n o g r a p h i c p r o p e r t i e s a t s c a l e s s m a l l e r t h a n one me t r e . O b s e r v a -t i o n s r e p o r t e d by Gregg e t a l . (1973) i n an o c e a n i c environment show t h a t most o f t h e v a r i a n c e o f t h e t e m p e r a t u r e g r a d i e n t i s found a t s c a l e s s m a l l e r t h a n 0.1 m. I n t h e d i s t r i b u t i o n o f s p e c t r a l d e n s i t i e s o f t he t e m p e r a t u r e g r a d i e n t , Gregg e t a l . found a s p e c t r a l minimum n e a r s c a l e s o f i m. G a r g e t t (1976) used t h i s t o d e f i n e " f i n e s t r u c t u r e " as a p p l y i n g t o s c a l e s l a r g e r t h a n a m e t r e , up t o t e n s o f m e t r e s . G a r g e t t ' s d e f i n i t i o n i s r e t a i n e d f o r t h i s t h e s i s and, c o n s e q u e n t l y , " m i c r o s t r u c t u r e " w i l l a p p l y h e r e t o s c a l e s s m a l l e r t h a n one m e t r e . L i t t l e i s known about t h e o c c u r r e n c e and t h e r o l e o f temper-a t u r e m i c r o s t r u c t u r e i n f j o r d s and i n l e t s . D r i n k w a t e r (1973) used t e m p e r a t u r e m i c r o s t r u c t u r e o b s e r v a t i o n s i n a s t u d y o f t h e r o l e o f t i d a l m i x i n g i n R u p e r t and H o l b e r g I n l e t s t o d e t e c t t h e o c c u r r e n c e o f 2 t u r b u l e n t s t i r r i n g . He found t h a t t u r b u l e n t s t i r r i n g o c c u r r e d i n a s s o c i a t i o n w i t h t i d a l c u r r e n t s and, n e a r t h e s u r f a c e , w i t h s u r f a c e w i n d s . He t r a c e d a mid-depth i n t r u s i o n i n t o H o l b e r g I n l e t and o b s e r v e d l e s s t e m p e r a t u r e m i c r o s t r u c t u r e away from the mouth of t h e i n l e t . No o t h e r p u b l i s h e d s t u d y d e s c r i b e d o r used t e m p e r a t u r e m i c r o s t r u c t u r e o b s e r v a t i o n s o b t a i n e d i n i n l e t s . Howe Sound was chosen f o r t h i s s t u d y because i t i s easy o f a c c e s s and because i t has been the f o c u s o f s e v e r a l i n v e s t i g a t i o n s w h i c h have p r o v i d e d much back g r o u n d i n f o r m a t i o n about i t s oceanography f o r t h e p e r i o d o f 1971 t o 1974. 1.2 Howe Sound: geography, t i d e s , w i n d , r i v e r d i s c h a r g e . Howe Sound i s a f j o r d i n l e t l o c a t e d 30 km N o r t h West o f Vanc o u v e r , on t h e m a i n l a n d c o a s t o f the S t r a i t o f G e o r g i a (see f i g . 1 ) . I t c o n s i s t s o f two b a s i n s s e p a r a t e d by a s i l l w i t h a maximum d e p t h o f 70 m (see f i g . 1 ) . The Outer B a s i n ( a l s o c a l l e d S o u t h B a s i n ) f e a t u r e s a number of i s l a n d s and p a s s a g e s . The southernmost p a s s a g e , t h e Queen C h a r l o t t e C h a n n e l , i s about 250 m deep a l o n g i t s e n t i r e l e n g t h . The I n n e r B a s i n ( a l s o c a l l e d N o r t h B a s i n ) has a maximum d e p t h o f 290 m and a mean w i d t h o f about 3 km. The s i l l i s l o c a t e d 28 km from t h e mouth o f Howe Sound and 17 km from t h e head. A c r o s s c h a n n e l p r o f i l e of t h e s i l l i s p r e s e n t e d i n f i g . 2. 3 P o i n t A t k i n s o n i s the c l o s e s t t i d a l r e f e r e n c e p o i n t t o Howe Sound. A t P o i n t A t k i n s o n , the a m p l i t u d e r a t i o o f t h e f o u r main c o n s t i -t u e n t s i s : K.l + °1 _ 2.810 + 1.555 _ . M 2 + S 2 2.979 + 0.748 D e f a n t (1961, p.307) d e s c r i b e s such a v a l u e o f t h e r a t i o as a mixed, m a i n l y s e m i - d i u r n a l t y p e . The t i d a l range a t Squamish (head o f Howe Sound) i s s m a l l e r t h a n t h a t o f P o i n t A t k i n s o n (mouth o f Howe Sound) by a few c e n t i m e t r e s w h i l e t h e phases l a g b e h i n d t h o s e o f P o i n t A t k i n s o n by a few m i n u t e s ( C a n a d i a n H y d r o g r a p h i c S e r v i c e , 1977). Thus t h e P o i n t A t k i n s o n t i d a l p r e d i c t i o n s can be used a c c u r a t e l y i n Howe Sound. The mean t i d a l range a t Squamish i s 3.1 m ( C a n a d i a n Hydro-g r a p h i c S e r v i c e , 1977). F o r t h e purpose o f a s i m p l e t i d a l p r i s m model, th e mean de p t h o f t h e s i l l i s about 45 m. I f t h e f l o w were u n i f o r m o v e r t h e s i l l and i f t h e t i d e was p u r e l y s e m i - d i u r n a l , t h e mean t i d a l r ange would g i v e r i s e t o peak v e l o c i t i e s o f 8.5cm/sec. B u c k l e y (1977) r e p o r t s a c a l c u l a t i o n w h i c h s u g g e s t s t h a t b a r o c l i n i c t i d e s have a s m a l l e r b u t n o t n e g l i g i b l e e f f e c t . The A t m o s p h e r i c E n v i r o n m e n t S e r v i c e o p e r a t e s an anemometer w h i c h i s l o c a t e d i n t h e c e n t e r o f t h e v a l l e y , c l o s e t o t h e w a t e r , on the s i t e o f FMC o f Canada L t d . ( f i g . 1 ) , n e a r Squamish. The anemometer r e c o r d s the h o u r l y wind r u n and d i r e c t i o n i n o c t a n t s . Because o f t h e s t e e p mountains w h i c h l i n e t he v a l l e y , t h e w i n d blows o n l y seldom from t h e E a s t o f the West. D o w n - i n l e t w i n d s dominate d u r i n g w i n t e r ( O c t o b e r t o March) and u p - i n l e t w i nds dominate d u r i n g t h e summer ( A p r i l t o A u g u s t ) . A more d e t a i l e d s t u d y o f t h e h o u r l y w i n d r e c o r d s r e v e a l s t h a t t h e r e a r e p e r i o d s when the d i u r n a l w i n d c y c l e a c c o u n t s f o r most of t h e v a r i a n c e i n t h e wi n d p a t t e r n s . A t o t h e r t i m e s , i t i s the e f f e c t o f l a r g e r weather systems w h i c h p r e d o m i n a t e s w i t h p e r i o d s o f l i g h t o r s t r o n g w inds l a s t i n g from one t o f o u r days. The Squamish R i v e r c o n s t i t u t e s t h e main f r e s h w a t e r t r i b u t a r y o f t h e i n l e t . H o u r l y d i s c h a r g e measurements a r e t a k e n a t the D a i s y Lake Dam a t B r a c k e n d a l e , 25 km n o r t h o f Squamish (Water Survey o f 3 Canada s t a t i o n 8GA22). The r i v e r d i s c h a r g e i s t y p i c a l l y 100 m / s e c 3 i n w i n t e r (November t o A p r i l ) and t y p i c a l l y .3.00 m / s e c i n summer (May t o September). The d a i l y d i s c h a r g e can be e x p e c t e d t o peak o c c a s i o n a l l y a t s e v e r a l t i m e s t h e s e v a l u e s . The h i g h e s t d a i l y d i s c h a r g 3 o f t h e y e a r 1973 o c c u r r e d on O c t o b e r 28 w i t h a mean r a t e o f 1170 m /sec I.3 E a r l i e r i n v e s t i g a t i o n s o f Howe Sound's P h y s i c a l Oceanography. Many i n v e s t i g a t o r s have v i s i t e d Howe Sound. B u c k l e y (1977) g i v e s a d e t a i l e d l i s t g o i n g back t o C a p t a i n Vancouver. I n t h i s s t u d y , r e f e r e n c e i s made o n l y t o r e c e n t i n v e s t i g a t i o n s w h i c h c o v e r e d b o t h b a s i n s and the e n t i r e w a t e r column, c o n t i n u o u s l y o r on a m o n t h l y b a s i s . I n 1968, t h e M a r i n e S c i e n c e s B r a n c h o f the Department o f t h e Environ m e n t o f Canada c a r r i e d a program o f o b s e r v a t i o n o f t h e S t r a i t o f G e o r g i a w h i c h r e s u l t e d i n mon t h l y c r u i s e s i n Howe Sound ( C r e a n and Ages, 1971). The I n s t i t u t e o f Oceanography has c a r r i e d o u t a program 5 of m o n t h l y c r u i s e s i n Howe Sound between September 1971 and March 1974 and t h e d a t a a r e a v a i l a b l e i n D a t a R e p o r t s ( I.O.U.B.C., 1972, e t c . ) The C o a s t a l Oceanography Group o f the I n s t i t u t e o f Ocean S c i e n c e a t P a t r i c i a Bay has o p e r a t e d c h a i n s o f c u r r e n t m e t e r s i n b o t h b a s i n s o f Howe Sound. A s t a t i o n c l o s e t o Howe 4 was o c c u p i e d between November 1972 and F e b r u a r y 1974. The de p t h s w h i c h were m o n i t o r e d were: 3 m (Geodyne A-850 v e c t o r a v e r a g i n g c u r r e n t m e t e r ) , 5, 10, 15, 20, 30 and 150 m (Aanderaa RCM-4 c u r r e n t m e t e r s ) . The r e s u l t i n g d a t a have been p u b l i s h e d by B e l l (1975) under t h e form o f h i s t o g r a m s and p r o g r e s -s i v e v e c t o r d i a g r a m s . These d a t a have been a n a l y z e d by B e l l (1973) and P i c k a r d (1975) f r o m t h e p o i n t o f v i e w o f t h e e v o l u t i o n o f t h e Deep Water p r o p -e r t i e s and by B u c k l e y (1977) f o r t h e c u r r e n t meter d a t a . B u c k l e y (1977) a l s o c a r r i e d o ut an e x p e r i m e n t w i t h r a d a r - t r a c k e d drogues t o s t u d y t h e dynamics o f t h e S u r f a c e L a y e r . T y p i c a l w i n t e r p r o f i l e s o f t e m p e r a t u r e and s a l i n i t y i n Howe Sound a r e p r e s e n t e d i n f i g u r e 3. They were o b t a i n e d a t s t a t i o n s Howe 3 (O u t e r B a s i n ) and Howe 4 ( I n n e r B a s i n ) on F e b r u a r y 5 and 6, 1974. The p r o f i l e s i l l u s t r a t e t h a t t h e d e n s i t y o f t h e Howe Sound wa t e r i s c o n t r o l l e d by s a l i n i t y w h i c h i n c r e a s e s w i t h d e p t h . I n f i g . 3, te m p e r a t u r e i n c r e a s e s w i t h depth so t h a t i t s e f f e c t p a r t l y c o u n t e r a c t s t h a t o f s a l i n i t y . A t o t h e r t i m e s o f t h e y e a r , t e m p e r a t u r e may d e c r e a s e w i t h d e p t h o v e r p a r t o f t h e w a t e r column b u t i t p l a y s a s e c o n d a r y r o l e i n d e t e r m i n i n g t h e d e n s i t y o f t h e Howe Sound w a t e r . 6 F i g u r e 3 a l s o shows t h a t t e m p e r a t u r e and s a l i n i t y a r e v e r y homogeneous b e l o w 100 m i n the I n n e r B a s i n compared t o what i s f o u n d a t s i m i l a r d e p t h i n t h e Ou t e r B a s i n and compared t o what i s fo u n d i n b o t h b a s i n s above 100 m. P i c k a r d (1975) has i n d i c a t e d t h a t a m a j o r i t y o f t h e i n l e t s o f the B r i t i s h C o l umbia m a i n l a n d c o a s t show y e a r l y v a r i a t i o n s i n t h e i r Deep Water p r o p e r t i e s . These changes appear t o o c c u r t h r o u g h a d v e c t i v e p r o c e s s e s i n v o l v i n g w a t e r from t h e S t r a i t o f G e o r g i a . I n t h e Deep Water o f a few i n l e t s , s u c h y e a r l y v a r i a t i o n s a r e n o t a p p a r e n t ; the Deep Water t h e r e may r e m a i n t r a p p e d f o r more t h a n a y e a r a t a t i m e . Howe Sound appears t o c o n s t i t u t e a b o r d e r l i n e c a s e , presumably because o f i t s s h a l l o w s i l l . P i c k a r d (1975) d e s c r i b e s the e v o l u t i o n o f the Deep Water a t 200 m, a t s t a t i o n Howe 4, as p r e s e n t i n g a saw t o o t h p a t t e r n . Q u i c k changes o c c u r i n t h e s a l i n i t y , t e m p e r a t u r e and d i s s o l v e d oxygen. They a r e f o l l o w e d by s l o w changes w h i c h a r e a t t r i b u t e d t o non-a d v e c t i v e p r o c e s s e s such as t u r b u l e n t t r a n s f e r and b i o c h e m i c a l p r o c e s s e s ( f o r d i s s o l v e d o x y g e n ) . P i c k a r d (1975) i n d i c a t e d t h a t i t was n o t c l e a r w hether t h e Deep Water i n Howe Sound underwent a n n u a l changes o r more i n t e r m i t t e n t ones. B e l l (1973) s t u d i e d Deep Water r e p l a c e m e n t s i n t h e I n n e r B a s i n . He examined p r i n c i p a l l y t he e v o l u t i o n o f t h e d i s s o l v e d oxygen concen-t r a t i o n (D.O.) and s a l i n i t y a t d e p t h s o f 100, 150 and 200 m. I n a wa t e r volume such as t h e Deep Water o f t h e I n n e r B a s i n w h i c h i s i s o l a t e d f rom s u r f a c e exchanges and s u n l i g h t , D.O. v a l u e s a r e e x p e c t e d t o d e c r e a s e w i t h t i m e under t h e i n f l u e n c e of l o c a l b i o c h e m i c a l p r o c e s s e s . 7 S i m i l a r l y , s a l i n i t y i s e x p e c t e d t o d e c r e a s e w i t h t i m e because some f r e s h e r w a t e r from above g e t s t u r b u l e n t l y mixed i n t o t h e Deep Water. B e l l argued t h a t whenever D.0. and s a l i n i t y i n t h e I n n e r B a s i n ' s Deep Water showed s i g n i f i c a n t d e p a r t u r e s from t h e i r downward t r e n d s , some w a t e r from t h e O u t e r B a s i n had found i t s way i n t o t h e I n n e r B a s i n ' s Deep Water. He f o u n d a t the 100 m l e v e l , i n f l o w s appeared t o o c c u r f r e q u e n t l y , a l l y e a r round. A t t h e 150 and 200 m l e v e l s , m ajor i n -f l o w s appeared t o o c c u r a t l e a s t e v e r y few y e a r s . The volume and the d e p t h o f p e n e t r a t i o n o f the i n f l o w s appear v a r i a b l e . B e l l (1973) s u g g e s t e d t h a t t h e s e i n f l o w s were t r i g g e r e d by h i g h r i v e r run o f f and s t r o n g seaward winds ("Squamish w i n d s " ) . A p r e l i m i n a r y c o n d i t i o n f o r t h i s , o f c o u r s e , i s t h a t the o u t s i d e w a t e r found n e a r the s i l l l e v e l has t o be as dense a s , o r d e n s e r t h a n t h e Deep Water o f t h e I n n e r B a s i n . These c o n d i t i o n s a r e most l i k e l y t o be met i n e a r l y w i n t e r . D u r i n g June and J u l y 1973, B u c k l e y (1977) s t u d i e d t h e S u r f a c e L a y e r o f Howe Sound w i t h n e a r s u r f a c e p r o f i l e s o f t e m p e r a t u r e and s a l i -n i t y and w i t h r a d a r t r a c k e d s u r f a c e drogues. He f o u n d t h a t t h e d e p t h o f t h e h a l o c l i n e v a r i e d between 0 and 5 m d u r i n g h i s e x p e r i m e n t . The h a l o c l i n e was s h a r p e s t n e a r t h e mouth o f the r i v e r and more d i f f u s e f u r t h e r away. I t s depth v a r i e d w i t h t i m e , l o n g i t u d i n a l and l a t e r a l p o s i t i o n s . The b u l k o f B u c k l e y ' s e x p e r i m e n t was made w i t h drogues w i t h s a i l s s e t between 0 and 2 m. He found t h a t t h e r i v e r d i s c h a r g e f o l l o w e d a meandering p a t t e r n o v e r t h e i n l e t . D u r i n g a s h o r t e x p e r i m e n t , 8 B u c k l e y used drogues w i t h s a i l s s e t a t d i f f e r e n t d e p t h s . He fo u n d b o t h an o u t f l o w and a s t r o n g r e t u r n f l o w w i t h t h e i r c o r e s i n t h e upper 5 m. The c o r e s were l o c a t e d on d i f f e r e n t s i d e s o f the i n l e t . B u c k l e y t h e n examined the n e a r s u r f a c e c u r r e n t meter r e c o r d s and found t h a t a t 3 m, the c u r r e n t was on aver a g e g o i n g down i n l e t a t 3.6 cm/sec w h i l e a t 5 m, i t was on aver a g e g o i n g up i n l e t a t 4.2 cm/sec and a t 10 m, t h e r e were l a r g e f l u c t u a t i o n s c e n t e r e d n e a r z e r o v e l o c i t y . B u c k l e y f ound t h a t n e a r t h e head o f t h e i n l e t , w i n d s , t i d e s and v a r i a t i o n s i n t h e r i v e r d i s c h a r g e a c c o u n t e d f o r v a r i a t i o n s i n the v e l o c i t y f i e l d w h i c h had comparable m a g n i t u d e s . F u r t h e r down the i n l e t , i t was the wind w h i c h dominated the c i r c u l a t i o n o f the S u r f a c e L a y e r . The c u r r e n t meter s t r i n g e s t a b l i s h e d by the P a c i f i c Oceano-g r a p h i c Group i n t h e I n n e r B a s i n o f Howe Sound had 6 mete r s l o c a t e d i n the upper 30 m and o n l y one meter below t h i s , a t 150 m. The s p e c t r a l v a r i a n c e o f t h e c u r r e n t r e c o r d s was c o n c e n t r a t e d i n t h e band o f one t o two c y c l e s p e r day ( B u c k l e y , 1977). B u c k l e y showed t h a t a t i d a l p r i s m 2 2 model y i e l d e d a r a t i o o f t h e d i u r n a l v e l o c i t y v a r i a n c e (m /sec ) t o the s e m i - d i u r n a l v a r i a n c e o f 0.31. The c u r r e n t meter a t 150 m y i e l d e d a r a t i o o f 0.30. The o t h e r c u r r e n t m e t e r s , l o c a t e d i n the upper 30 m, had r a t i o s w h i c h were q u i t e v a r i a b l e b u t alw a y s l a r g e r t h a n 0.7. By e x a m i n i n g the shape o f t h e s p e c t r a , B u c k l e y c o n c l u d e d t h a t t h e e f f e c t o f w inds d e c r e a s e d w i t h depth and became i n s i g n i f i c a n t a t 150 m. Winds o v e r Howe Sound have a s t r o n g d i u r n a l component w h i c h would e x p l a i n why t h e r a t i o o f d i u r n a l t o s e m i - d i u r n a l v a r i a n c e i s l a r g e r n e a r the s u r f a c e . 9 The c u r r e n t meter l o c a t e d a t 150 m r e c o r d e d r o u t i n e l y v e l o c i -t i e s o f 0.15 m/sec. I n t h e c u r r e n t v e c t o r diagrams p r e s e n t e d by B e l l ( 1 9 7 3 ) , d u r i n g November and December 1973, t h e r e was a c o n s i s t e n t r e s i d u a l c u r r e n t o f the o r d e r o f .01 m/sec ( r o u g h l y 1 km/day) f l o w i n g towards t h e s i l l . D u r i n g J a n u a r y and F e b r u a r y 1974, no such c o n s i s t e n t d r i f t was f o u n d . N o t i c e t h a t t h e c u r r e n t meter i s l o c a t e d 80 m below maximum s i l l d e p t h . I t i s n o t c l e a r whether t h e r e s i d u a l c u r r e n t i s r e a l o r whether i t i s an a r t i f a c t o f t h e c u r r e n t meter and i t s m o o r i n g . 10 C h a p t e r I I New A s p e c t s o f t h e Oc e a n o g r a p h i c and C u r r e n t M e t e r D a t a . B e l l ( 1 9 7 3 ) , P i c k a r d (1975) and B u c k l e y (1977) have been c o n c e r n e d m o s t l y w i t h t h e Deep Water (below s i l l d e p t h , i n t h e I n n e r B a s i n ) and the S u r f a c e L a y e r o f Howe Sound. However, much of t h e te m p e r a t u r e m i c r o s t r u c t u r e i n f o r m a t i o n w h i c h has been o b t a i n e d i n Howe Sound comes fr o m t h e d e p t h range o f 10 t o 100 m. Moreover, much o f the d a t a were o b t a i n e d i n November 1973 e i t h e r d u r i n g o r s h o r t l y a f t e r a Deep Water r e n e w a l . B o t h t h e 10 t o 100 m d e p t h range and t h e Deep Water r e n e w a l o f the f a l l o f 1973 have r e c e i v e d l i t t l e a t t e n t i o n e a r l i e r . T h i s c h a p t e r p r e s e n t s and d i s c u s s e s some d a t a r e l e v a n t t o t h e s e a s p e c t s o f t h e p h y s i c a l oceanography o f Howe Sound. I I . 1 The I n t e r m e d i a t e Water. The o b j e c t o f t h i s s e c t i o n i s t o show b r i e f l y t h a t t h e r e a r e r e g i o n s i n Howe Sound where the e v o l u t i o n o f o c e a n o g r a p h i c p r o p e r t i e s i s c o n t r o l l e d m a i n l y by h o r i z o n t a l exchanges between t h e S t r a i t o f G e o r g i a , the Ou t e r B a s i n and the I n n e r B a s i n . F o r t h e pu r p o s e o f t h i s s t u d y , t h e w a t e r found i n t h e s e r e g i o n s i s c a l l e d t h e " I n t e r m e d i a t e Water". The d a t a p r e s e n t e d h e r e come from t h e m o n t h l y o c e a n o g r a p h i c c r u i s e s made by the I n s t i t u t e o f Oceanography o f t h e 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 between 1972 and 1974 (I.O.U.B.C., 1972, e t c . ) . F i g u r e 4 shows the t e m p e r a t u r e t i m e - s e r i e s o b s e r v e d a t 100 m and below a t s t a t i o n s Howe 2 and Howe 3 i n t h e Ou t e r B a s i n . F i g u r e 5 p r e s e n t s t i m e s e r i e s o f t e m p e r a t u r e and s a l i n i t y f r o m each b a s i n a v e r -aged between 20 and 75 m. The s t a t i o n s a r e Howe 3 (O u t e r B a s i n ) and Howe 4.5 ( I n n e r B a s i n ) (see f i g . 1 ) . The samples from 20, 30, 50 and 75 m were a v e r a g e d w i t h w e i g h t s o f 2, 3, 4, 4 t o r e f l e c t t he s i z e o f the depth i n t e r v a l r e p r e s e n t e d by each v a l u e . F i g u r e 6 p r e s e n t s t h e t i m e - s e r i e s o f t e m p e r a t u r e , s a l i n i t y , s i g m a - t and d i s s o l v e d oxygen o b t a i n e d a t 100 m and below i n t h e I n n e r B a s i n (Howe 4.5). F i g u r e 4 shows l a r g e v a r i a t i o n s o f t e m p e r a t u r e on a t i m e s c a l e w h i c h i s w e l l r e s o l v e d by t h e m o n t h l y r a t e o f s a m p l i n g . The v a r i a t i o n s a r e a r e f l e c t i o n o f . t h o s e t a k i n g p l a c e i n the S t r a i t o f G e o r g i a ( P i c k a r d , 1975) and i l l u s t r a t e t h e r e l a t i v e l y f r e e exchanges t a k i n g p l a c e between the S t r a i t o f G e o r g i a and t h e Ou t e r B a s i n , m a i n l y t h r o u g h t h e Queen C h a r l o t t e C h a n n e l . I n f i g u r e 5, the t e m p e r a t u r e t i m e - s e r i e s show t h a t t h e v a r i a -t i o n s w h i c h o c c u r between 20 and 75 m i n b o t h b a s i n s f o l l o w a p a t t e r n s i m i l a r t o t h a t w h i c h i s o b s e r v e d below 100 m i n t h e O u t e r B a s i n . The range o f t h e t e m p e r a t u r e v a r i a t i o n s a t Howe 4.5 ( I n n e r B a s i n ) i s s l i g h t l y s m a l l e r t h a n t h a t a t Howe 3 (Outer B a s i n ) b u t no s i g n i f i c a n t l a g i s o b s e r v e d between the two t i m e - s e r i e s . The two s a l i n i t y t i m e -s e r i e s o f f i g . 5 a l s o t r a c k each o t h e r q u i t e c l o s e l y . I n s e v e r a l i n s t a n c e s , l a r g e changes i n s a l i n i t y a r e o b s e r v e d i n b o t h b a s i n s by t h e same c r u i s e s and t h u s t h e y may o c c u r w i t h i n a t i m e i n t e r v a l s h o r t e r t h a n one month. Only i n f l o w s o f s a l i n e w a t e r may r e s u l t i n i n c r e a s e s i n s a l i n i t y and, i n Howe Sound, o n l y t h e S t r a i t o f G e o r g i a may p r o v i d e t h i s s a l i n e w a t e r . Thus t h e v a r i a t i o n s i n s a l i n i t y and t e m p e r a t u r e o b s e r v e d above 75 m i n b o t h b a s i n s r e s u l t f r o m exchanges w i t h t h e S t r a i t o f G e o r g i a w h i c h can t a k e p l a c e on a time s c a l e s m a l l e r t h a n one month. I n f i g u r e 6, t h e t i m e - s e r i e s o f t e m p e r a t u r e , s a l i n i t y , s i g m a - t and d i s s o l v e d oxygen a t 125 m and below show p e r i o d s of s t e a d y t r e n d s e p a r a t e d by p e r i o d s o f l a r g e r and more a b r u p t change. T h i s p a t t e r n i s d e s c r i b e d as " s a w - t o o t h " by P i c k a r d ( 1 9 7 5 ) . B e l l (1973) showed t h a t i t c o r r e s p o n d s t o p e r i o d s when d i f f u s i v e p r o c e s s e s dominate and t o p e r i o d s when t h e r e a r e i n f l o w s f r o m t h e O u t e r B a s i n , o v e r t h e s i l l and i n t o t h e I n n e r B a s i n ' s Deep Water. T h i s p a t t e r n d i f f e r s m a r k e d l y from t h e one w h i c h was o b s e r v e d i n f i g . 4 and 5, f o r t h e O u t e r B a s i n and t h e p a r t of t h e I n n e r B a s i n a t 75 m and above. The p r e c e d i n g d i s c u s s i o n shows t h a t the I n t e r m e d i a t e Water, as d e f i n e d i n t h e f i r s t p a r a g r a p h o f t h i s s e c t i o n , i s found between about 20 m and t h e bottom i n t h e O u t e r B a s i n . I n t h e I n n e r B a s i n , i t i s chosen t o p u t t h e l o w e r l i m i t o f t h e I n t e r m e d i a t e Water a t 100 m s i n c e i n f i g . 6, t h e w a t e r a t 100 m had an e v o l u t i o n m a r k e d l y d i f f e r e n t from t h e w a t e r a t 125 m and below. The w a t e r a t 125 m and below i n the I n n e r B a s i n i s t h e r e f o r e c a l l e d the "Deep Water" i n t h i s t h e s i s . Near t h e s u r f a c e , i t i s n o t c l e a r a t what d e p t h exchanges w i t h the S t r a i t o f G e o r g i a become l e s s i m p o r t a n t t h a n t h e v e r t i c a l t u r b u l e n t t r a n s f e r o f t h e l o c a l f r e s h w a t e r r u n o f f . B u c k l e y showed t h a t , i n June 1973, most o f the f r e s h w a t e r was f o u n d i n t h e upper 10 m. Thus t h e upper l i m i t o f t h e I n t e r m e d i a t e Water may be s e t a t 10 m below t h e s u r f a c e f o r t h e purpose o f t h i s s t u d y . F i g u r e 7 p r e s e n t s a l o n g - c h a n n e l s e c t i o n o f Howe Sound where t h e S u r f a c e L a y e r , the I n t e r m e d i a t e Water and t h e Deep Water a r e shown. I I . 2 A Deep Water r e n e w a l i n the F a l l o f 1973. I n t he F a l l o f 1973, a Deep Water r e n e w a l o c c u r r e d i n the I n n e r B a s i n o f Howe Sound. On November 20 and 21, 1973 a c r u i s e made te m p e r a t u r e m i c r o s t r u c t u r e o b s e r v a t i o n s i n t h e I n n e r B a s i n . The i n t e r p r e t a t i o n o f the r e s u l t i n g d a t a ( p r e s e n t e d i n t h e n e x t c h a p t e r s ) r e q u i r e s t h a t some o f t h e i n f o r m a t i o n a v a i l a b l e f o r t h e Deep Water r e n e w a l be examined f i r s t . F i g u r e s 8, 9 and 10 p r e s e n t l o n g - c h a n n e l s e c t i o n s o f temper-a t u r e , s a l i n i t y and d i s s o l v e d oxygen (D.0.) o b t a i n e d w i t h b o t t l e c a s t s on September 20, 1973, on November 13, 1973 and on J a n u a r y 22, 1974 (I.O.U.B.C., 1973). F i g u r e 11 p r e s e n t s t h e t e m p e r a t u r e r e c o r d and the N-S component o f the v e l o c i t y r e c o r d o b t a i n e d a t 150 m by a c u r r e n t meter c h a i n l o c a t e d n e a r s t a t i o n Howe 4, f o r the p e r i o d o f O c t o b e r 25 t o November 15. P o s i t i v e c u r r e n t v a l u e s i n f i g . 11 i n d i c a t e a n o r t h -ward f l o w . N o r t h l i e s a p p r o x i m a t e l y i n an u p - i n l e t d i r e c t i o n ( f i g . l ) . The Deep Water d i s t r i b u t i o n o f September 20, 1973 ( f i g . 9 ) i s t y p i c a l o f t h a t w h i c h was e n c o u n t e r e d d u r i n g the p r e v i o u s s i x months (I.O.U.B.C., 1973). I t i s i n t e r e s t i n g t o n o t i c e t h a t the l o w e s t D.O. v a l u e s a r e f o u n d a l o n g t h e bottom p r o f i l e r a t h e r t h a n any o t h e r i s o -p l e t h . A l s o , a l o n g a same d e p t h l e v e l , c o n t r a s t s o f up t o 0.09 C° and 0.009 °/oo a r e f o u n d i n t h e b o t t l e c a s t d a t a ( I.O.U.B.C, 1973). They a r e of o p p o s i n g s i g n and no m e a s u r a b l e d e n s i t y d i f f e r e n c e r e s u l t s from them. A t e m p e r a t u r e minimum i s f o u n d a t 100 m ( f i g . 8 ) . The m o n t h l y c r u i s e s show t h a t t h e t e m p e r a t u r e a t 100 m has s t a y e d i n the v i c i n i t y o f 7.9 t o 8.0 °C s i n c e t h e p r e v i o u s June w h i l e t h e temp-e r a t u r e a t 75 m changed from c o o l e r t o warmer th a n t h i s ( I . O . U . B . C , 1973). A t 125 m and b e l o w , the t i m e - s e r i e s i n d i c a t e t h a t no l a r g e or a b r u p t change i n p r o p e r t y has o c c u r r e d (see f i g . 6 ) s i n c e the p r e v i o u s F e b r u a r y . The November 13, 1973 Deep Water d i s t r i b u t i o n ( f i g . 9 ) d i f f e r s m a r k e d l y from t h a t o f September. The I n n e r B a s i n i s now o c c u p i e d by two d i s t i n c t w a t e r masses. One mass o c c u p i e s the d e p t h range of 50 t o 200 m i n the u p - i n l e t p a r t o f t h e b a s i n . I t has the same o c e a n o g r a p h i c p r o p e r t i e s as the w a t e r w h i c h was p r e v i o u s l y f ound i n the d e e p e s t p a r t s o f the I n n e r B a s i n ( c o l d e r t h a n 8.3 C, l e s s s a l i n e t h a n 30.5 /oo and w i t h D.O. c o n c e n t r a t i o n s s m a l l e r t h a n 2.5 m l / 1 ) . T h i s w a t e r i s now c a l l e d t h e " O l d Water". The o t h e r w a t e r mass i s f o u n d below 200 m and above 50 m t h r o u g h the I n n e r B a s i n . A t Howe 4, towards t h e s i l l and i n the O u t e r B a s i n , i t o c c u p i e s t h e whole w a t e r column ( I.O.U.B.C, 1973). I t s p r o p e r t i e s a r e d i s t i n c t l y d i f f e r e n t from t h o s e o f the O l d Water and i t i s now c a l l e d the "New Water" ( t e m p e r a t u r e h i g h e r t h a n 8.5 °C, s a l i n i t y h i g h e r t h a n 30.5 °/oo, D.O. c o n c e n t r a t i o n h i g h e r t h a n 2.4 m l / 1 ) . The s i g m a - t v a l u e of b o t h w a t e r masses i s between 3 23.67 and 23.70 kg/m and t h e d e n s i t y s t r a t i f i c a t i o n b e l o w 100 m i s too s m a l l t o be a c c u r a t e l y e s t i m a t e d . The J a n u a r y 22, 1974 Deep Water d i s t r i b u t i o n ( f i g . 1 0 ) s t i l l p r e s e n t s two d i s t i n c t w a t e r masses. T h i s shows p a r t i c u l a r l y w e l l i n t h e D.O. d i s t r i b u t i o n . The c o n t r a s t between t h e two w a t e r masses i s s m a l l e r t h a n i n November ( f i g . 9 ) . The t e m p e r a t u r e d i f f e r e n c e between th e two c o r e s has d e c r e a s e d f r o m 0.5 C° t o 0.3 C° and t h e s a l i n i t y d i f f e r e n c e has d e c r e a s e d from 0.10 °/oo t o 0.08 °/oo. A t d e p t h s o f 100 m and l e s s , t h e s a l i n i t y v a l u e s a r e l o w e r t h a n i n J a n u a r y and t h e D.O. v a l u e s a r e h i g h e r , i n d i c a t i n g t h a t exchanges have been c o n t i n u i n g a t t h a t l e v e l . I n the c u r r e n t meter c h a i n l o c a t e d n e a r s t a t i o n Howe 4 d u r i n g t h e Deep Water r e n e w a l , t h e 150 m c u r r e n t meter was t h e o n l y one i n s t a l l e d below 30 m. B u c k l e y (1977) , u s i n g o n l y t h e v e l o c i t y r e c o r d o f t h i s m eter, deduced t h a t t h e Deep Water i n f l o w t o o k p l a c e e s s e n t i a l l y between November 9 and 13. D u r i n g t h i s p e r i o d , t h e p r o -g r e s s i v e v e c t o r diagrams ( B e l l , 1975) show a n e t u p - i n l e t c u r r e n t i n s t e a d o f t h e u s u a l d o w n - i n l e t " d r i f t " w h i c h was m entioned e a r l i e r i n t h i s c h a p t e r . F i g . 11 p r e s e n t s t h e N-S component o f t h e c u r r e n t v e l o c i t y and t h e t e m p e r a t u r e r e c o r d o b t a i n e d f r o m t h e c u r r e n t meter l o c a t e d a t 150 m. F i g u r e 11 shows t h a t , s t a r t i n g O c t o b e r 27, t h e r e a r e warm w a t e r " p u l s e s " o c c u r r i n g once a day a t 150 m u n t i l O c t o b e r 31. The o n l y p o s s i b l e s o u r c e of w a t e r warmer t h a n 8.4 C i s c l e a r l y New Water coming from t h e Outer B a s i n ( f i g . 8 and 9 ) . Thus, f i g . 11 shows t h a t the Deep Water r e n e w a l s t a r t e d b e f o r e o r on O c t o b e r 27. I t i s n o t c l e a r whether t h e warm w a t e r was a d v e c t e d h o r i z o n t a l l y o r v e r t i c a l l y p a s t t h e c u r r e n t meter and no e s t i m a t e o f t h e volume of t h e i n f l o w can be made from t h e c u r r e n t meter r e c o r d s a l o n e . S t a r t i n g November 2, t h e 150 m c u r r e n t meter becomes predom-i n a n t l y immersed i n warm w a t e r . The c u r r e n t v e l o c i t y shows l a r g e r v a r i a t i o n s t h a n p r e v i o u s l y and o f t e n p r e s e n t s a s o r t o f " s q u a r e wave" p a t t e r n . The r e a s o n s f o r t h i s a r e n o t c l e a r . One can s p e c u l a t e t h a t f u r t h e r i n f l o w s a r e o c c u r r i n g a t t h a t t i m e , b u t one can a l s o s p e c u -l a t e t h a t t h e Deep Water i s r e s p o n d i n g t o a c h a n g i n g p a t t e r n of f o r c i n g f u n c t i o n s ( s u r f a c e w i n d s , t i d e s , r i v e r r u n o f f ) and t h a t the 150 m c u r r e n t meter has become immerged p r e d o m i n a n t l y i n New Water as a r e s u l t o f t h i s r a t h e r t h a n as a r e s u l t o f new i n f l o w s . I n summary, the o c e a n o g r a p h i c t i m e - s e r i e s show t h a t a Deep Water r e n e w a l o c c u r r e d between September and November 1973. The c u r r e n t meter t e m p e r a t u r e r e c o r d a t 150 m i n d i c a t e s t h a t t h e r e n e w a l had a t l e a s t s t a r t e d on O c t o b e r 27. The c u r r e n t meter v e l o c i t y r e c o r d i s of l i t t l e use. The New Water o c c u p i e s t h e l o w e r 200 m o f th e Deep Water and, n e a r t h e c e n t e r o f t h e c h a n n e l , t h e p a r t o f t h e I n n e r B a s i n l o c a t e d between Howe 4 and t h e s i l l . Some of the temper-a t u r e m i c r o s t r u c t u r e d a t a w h i c h a r e p r e s e n t e d i n t h e f o l l o w i n g c h a p t e r s were o b t a i n e d s h o r t l y a f t e r November 18, 1973. I t i s now c l e a r t h a t t h e s e d a t a were o b t a i n e d a f t e r t h e b u l k o f t h e Deep Water r e n e w a l had t a k e n p l a c e . C h a p t e r I I I M i c r o s t r u c t u r e methods and d a t a p r o c e s s i n g . I I I . l P r o b e s and r e s o l u t i o n . I n t h e c o u r s e o f p r e v i o u s work i n m i c r o s t r u c t u r e , t h e need has o f t e n been f e l t f o r a s e t o f l i g h t , s i m p l e and rugged t e m p e r a t u r e m i c r o s t r u c t u r e p r o f i l e r s . The f i r s t m o t i v a t i o n i n u s i n g s u c h p r o b e s was t o i n v e s t i g a t e t h e h o r i z o n t a l c h a r a c t e r i s t i c s o f t e m p e r a t u r e m i c r o s t r u c t u r e by making s i m u l t a n e o u s p r o f i l e s . T h i s was d i f f i c u l t t o do w i t h e a r l i e r o r more complex i n s t r u m e n t s . The d e s i g n of l i g h t t e m p e r a t u r e m i c r o s t r u c t u r e p r o f i l e r s was i n i t i a t e d i n 1972 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 and r e s u l t e d i n a s e t o f t h r e e i d e n t i c a l p r obes nicknamed "Pumpkin" f o r t h e orange s p h e r i c a l f l o a t s w h i c h p r o v i d e s t h e i r buoyancy. The p r o b e s a r e d e s c r i b e d i n d e t a i l i n Osborn (1977). A s c h e m a t i c d r a w i n g o f one i s shown i n f i g . 12. The probes p r o v i d e a s u p p o r t f o r a t h e r m i s t o r b r i d g e and i t s e l e c t r o n i c s . The t h e r m i s t o r i s a m e t a l oxyde m i c r o b e a d w i t h a t y p i c a l d i a m e t e r of 150 m i c r o n s , c o a t e d w i t h a f i l m o f P a r a l e n e - C w i t h a t h i c k n e s s o f about 15 m i c r o n s f o r e l e c t r i c a l i n s u l a t i o n ( f i g . 1 2 ) To r e d u c e the o c c u r r e n c e of e l e c t r i c a l l e a k s i n t o sea w a t e r , t h e t h e r m i s t o r s u p p o r t arms ( n o t the m i c r o b e a d s ) were c o a t e d w i t h g l y p t o l . The f r e q u e n c y r e s p o n s e o f such a t h e r m i s t o r moving i n a f l u i d has been s t u d i e d by Lueck, Hertzman and Osborn ( 1 9 7 7 ) . F o r a t y p i c a l v e l o c i t y o f 20 cm/sec, t h e i r c a l c u l a t i o n s i n d i c a t e the 3 dB p o i n t i n s p a t i a l r e s o l u t i o n t o be c l o s e t o 2 cm. The p r e s e n t s t u d y c o n s i s t s o f an i n v e s t i g a t i o n o f t h e t y p e s o f f i n e s t r u c t u r e and m i c r o s t r u c t u r e f e a t u r e s e n c o u n t e r e d i n Howe Sound and o f t h e i r h o r i z o n t a l v a r i a b i l i t y . The a n a l y s i s o f the d a t a i s n o t based on q u a n t i t a t i v e e s t i m a t e s o f the t o t a l v a r i a n c e o f t h e v e r t i c a l t e m p e r a t u r e g r a d i e n t . T h e r e f o r e , t h e i n d i v i d u a l f r e q u e n c y r e s p o n s e o f each t h e r m i s t o r was n o t measured and no a t t e m p t has been made t o c o r r e c t t h e h i g h f r e q u e n c y r o l l - o f f . The t h e r m i s t o r was p a r t o f a Wheatstone b r i d g e . The e l e c t r o -n i c package o f t h e probe g e n e r a t e d a t e m p e r a t u r e s i g n a l and t h e time d e r i v a t i v e o f t h i s s i g n a l . These were r e l a y e d t o t h e s u r f a c e t h r o u g h a S i p p i c a n XWL (Exp e n d a b l e W i r e L i n k ) u s i n g IRIG FM c h a n n e l s . A t the s u r f a c e , t h e s e s i g n a l s were r e c o r d e d on tape t o be l a t e r p l a y e d back and d i g i t i z e d a t a r a t e of 250 samples p e r second p e r c h a n n e l . F o r a t y p i c a l s i n k i n g r a t e o f 20 cm/sec, t h i s c o r r e s p o n d s t o 12.5 samples p e r cm. The n o i s e p r e s e n t i n t h e s i g n a l s has been e s t i m a t e d from t h e deep p a r t s o f t h e p r o f i l e s where no m e a n i n g f u l s i g n a l c o u l d be d e t e c t e d . Most o f the n o i s e v a r i a n c e was i n t h e h i g h e r f r e q u e n c y range o f t h e i n s t r u m e n t , a t wave numbers h i g h e r t h a n 2 cm A t dept h s g r e a t e r t h a n 100 m, i t i n c r e a s e d a p p r e c i a b l y w i t h d e p t h because o f t h e i n c r e a -s i n g l e n g t h o f the XWL l i n k . Near 150 m, t y p i c a l rms n o i s e v a l u e s a r e : 0.01 C° i n t h e t e m p e r a t u r e c h a n n e l and 0.03 C°/m i n t h e g r a d i e n t c h a n n e l . D u r i n g the F e b r u a r y 1974 c r u i s e , the m i c r o s t r u c t u r e p r o b e s were used i n p a i r s . They were r e l e a s e d w i t h a h o r i z o n t a l s e p a r a t i o n o f 3, 10 and 20 m. They f e l l f r e e l y t o a de p t h o f 150 t o 200 m b e f o r e r e l e a s i n g some b a l l a s t w e i g h t and f l o a t i n g b ack t o the s u r f a c e . The p r o b e s s u r f a c e d w i t h s e p a r a t i o n s between 1 and 75 m. The s p a c i n g of t h e p r o b e s a t r e c o v e r y d i d n o t c o r r e l a t e w i t h the s p a c i n g a t l a u n c h (see T a b l e I ) . D u r i n g t h e d e s c e n t , t h e probes p r o b a b l y s t a y e d w i t h i n 3 t o 40 m of each o t h e r and t h e y r e a c h e d the de p t h o f 100 m w i t h i n one m i n u t e o f each o t h e r . I I I . 2 Method o f d a t a p r o c e s s i n g . The f i r s t s t e p i n p r o c e s s i n g the d i g i t i z e d d a t a was t o con-s t r u c t rough v e r t i c a l t e m p e r a t u r e p r o f i l e s by p l o t t i n g t h e tempera-t u r e s i g n a l v e r s u s t i m e . These p r o f i l e s were t h e n compared w i t h p r o -f i l e s o f t e m p e r a t u r e v e r s u s d e p t h o b t a i n e d a t the same l o c a t i o n w i t h a B i s s e t t - B e r m a n 9060 s e l f - c o n t a i n e d STD r e c o r d e r . S a l i e n t f e a t u r e s o f t h e p r o f i l e s were matched and t h e i r d e p t h s and t e m p e r a t u r e s on the STD c h a r t were n o t e d . By assuming t h e Pumpkin s i n k i n g r a t e t o be c o n s t a n t , the matched f e a t u r e s p r o v i d e d a d e p t h s c a l e w i t h an a c c u r a c y o f ± 3 m (± 5 %•).' When t h e Pumpkins had been used i n p a i r s , t h e a n a l y s i s r e q u i r e d y e t a f i n e r match of t h e de p t h s c a l e s so t h a t f e a t u r e s s m a l l e r t h a n s e v e r a l metres c o u l d be p a i r e d w i t h o u t a m b i g u i t y . F o r t h i s , two s a l i e n t f e a t u r e s o f one p r o f i l e were a s s i g n e d the same depth s as the e q u i v a l e n t f e a t u r e s on the o t h e r p r o f i l e o f t h e p a i r and t h e de p t h s c a l e was r e c o n s t r u c t e d by l i n e a r i n t e r p o l a t i o n . The r e s i s t a n c e o f t h e t h e r m i s t o r s d e c r e a s e s a p p r o x i m a t e l y e x p o n e n t i a l l y when t e m p e r a t u r e i n c r e a s e s . The e x p o n e n t i a l c o e f f i -c i e n t o f t h i s r e s p o n s e was known and i t was used t o g e t h e r w i t h t h e matched f e a t u r e s o f t h e STD p r o f i l e t o c o n s t r u c t a t e m p e r a t u r e c a l i -b r a t i o n w i t h an a c c u r a c y o f + 0.3 C° i n t h e range o f 6 t o 9 °C. The g a i n o f t h e d i f f e r e n t i a t o r c i r c u i t was checked by com-p a r i n g i t s s i g n a l w i t h t h e t e m p e r a t u r e s i g n a l . Then t h e t e m p e r a t u r e c a l i b r a t i o n , t h e d i f f e r e n t i a t o r c i r c u i t g a i n and t h e e s t i m a t e d s i n k -i n g r a t e were used t o s c a l e t h e d i f f e r e n t i a t e d t e m p e r a t u r e s i g n a l i n t o a v e r t i c a l t e m p e r a t u r e g r a d i e n t (°C/m) w i t h an a c c u r a c y o f + 10%. O v e r a l l p r o f i l e s : F o r c o n s t r u c t i n g o v e r a l l p r o f i l e s o f each d r o p , t h e d i g i -t i z e d t e m p e r a t u r e and g r a d i e n t d a t a were grouped i n b l o c k s o f 512 p o i n t s p e r c h a n n e l . Each b l o c k c o n t a i n e d i n f o r m a t i o n f r o m about 0.4 m o f t h e w a t e r column. F o r each b l o c k , a mean t e m p e r a t u r e , a mean t e m p e r a t u r e g r a d i e n t and a rms t e m p e r a t u r e g r a d i e n t were c a l c u -l a t e d . Each o v e r a l l p r o f i l e c o n s i s t s o f up t o 550 of t h e s e v a l u e s p l o t t e d w i t h t h e de p t h s c a l e o b t a i n e d i n t h e p r e v i o u s l y d e s c r i b e d f a s h i o n . Examples o f such p r o f i l e s a r e found i n f i g u r e s 14 t o 20. - D e t a i l e d p r o f i l e s : I t was a l s o p o s s i b l e t o p l o t t h e o r i g i n a l d i g i t i z e d s i g n a l o f t e m p e r a t u r e and g r a d i e n t s c a l e d i n °C and °C/m u s i n g t h e same c a l -i b r a t i o n method as f o r t h e o v e r a l l p r o f i l e . However, i n t h i s c a s e , b e f o r e u s i n g t h e c a l i b r a t i o n , the g r a d i e n t s i g n a l was i n t e g r a t e d i n t o a s y n t h e t i c t e m p e r a t u r e s i g n a l . T h i s was compared w i t h t h e o r i g i n a l t e m p e r a t u r e s i g n a l and t h e e f f e c t o f t h e g r a d i e n t o f f s e t was removed. Then, the new t e m p e r a t u r e s i g n a l and the g r a d i e n t s i g n a l were s c a l e d u s i n g the c a l i b r a t i o n . The s i g n a l was t h e n p l o t t e d w i t h s c a l e s o f 5 t o 1 m p e r i n c h . By t h i s method, the h i g h f r e q u e n c y n o i s e o f the t e m p e r a t u r e s i g n a l was v i r t u a l l y removed and a r e s o l u t i o n o f b e t t e r t h a n 0.005 C° o v e r s e p a r a t i o n s o f a few cm was r o u t i n e l y a c h i e v e d . Examples o f t h i s a r e found i n f i g . 21 t o 24. I I I . 3 Summary of t h e d a t a . Two c r u i s e s were made w i t h the Pumpkin m i c r o s t r u c t u r e p r o -f i l e r s i n Howe Sound. Here, the r e s u l t i n g d a t a a r e b r i e f l y p r e s e n t e d . They w i l l be d i s c u s s e d i n more d e t a i l s i n C h a p t e r s IV and V. I I I . 3 a ) The November 1973 c r u i s e : The f i r s t c r u i s e was made between November 19 and 23, 1973. Seven Pumpkin d r o p s were made. T h e i r l o c a t i o n s a r e shown i n f i g u r e 13. The r e s u l t i n g o v e r a l l p r o f i l e s a r e p r e s e n t e d i n f i g . 14 t o 20. T a b l e I I g i v e s t h e v a l u e s o f . t h e mean square t e m p e r a t u r e g r a d i e n t found i n each drop ( n o t c o r r e c t e d f o r t h e l i m i t e d r e s p o n s e o f the i n -s t r u m e n t s ) t o g e t h e r w i t h t h e l o c a t i o n and time a t w h i c h each drop was made. N o t i c e t h a t Drops P-10 and P-12 t o P-15 c o n s t i t u t e a t i m e s e r i e s o f p r o f i l e s made a t s t a t i o n Howe 4. Two d e t a i l e d p r o f i l e s from Drop P-12 and two from Drop P-13 a r e p r e s e n t e d i n f i g u r e s 21 t o 24. D u r i n g the November 1973 c r u i s e , a l a r g e number of STD c a s t s were a l s o made and t h e y r e s u l t e d i n s e v e r a l c r o s s - c h a n n e l and l o n g -c h a n n e l s e c t i o n s . One l o n g - c h a n n e l s e c t i o n i s p r e s e n t e d i n f i g . 25 and c r o s s c h a n n e l s e c t i o n s made a t Howe 4 and Howe 4.7 a r e p r e s e n t e d i n f i g . 26 and 27. I I I . 3 b) The F e b r u a r y 1974 c r u i s e : The second c r u i s e i n Howe Sound was made between F e b r u a r y 4 and 8, 1974. T h i s t i m e , b o t h b a s i n s were v i s i t e d and, f o r each d r o p , two probes were used s i m u l t a n e o u s l y . T a b l e I l i s t s a l l the drops w h i c h were made i n F e b r u a r y 1974 t o g e t h e r w i t h t h e i r t i m e and l o c a t i o n and w i t h the s e p a r a t i o n o f t h e p r o b e s a t l a u n c h and a t r e c o v e r y . F i g . 28 shows t h e l o c a t i o n o f the drops on a map o f Howe Sound. The o v e r -a l l p r o f i l e s o f t h e dro p s a r e p r e s e n t e d i n f i g . 29 t o 33. T a b l e I I I l i s t s , f o r each d r o p , the t e m p e r a t u r e change found a c r o s s t h e I n t e r -m e d i a t e Water and t h e mean square g r a d i e n t measured t h r o u g h i t ( w i t h o u t c o r r e c t i o n f o r t h e r e s p o n s e o f t h e p r o b e s ) . F i g u r e s 34 t o 37 p r e s e n t the deep p a r t o f t h e p r o f i l e s o f drops 7 t o 10 w i t h an expanded t e m p e r a t u r e s c a l e i n o r d e r t o b r i n g out the s m a l l t e m p e r a t u r e c o n t r a s t s f ound t h e r e . F i g . 38 compares STD p r o f i l e s t a k e n on J a n u a r y 22, 1974 and on F e b r u a r y 4, 1974 a t Howe 4. F i g . 39 shows a l o n g c h a n n e l STD s e c t i o n made i n the I n n e r B a s i n d u r i n g the F e b r u a r y 1974 c r u i s e and f i g . 40 shows a c r o s s - c h a n n e l s e c t i o n made a t Howe 4. C h a p t e r IV Temperature S t r u c t u r e i n Howe Sound i n November 1973 and F e b r u a r y 1974 The "Pumpkin" m i c r o s t r u c t u r e p r o f i l e r s y i e l d e d i n f o r m a t i o n about the s t r u c t u r e o f t h e d i s t r i b u t i o n o f t e m p e r a t u r e a t s c a l e s o f t e n s o f metr e s as w e l l as a t s c a l e s o f a few cm. I n t h i s c h a p t e r , t h e o v e r a l l s t r u c t u r e o f the t e m p e r a t u r e d i s t r i b u t i o n i n Howe Sound i s examined by means o f l o n g - c h a n n e l and c r o s s - c h a n n e l s e c t i o n s o f te m p e r a t u r e p r o f i l e s . Much o f the s t r u c t u r e s r e v e a l e d by t h e p r o f i l e s b e l o n g t o what G a r g e t t (1976) c a l l s t he " f i n e s t r u c t u r e " o f tempera-t u r e (see a l s o s e c t i o n 1.1). S e c o n d l y , t h e rms g r a d i e n t p r o f i l e s p r o v i d e a crude way of t a k i n g some i n f o r m a t i o n from t h e s c a l e s o f m i c r o s t r u c t u r e and p u t t i n g i t i n t o t h e l a r g e r s c a l e p i c t u r e p r o v i d e d by t h e t e m p e r a t u r e p r o f i l e s . IV.1 Temperature s t r u c t u r e i n November 1973. S i x Pumpkin o v e r a l l p r o f i l e s ( f i g . 14 t o 2 0 ) , one l o n g - c h a n n e l s e c t i o n ( f i g . 2 5 ) and two c r o s s - c h a n n e l STD s e c t i o n s ( f i g . 26 and 27) a r e used h e r e t o show the d i s t r i b u t i o n o f t e m p e r a t u r e and rms tempera-t u r e g r a d i e n t i n the I n n e r B a s i n o f Howe Sound i n November 1973. B o t t l e c a s t d a t a c o l l e c t e d on November 13, 1973 ( f i g . 9) showed t h a t the w a t e r p r e s e n t b e f o r e t h e r e n e w a l , c a l l e d O l d Water, had t e m p e r a t u r e s l o w e r t h a n 8.4 °C w h i l e the r e c e n t l y a r r i v e d w a t e r , c a l l e d New Water, had t e m p e r a t u r e s o f 8.6 °C o r more. A t s t a t i o n Howe 3.8, j u s t i n s i d e t he s i l l , t h e Pumpkin drop P - l l was made on November 21, 1973 ( p r o f i l e i n f i g . 1 5 , l o c a t i o n i n f i g . 1 3 ) . Below 20 m, t e m p e r a t u r e s between 8.6 and 8.8 °C a r e found o v e r t h e whole p r o f i l e , i n d i c a t i n g t h a t New Water i s p r e s e n t t h e r e . Between 20 and 80 m, t h e r e a r e many l a y e r s o f v a r y i n g t e m p e r a t u r e w i t h t h i c k n e s s e s o f 1 t o 10 m. A t s t a t i o n Howe 4, a c r o s s - c h a n n e l STD s e c t i o n was made ( f i g . 2 6 ) . The p r o f i l e made on t h e s o u t h - e a s t e r n s i d e o f t h e c h a n n e l shows t e m p e r a t u r e s o f 8.6 t o 8.8 °C everywhere b e l o w 30 m, i n d i c a t i n g t h a t t h i s s i d e o f t h e i n l e t i s o c c u p i e d by New Water. The p r o f i l e made on the n o r t h - w e s t e r n s i d e o f t h e c h a n n e l shows w a t e r o f 8.3 t o 8.5 °C.between 75 and 175 m, i n d i c a t i n g t h a t O l d Water o c c u p i e s t h a t p a r t o f t h e wa t e r column. The r e s t o f t h e w a t e r column i s o c c u p i e d by New Water. The p r o f i l e made i n t h e c e n t e r o f t h e c h a n n e l a l s o shows O l d Water i n the same d e p t h range w i t h a 20 m t h i c k l a y e r o f New Water n e a r 100 m d e p t h . Drops P-10 and P-12 t o P-15 were a l s o made a t Howe 4, n e a r t h e c e n t r e o f the c h a n n e l ( f i g . 1 4 and f i g . 1 6 t o 2 0 ) . Drops P-12 t o P-15 were made a t h o u r l y i n t e r v a l s ( T a b l e I I ) . On t h e s e p r o f i l e s , i n t he depth range o f 30 t o 100 m, t h e r e a r e many t e m p e r a t u r e v a r i a -t i o n s a t s c a l e s o f 1 t o 30 m. Even the t h i c k e r " l a y e r s " o f t e n cannot be t r a c e d on two s u c c e s s i v e p r o f i l e s . I n some c a s e s , the t e m p e r a t u r e o f the " l a y e r s " a s s o c i a t e s them w i t h O l d Water o r New Water. A t s t a t i o n Howe 4.3, a n o t h e r STD c r o s s - c h a n n e l s e c t i o n was made ( n o t shown h e r e ) . I n i t , New Water was found o n l y b e l o w 200 m and above 100 m; i n between t h e r e was O l d Water. I n the STD p r o f i l e made n e a r t h e S-E s i d e o f t h e c h a n n e l , the O l d Water was found between 75 and 150 m o n l y . A t s t a t i o n Howe 4.7, one STD p r o f i l e was made on each s i d e o f t h e c h a n n e l ( f i g . 2 7 ) and Drop P-16 was made n e a r t h e S-E s i d e o f t h e c h a n n e l ( f i g . 2 0 ) . I n a l l t h e s e p r o f i l e s , New Water was a g a i n found o n l y below 200 m and above 50 m. Between 50 and 75 m, the w a t e r on the STD p r o f i l e s c o u l d n o t be r e a d i l y c l a s s i f i e d as "new" o r " o l d " . Between 30 and 75 m, the t e m p e r a t u r e p r o f i l e o f drop P-16 l o o k e d v e r y s i m i l a r t o the p r o f i l e s o b t a i n e d a t s t a t i o n Howe 4 (see f o r i n s t a n c e P-13 i n f i g . 1 9 ) . I n Drops P-10 t o P-16, two a s p e c t s o f t h e rms g r a d i e n t p r o -f i l e s s t r i k e a t f i r s t g l a n c e . F i r s t l y t h e rms g r a d i e n t o c c u r s i n " b u r s t s " o r " p a t c h e s " w h i c h appear t o be a t most a few metr e s t h i c k . S e c o n d l y , t h e r e a r e " q u i e t " r e g i o n s where, f o r up t o 50 m, v e r y l i t t l e rms g r a d i e n t i s found. The r e g i o n s w i t h l i t t l e rms g r a d i e n t o c c u r i n r e g i o n s where the t e m p e r a t u r e i s u n i f o r m w i t h d e p t h . E x a m i n a t i o n o f any o f t h e p r o f i l e s a l s o r e v e a l s t h a t some sha r p t e m p e r a t u r e changes a r e accompanied by no l a r g e rms g r a d i e n t v a l u e s and a l s o t h a t some mi n o r t e m p e r a t u r e changes (where the l o c a l mean g r a d i e n t i s perhaps weaker) show v e r y h i g h rms g r a d i e n t i n t e n s i t i e s . T a b l e I I p r e s e n t s the mean square g r a d i e n t v a l u e s found i n each drop below about 20 m. The average v a l u e f o r a l l drops i s ~*3 o 2 25 x 10 ( C/m) . The v a l u e s found i n i n d i v i d u a l d r o p s v a r y f r o m t h i s v a l u e by up t o a f a c t o r o f two. Most o f the v a r i a n c e o f t h e g r a d i e n t comes from t h e upper 100 m, i n the r e g i o n where t h e r e a r e a l s o many te m p e r a t u r e v a r i a t i o n s . Near 200 m, some drops show a t e m p e r a t u r e r i s e and p a t c h e s o f rms g r a d i e n t . U n f o r t u n a t e l y , none o f t h e probes went s i g n i f i c a n t l y deeper t h a n t h i s . On t h e STD p r o f i l e s , t h e r e i s a t r a n -s i t i o n from O l d Water t o New Water near 200 m. IV.2 Temperature s t r u c t u r e i n F e b r u a r y 1974. D u r i n g t h e second m i c r o s t r u c t u r e c r u i s e i n Howe Sound, be-tween F e b r u a r y 4 and 8, 1974, b o t h b a s i n s were v i s i t e d and each drop was made w i t h two pr o b e s i n an e f f o r t t o g a i n some i n f o r m a t i o n on t h e l a t e r a l e x t e n t o f the m i c r o s t r u c t u r e p a t c h e s . N i n e d o u b l e d r o p s were made; t h e i r p o s i t i o n , t i m e and s e p a r a t i o n o f t h e p r o b e s a t l a u n c h and r e c o v e r y a r e l i s t e d i n T a b l e I . O n l y f i v e d o u b l e p r o f i l e s a r e p r e s e n t e d h e r e . These a r e Drop 6 t o Drop 10. One STD l o n g - c h a n n e l s e c t i o n and one c r o s s - c h a n n e l STD s e c t i o n a t Howe 4 were t a k e n . a) Recent e v o l u t i o n o f w a t e r p r o p e r t i e s i n Howe Sound: F i g u r e 38 compares STD p r o f i l e s made J a n u a r y 22, 1974 and F e b r u a r y 4, 1974 (two weeks a p a r t ) i n the O u t e r B a s i n and i n the I n n e r B a s i n a t Howe 4.5. F i g . 38 shows t h a t a s i g n i f i c a n t t e m p e r a t u r e d e c r e a s e has t a k e n p l a c e above 100 m i n t h e two weeks w h i c h p r e c e d e d t h e F e b r u a r y m i c r o s t r u c t u r e c r u i s e . I n t h e I n n e r B a s i n , a s i m i l a r t e m p e r a t u r e d e c r e a s e has o c c u r r e d i n the upper 60 t o 70 m. I n t h e Deep Water, the STD p r o f i l e s r e v e a l no s i g n i f i c a n t changes i n temper-a t u r e . The d i s c u s s i o n p r e s e n t e d i n c h a p t e r I I about t h e I n t e r m e d i a t e Water i n d i c a t e s t h a t such a t e m p e r a t u r e change o c c u r r e d because t h e f o r m e r I n t e r m e d i a t e Water has been r e p l a c e d by some new, c o l d e r w a t e r I t i s i n t e r e s t i n g a t t h i s p o i n t t o m e n t i o n t h a t an oceano-g r a p h i c c r u i s e a l s o v i s i t e d Howe Sound on March 15, 1974 (I.O.U.B.C, 1974). I t r e v e a l e d t h a t no major change i n t h e o v e r a l l t e m p e r a t u r e s t r u c t u r e o f t h e w a t e r column had o c c u r r e d s i n c e t h e F e b r u a r y 1974 c r u s e . I n t h e Deep Water below 150 m, the l o w e s t t e m p e r a t u r e d i f f e r e f r o m the h i g h e s t one by 0.17 C°. T h i s compares t o 0.3 C° i n J a n u a r y 1974 and 0.5 C° i n November 1973. b) Temperature s t r u c t u r e i n t h e Ou t e r B a s i n : On F e b r u a r y 5, 1974, f o u r d o u b l e Pumpkin drops and f o u r STD c a s t s were made i n R a m i l l i e s C h a n n e l (Outer B a s i n , f i g . l ) . O n ly t h e o v e r a l l p r o f i l e o f Drop 6 has been p r o c e s s e d ( f i g . 29, l o c a t i o n shown i n f i g . 2 8 ) . The STD and Pumpkin p r o f i l e s were made s e v e r a l h o u r s a p a r t and d i f f e r o n l y a t s c a l e s o f 5 t o 10 m, n e a r t h e l i m i t o f t h e s p a t i a l r e s o l u t i o n o f the STD. I n o r d e r t o make com p a r i s o n s e a s i e r , t he rms g r a d i e n t p r o -f i l e s o f Drop 6 have been put back t o back. The t e m p e r a t u r e p r o f i l e s have been o f f s e t from each o t h e r by 1.0 C°. The l e f t rms g r a d i e n t p r o f i l e accompanies t h e l e f t t e m p e r a t u r e p r o f i l e . The Pumpkins were l a u n c h e d w i t h a s e p a r a t i o n o f 20 m. T a b l e I ( d i s c u s s e d i n C h a p t e r I I I ) i n d i c a t e s t h a t , d u r i n g the d e s c e n t , the s e p a r a t i o n o f t h e p r o b e s p r o -b a b l y s t a y e d between 10 and 40 m. Drop 6 ( f i g . 2 9 ) shows many a b r u p t t e m p e r a t u r e changes and l o c a l t e m p e r a t u r e i n v e r s i o n s w i t h r e s p e c t t o t h e main t r e n d . These were n o t v i s i b l e on the t e m p e r a t u r e p r o f i l e s o b t a i n e d w i t h the STD probe. C a r e f u l e x a m i n a t i o n o f the two t e m p e r a t u r e p r o f i l e s o f Drop 6 shows t h a t d i f f e r e n c e s between t h e two o c c u r e s s e n t i a l l y a t s c a l e s s m a l l e r t h a n 2 m ( t h e p r o f i l e s a r e made from 0.4 m a v e r a g e s ) . The p r o f i l e s o f the rms g r a d i e n t show t h a t most o f the v a r i -ance a r i s e s from a few p a t c h e s w i t h a t h i c k n e s s o f one t o t h r e e m e t r e s and w i t h i n t e n s i t i e s o f \ t o \\ C°/m (rms, u n c o r r e c t e d f o r t h e f r e -quency r e s p o n s e o f the p r o b e s ) . A l a r g e p a t c h found i n one p r o f i l e may c o r r e s p o n d t o no p a t c h a t a l l i n the o t h e r p r o f i l e ( s e e f o r i n s t a n c e n e a r 105 m). As i n the November 1973 d r o p s , r e g i o n s o f the p r o f i l e s where t h e t e m p e r a t u r e i s u n i f o r m show l i t t l e rms g r a d i e n t and, i n t he r e s t o f t h e p r o f i l e s , t h e r e i s no c l e a r r e l a t i o n s h i p between the v a l u e o f t h e rms g r a d i e n t and t h a t o f t h e l o c a l mean g r a d i e n t . The mean square g r a d i e n t a v e r a g e d o v e r the whole p r o f i l e ( n o t i n c l u d i n g t he upper 20 m) and the n e t t e m p e r a t u r e d i f f e r e n c e f o und a c r o s s i t a r e g i v e n i n T a b l e I I I . The mean sq u a r e g r a d i e n t a v e r -aged o v e r b o t h p r o f i l e s i s 26.5 x 10 ^ (C°/m)^. The mean square g r a d i e n t v a l u e o f p r o f i l e A i s about t w i c e as l a r g e as t h a t o f p r o f i l e B. F i g u r e 29 shows c l e a r l y t h a t t h i s i s due t o t h e o c c u r r e n c e o f d i f f e r e n t rms g r a d i e n t p a t c h e s i n each p r o f i l e . I n each p r o f i l e , t h r e e o r f o u r p a t c h e s can a c c o u n t f o r more th a n 90% of the g r a d i e n t v a r i a n c e . c) Temperature s t r u c t u r e i n t h e I n n e r B a s i n ' s I n t e r m e d i a t e Water: On F e b r u a r y 6, 1974, f o u r d o u b l e Pumpkin d r o p s and a number of STD p r o f i l e s were made i n the I n n e r B a s i n o f Howe Sound. Here, o n l y t h e p a r t o f t h e p r o f i l e s w h i c h comes f r o m t h e I n t e r m e d i a t e Water (10 t o 100 m, see c h a p t e r I I ) i s examined. The Deep Water i s r e s e r v e d f o r s e c t i o n d ) . Drops 7 t o 10 a r e shown i n f i g . 30 t o 33 and t h e i r l o c a -t i o n i n Howe Sound i s shown i n f i g . 2 8 . One l o n g - c h a n n e l STD s e c t i o n and one c r o s s - c h a n n e l STD s e c t i o n a r e p r e s e n t e d i n f i g . 3 9 and 40. A l l t he t e m p e r a t u r e p r o f i l e s (STD and Pumpkins) d i f f e r f rom each o t h e r m o s t l y i n the 30 t o 70 m range. They can be grouped a c c o r d -i n g t o t h e i r r e s e m b l a n c e . -Drop 7 ( f i g . 3 0 ) and STD #7 ( f i g . 4 0 ) show a l a y e r o f r e l a -t i v e l y u n i f o r m t e m p e r a t u r e bounded by two sharp t e m p e r a t u r e s t e p s . I n f i g . 3 0 , t h i s l a y e r has been l a b e l l e d " l a y e r B". STD $7 was o b t a i n e d n e a r t h e S-E s i d e o f t h e c h a n n e l a t Howe 4 w h i l e Drop 7 was a l s o o b t a i n e d a t Howe 4. -Drops 8 and 9 ( f i g . 3 1 and 32) and STD #6 and #8 ( f i g . 3 9 and 40) have a p r o f i l e where t h e " l a y e r B" does n o t show c l e a r l y . O t h e r -w i s e t h e y a r e v e r y s i m i l a r t o the p r o f i l e s o f Drop 7 and STD #7. They were o b t a i n e d a t Howe 4, ne a r the c e n t e r o f t h e c h a n n e l . -Drop 10 ( f i g . 3 3 ) and STD #5, #9, and #10 ( f i g . 3 9 and 40) have i n common a t e m p e r a t u r e " b u l g e " l a b e l l e d on Drop 10 as " l a y e r D". The higher r e s o l u t i o n of the Pumpkins shows that the "bulge" consists of a temperature maximum followed about 10 m deeper by a minimum (Drop 1 0 ) ; these seem to be made of a number of steps a few metres thick. That type of structure was found at Howe 4.7, Howe 4.5 and Howe 4 on the N-W side of the channel. The rms gradient p r o f i l e s of Drops 7 to 10 (Inner Basin Intermediate Water) share many features with those of Drop 6 (Outer Basin). Most of the gradient variance i s concentrated i n several patches. Maximum rms gradient values are 5 to 1 C°/m. Regions of uniform temperature show l i t t l e rms gradient. However, there are also several s t r i k i n g differences between the rms gradient p r o f i l e s of the Inner Basin and the Outer Basin. -The rms gradient patches are thinner and fewer i n Drops 7 to 9 than i n Drop 6. -The major rms gradient patches are c l o s e l y associated with the major temperature steps (mostly i n Drops 7 and 8 ) . -Rms gradient patches found i n one p r o f i l e of a p a i r do usually correspond to patches i n the other p r o f i l e of the p a i r as well. This i s true even for minor patches i n Drops 7 to 9. -The temperature p r o f i l e s of Drops 7 to 9 contain smaller and perhaps fewer temperature inversions (with respect to the main trend) than Drop 6. Table III presents the temperature diff e r e n c e and the mean square gradient calculated i n the Intermediate Water of each drop. The average c a l c u l a t e d from Drops 7 t o 10 i s 8.6 x 10 (C°/m) . The h i g h e s t v a l u e and t h e second l o w e s t one a r e found i n the same d o u b l e drop (Drop 8 ) . The v a l u e s found i n the I n n e r B a s i n a r e thus 2 t o 4 t i m e s s m a l l e r t h a n t h o s e f o u n d i n the Ou t e r B a s i n (no c o r r e c t i o n made i n the f r e q u e n c y r e s p o n s e ) . I n Drops 7, 8 and 9, the h i g h rms g r a d i e n t v a l u e s seem t o be c l o s e l y r e l a t e d t o t h e t e m p e r a t u r e s t e p s ( f i n e s t r u c t u r e ) . The rms g r a d i e n t p a t c h e s appear t o e x t e n d l a t e r a l l y o v e r d i s t a n c e s l a r g e r t h a n about 20 m s i n c e t h e y a r e u s u a l l y f ound on b o t h p r o f i l e s , j u s t l i k e t he t e m p e r a t u r e s t e p s t h e m s e l v e s . I n Drop 10, f u r t h e r up i n l e t , t he p i c t u r e i s more c o n f u s e d because t h e t e m p e r a t u r e p r o f i l e s r e v e a l numer-ous f i n e s t r u c t u r e l a y e r s accompanied by g r a d i e n t v a r i a n c e . Only one s u c c e s s f u l Pumpkin drop was o b t a i n e d i n t h i s t y p e o f f i n e s t r u c t u r e b u t the STD s e c t i o n s i n d i c a t e t h a t such f i n e s t r u c t u r e might have been found o v e r most of t h e i n l e t . d) Temperature s t r u c t u r e i n t h e I n n e r B a s i n ' s Deep Water: I n t h i s s e c t i o n , t h e Deep Water p a r t o f t h e Pumpkin p r o f i l e s i s examined. The Deep Water, as d e f i n e d w i t h r e s p e c t t o t h e I n t e r m e d -i a t e Water i n c h a p t e r I I , i s found i n t h e I n n e r B a s i n below 100 m. A t t h a t d e p t h , the STD p r o f i l e s show no f i n e s t r u c t u r e . The t e m p e r a t u r e s c a l e o f t h e Pumpkin has been expanded so t h a t s m a l l t e m p e r a t u r e d i f f e r e n c e s become e a s i l y d e t e c t a b l e . F i g . 3 4 t o 37 show t h e Deep Water p a r t o f Drops 7 t o 10 w i t h an expanded s c a l e o f t e m p e r a t u r e . The rms g r a d i e n t s c a l e i s the same as p r e v i o u s l y t o make com p a r i s o n s e a s i e r . I n a l l t h e Pumpkin p r o f i l e s , a s l i g h t t e m p e r a t u r e maximum i s f ound n e a r 90 t o 95 m and a s l i g h t minimum i s found n e a r 105 t o 110 m. Drops 8 and 9 s t o p n e a r 125 m. Drop 10 shows a t e m p e r a t u r e minimum n e a r 125 m and a f t e r t h i s , i t s t e m p e r a t u r e i n c r e a s e s mono-t o n i c a l l y w i t h depth u n t i l t h e end o f t h e d r o p , n e a r 170 m. I n Drop 7, t h e Deep Water t e m p e r a t u r e p r o f i l e i s v e r y s i m i l a r t o t h a t o f Drop 10, e x c e p t between 120 and 165 m. T h e r e , Drop 7 shows two l a y e r s o f w a t e r w i t h t e m p e r a t u r e s 0.035 C° warmer t h a n t h o s e o f t h e w a t e r found above o r below them a t s i m i l a r d e p t h i n Drop 10. Such l a y e r e d f i n e s t r u c t u r e where the w a t e r p r o p e r t i e s a l t e r n a t e between two t y p e s i s o f t e n d e s c r i b e d as " i n t e r l e a v i n g " , an e x p r e s s i o n w h i c h s u g g e s t s t h a t t h e r e a r e two d i s t i n c t b o d i e s o f w a t e r and t h a t t h e i n s t r u m e n t s went t h r o u g h t h e i r i r r e g u l a r boundary. The d e n s i t y d i f f e r e n c e between the two w a t e r t y p e s i s n e g l i g i b l e ; t he s a l i n i t y d i f f e r e n c e i s c l o s e t o 0.006 °/oo. I n t h e Deep Water p a r t o f Drop 7 ( f i g . 3 4 ) , s i g n i f i c a n t rms g r a d i e n t v a l u e s a r e found o n l y i n a s s o c i a t i o n w i t h t h e l a y e r e d s t r u c -t u r e . The t h i c k n e s s e s o f the p a t c h e s found by the two p r o b e s d i f f e r by about 4 m. W i t h i n t h e p a t c h e s , t h e rms g r a d i e n t i s d i f f e r e n t l y d i s t r i b u t e d i n each p r o f i l e o f t h e p a i r . D i f f e r e n c e s a r e a l s o f o u n d i n t h e p r o f i l e s o f t e m p e r a t u r e a t s c a l e s o f up t o s e v e r a l m e t r e s . I n Drop 8 ( f i g . 3 5 ) , a p a t c h o f rms g r a d i e n t 5 t o 10 m t h i c k was d e t e c t e d n e a r 100 m. On each p r o f i l e o f t h e p a i r , t he rms g r a d i e n t was d i f f e r e n t l y d i s t r i b u t e d . The p a t c h was accompanied by no remark-a b l e f i n e s t r u c t u r e f e a t u r e o f t h e t e m p e r a t u r e p r o f i l e . A t s i m i l a r d e p t h , none o f the o t h e r Pumpkin p r o f i l e s showed any s i g n i f i c a n t g r a d i e n t v a r i a n c e . Drops 9 and 10 ( f i g . 3 6 and 37) showed no r e m a r k a b l e rms g r a d i e n t p a t c h e s i n t h e Deep Water. IV.3 D i s c u s s i o n . a) An I n t e r m e d i a t e Water c i r c u l a t i o n p a t t e r n ? I n November 1973, t h e c r o s s - c h a n n e l and l o n g - c h a n n e l STD and b o t t l e c a s t s e c t i o n s showed t h a t between t h e s i l l and s t a t i o n Howe 4.5, c r o s s - c h a n n e l t e m p e r a t u r e d i f f e r e n c e s were s i m i l a r t o l o n g -c h a n n e l ones. New Water was found m o s t l y on t h e S-E s i d e o f t h e c h a n n e l and n e a r t h e s i l l . I n F e b r u a r y 1974, i n t h e range o f 30 t o 70 m, d i f f e r e n c e s i n t h e a s p e c t o f t h e t e m p e r a t u r e p r o f i l e s e n c o u n t -e r e d i n a c r o s s - c h a n n e l s e c t i o n a t Howe 4 were s i m i l a r t o t h o s e e n c o u n t e r e d i n a l o n g - c h a n n e l s e c t i o n a l o n g t h e c e n t e r o f t h e i n l e t . D a h l (1977) has o b s e r v e d a n a l o g o u s c o n t r a s t s i n O s l o f j o r d . He i n t e r p r e t e d them as an i n d i c a t i o n t h a t c u r r e n t s w i t h i n t h a t f j o r d a r e s u b j e c t t o C o r i o l i s f o r c e and t h a t t h e y appeared t o be i n g e o s t r o -p h i c e q u i l i b r i u m w i t h t he d e n s i t y f i e l d . B u c k l e y (1977) a l s o m e n t i o n e d t h a t C o r i o l i s f o r c e would e x p l a i n why t h e New Water o f November 1973 was f o u n d m o s t l y on the S-E s i d e o f t h e c h a n n e l s i n c e t h i s i s t h e " r i g h t hand s i d e " f o r w a t e r e n t e r i n g t h e I n n e r B a s i n f r o m t h e Ou t e r B a s i n . I n F e b r u a r y 1974, t h e c r o s s - c h a n n e l d i f f e r e n c e s f ound a t Howe 4 may be i n t e r p r e t e d i n t h e same f a s h i o n ( f i g . 4 0 ) . These i n t e r p r e t a t i o n s s u g g e s t t h a t a mean c o u n t e r - c l o c k w i s e c i r c u l a t i o n p a t t e r n e x i s t i n t h e I n t e r m e d i a t e Water o f t h e I n n e r B a s i n between t h e s i l l and Howe 4.5, and t h a t t h i s p a t t e r n may a c c o u n t f o r changes i n o c e a n o g r a p h i c p r o p e r t i e s w h i c h were shown t o o c c u r on time s c a l e s s h o r t e r t h a n one month ( c h a p t e r I I ) . b) The Osborn-Cox model: - O u t l i n e o f t h e Osborn-Cox model: The f i r s t e f f o r t f o r p u t t i n g t e m p e r a t u r e m i c r o s t r u c t u r e i n -f o r m a t i o n t o use i n an o c e a n o g r a p h i c model i s due t o Osborn and Cox (19 7 2 ) . I n t h i s s e c t i o n , a v e r y b r i e f a c c o u n t o f t h i s model w i l l be g i v e n . I t a p p l i e s t o r e g i o n s o f a w a t e r column where a s t e a d y mean g r a d i e n t i s fo u n d ; i n t h e Howe Sound d a t a , i t m i g h t a p p l y t o r e g i o n s o f t h e F e b r u a r y 1974 I n t e r m e d i a t e Water. The complete d e r i v a t i o n o f t h e model i s g i v e n i n Osborn and Cox (197 2 ) . The e s s e n c e o f t h e model can be d e r i v e d s t a r t i n g from t h e F o u r i e r h e a t d i f f u s i o n e q u a t i o n f o r an i n c o m p r e s s i b l e f l u i d : ^ e = ^ v 2 e ( i v . i ) where D/Dt d e n o t e s t h e " m a t e r i a l d e r i v a t i v e " o p e r a t o r and r e -p r e s e n t s t h e c o e f f i c i e n t o f m o l e c u l a r h e a t d i f f u s i v i t y . I t i s assumed t h a t r a d i a t i v e t r a n s f e r s a r e n e g l i g i b l e . N e x t , one uses t h e R e y n o l d s e x p a n s i o n o f v a r i a b l e s : u. — u. + u! u. = <u.> 1 1 1 1 1 (IV.2) E < 6 > where < > denotes t h e a v e r a g i n g made o v e r some " s u i t a b l e " time and space s c a l e . One expands e q u a t i o n (IV.1) w i t h the R e y n o l d s v a r i a b l e s , m u l t i p l i e s i t by Q' and t h e n p e r f o r m s the a v e r a g i n g . The d i v e r g e n c e of t he mean f i e l d i s assumed t o be n e g l i g i b l e and the t e m p e r a t u r e f l u c t u a t i o n s a r e t a k e n t o be homogeneously d i s t r i b u t e d . E q u a t i o n (IV.1) t h e n becomes: 9_ < e^ _2 > = _ < u f .e*> • 39 - K < ( V 0 * ) 2 > n ~. 3t 2 . 1 3 X . U ; (1) (2) (3) I n e q u a t i o n ( I V . 3 ) , term (3) i s alw a y s n e g a t i v e and i n d i c a t e s t h a t m o l e c u l a r d i f f u s i o n a l w a y s a c t s as a " s i n k " f o r t e m p e r a t u r e v a r i -ance. Term (2) r e p r e s e n t s t h e i n t e r a c t i o n s between the v e l o c i t y f l u c -t u a t i o n s and t h e t e m p e r a t u r e f i e l d and a c t s g e n e r a l l y as a " s o u r c e " o f t e m p e r a t u r e v a r i a n c e . The p r o d u c t <u^9'> c o r r e s p o n d s t o a R e y n o l d s f l u x o f h e a t . F o r t h e Osborn-Cox model, one assumes a s t e a d y s t a t e and drop s term ( 1 ) . One t h e n assumes t h a t l a t e r a l g r a d i e n t s o f t h e mean f i e l d o r l a t e r a l eddy f l u x e s a r e n e g l i g i b l e , b u t t h a t v e r t i c a l ones a r e s i g n i f i c a n t . E q u a t i o n (IV.3) t h e n r e d u c e s t o : < w'0' > 30^ = - X < ( v e ' ) 2 > (IV.4) o r , a f t e r i s o l a t i n g t h e v e r t i c a l eddy f l u x : < w'0' > = ( V 0 ' ) 2 8 6 ( I V ' 5 ) 8 Z E q u a t i o n (IV.5) p r o v i d e s an a t t r a c t i v e method f o r e s t i m a t i n g v e r t i c a l h e a t t r a n s f e r s u s i n g t e m p e r a t u r e m i c r o s t r u c t u r e o b s e r v a t i o n s p r o v i d e d t h a t t h e r e g i o n o f t h e w a t e r column where i t i s a p p l i e d r e s -p e c t s t h e a s s u m p t i o n s o f t h e model. E q u a t i o n (IV.5) can a l s o be g i v e n a shape s i m i l a r t o t h a t o f t h e h e a t d i f f u s i o n p r o blem: < w» e» > — K« || d v . 6 ) w i t h : < ( V 0 * ) 2 > and: U ~ (IV.8) (3Z) I n e q u a t i o n (IV.7) ^ i s an "eddy c o e f f i c i e n t " o f v e r t i c a l h e a t d i f -f u s i o n and P» i s c a l l e d t h e Cox Number, a n o n - d i m e n s i o n a l r a t i o w h i c h has become w i d e l y a c c e p t e d f o r d e s c r i b i n g the " i n t e n s i t y " o f tempera-t u r e m i c r o s t r u c t u r e w i t h i n a m o n o t o n i c t e m p e r a t u r e p r o f i l e . -Cox numbers i n t h e F e b r u a r y 1974 d a t a : I n t h e F e b r u a r y 1974 d a t a , t h e r e a r e two r e g i o n s of t h e w a t e r column where t e m p e r a t u r e i n c r e a s e s m o n o t o n i c a l l y w i t h d e p t h . The f i r s t one i s f o u n d between 20 and 35 m i n Drops 7 t o 10 ( f i g . 2 9 t o 33) and i t i s l a b e l l e d on Drop 7 and Drop 10 as " l a y e r A". The second r e g i o n i s a l s o found i n Drop 7 t o Drop 10 between 65 and 95 m and has been l a b e l l e d " l a y e r C". I n l a y e r A, c a l c u l a t i o n s d e r i v e d d i r e c t l y f rom the d a t a show t h a t the mean v e r t i c a l t e m p e r a t u r e g r a d i e n t i s , about 0.0135 C°/m and -3 the mean square v e r t i c a l t e m p e r a t u r e g r a d i e n t i s a t l e a s t 9 x 10 (C°/m) 2. T h i s v a l u e does n o t t a k e i n t o a c c o u n t t h e l i m i t e d s p a t i a l r e s o l u t i o n o f t h e p r o b e s and t h e Cox Number p r e s e n t e d h e r e does n o t i n c l u d e any i n f o r m a t i o n about t h e h o r i z o n t a l component o f t h e temper-a t u r e g r a d i e n t a t m i c r o s t r u c t u r e s c a l e s . I t y i e l d s : < (__£')•2 > G> > ( 8 Z ) * 50 (36) 2 OZ) I n l a y e r C, d e t a i l e d p r o f i l e s p r e s e n t e d i n c h a p t e r V w i l l show t h a t most of t h e v e r t i c a l g r a d i e n t v a r i a n c e o c c u r s a t s c a l e s w h i c h can be r e s o l v e d by the Pumpkins. Depending on how one chooses t h e a v e r a g i n g 39 i n t e r v a l and w h i c h p r o f i l e one u s e s , one o b t a i n s Cox Number e s t i m a t e s o f : 4 t o 25 The q u e s t i o n a r i s e s - can t h e s e v a l u e s be i n t e r p r e t e d as an eddy c o e f f i c i e n t o f v e r t i c a l d i f f u s i o n i n Howe Sound's I n t e r m e d i a t e Water? A number of c o n s i d e r a t i o n s have t o be t a k e n i n t o a c c o u n t . - I t i s n o t c l e a r t h a t t h e h o r i z o n t a l terms o f h e a t t r a n s p o r t can be n e g l e c t e d w i t h i n Howe Sound. S e c t i o n IV.3.a s u g g e s t s t h e o p p o s i t e . - I t i s p o s s i b l e t h a t most o f t h e v e r t i c a l t r a n s p o r t o f h e a t i s a s s o c i a t e d w i t h p r o c e s s e s g o i n g on n e a r t h e w a l l s o f t h e i n l e t o r i n c o n j u n c t i o n w i t h s t r o n g w eather e v e n t s . I n t h e s e c a s e s , t h e Osborn-Cox model s t i l l a p p l i e s on t h e c o n d i t i o n t h a t t h e t e m p e r a t u r e g r a d i e n t v a r i a n c e a s s o c i a t e d w i t h t h e s e p r o c e s s e s i s t a k e n i n t o a c c o u n t . Here, i t was n o t . -The l i m i t e d s p a t i a l r e s o l u t i o n of t h e pr o b e s r e s u l t s i n e s t i m a t e s o f t h e v e r t i c a l g r a d i e n t v a r i a n c e w h i c h a r e too low by an unknown f a c t o r . The h o r i z o n t a l component o f t h e g r a d i e n t v a r i a n c e a r e n o t o b s e r v e d . L a y e r C ( f i g . 30 and 33) p r e s e n t s an i n t e r e s t i n g p r o b l e m i n t h a t i t i s l o c a t e d m o s t l y below maximum s i l l d e p t h and i t s p r o f i l e has a shape r e m i n i s c e n t o f p r o f i l e s f o u n d i n h e a t d i f f u s i o n p r o b l e m s . One would l i k e t o v e r i f y i f an eddy d i f f u s i v i t y c o e f f i c i e n t d e r i v e d w i t h the Cox Number c o u l d be c o m p a t i b l e w i t h the f o r m a t i o n o f l a y e r C by v e r t i c a l t u r b u l e n t t r a n s p o r t o r i f h o r i z o n t a l exchanges p r o v i d e a more l i k e l y mechanism. On J a n u a r y 24, 1974, STD p r o f i l e s showed t h a t t h e w a t e r column between 50 and 100 m was n e a r l y i s o t h e r m a l ( f i g . 3 8 ) . L e t us t h e n assume t h a t between 60 and 90 m, t h e t e m p e r a t u r e was i n i t i a l l y u n i f o r m and e q u a l t o t h e t e m p e r a t u r e o f t h e w a t e r f o u n d below 90 m, and t h a t i t has been r e d u c e d by v e r t i c a l eddy d i f f u s i o n . T h i s p r o b -lem i s s i m i l a r t o t h a t o f a s e m i - i n f i n i t e medium i n c o n t a c t w i t h a c o n s t a n t t e m p e r a t u r e s o u r c e . I n t h i s p r o b l e m , 70% o f t h e t e m p e r a t u r e change o c c u r s w i t h i n a d i s t a n c e H f r o m t h e s o u r c e such t h a t : H 2 = 2 ^ t (IV.9) where ^ e i s t h e eddy c o e f f i c i e n t o f v e r t i c a l h e a t d i f f u s i o n and t i s t h e t i m e e l a p s e d s i n c e t h e c o n s t a n t t e m p e r a t u r e s o u r c e was a p p l i e d t o t h e s e m i - i n f i n i t e medium. U s i n g e q u a t i o n s (IV.8) and ( I V . 7 ) , one o b t a i n s a Cox Number o f : § = H 2 (IV.10) I n l a y e r C, the v a l u e o f H on F e b r u a r y 6, 1974 i s about 30 m (see Drops 7 t o 10, f i g . 34 t o 3 7 ) . The maximum ti m e e l a p s e d s i n c e the " c o n s t a n t t e m p e r a t u r e s o u r c e " c o n d i t i o n was a p p l i e d i s about 1.2 x 10^ sec (two weeks). U s i n g a m o l e c u l a r h e a t d i f f u s i o n -7 2 c o e f f i c i e n t o f 1.4 x 10 m / s e c we f i n d t h a t t h e v a l u e o f t h e Cox Number s h o u l d be about 2600. T h i s v a l u e i s a t l e a s t a f a c t o r o f 100 l a r g e r t h a n t h e v a l u e s r e p o r t e d e a r l i e r on t h e b a s i s of the Pumpkin d a t a . One c o n c l u d e s t h a t l a y e r C was formed p e r h a p s t h r o u g h i n t e r -m i t t e n t " c a t a s t r o p h i c " m i x i n g e v e n t s w h i c h were n o t o b s e r v e d o r , more l i k e l y , t h a t t h e shape o f t h e p r o f i l e o f l a y e r C r e s u l t s f r o m t h e a d v e c t i o n of w a t e r coming f r o m the O u t e r B a s i n and t h a t t h e shape o f the p r o f i l e does n o t r e s u l t from v e r t i c a l m i x i n g . c) A model f o r an i s o l a t e d and inhomogeneous volume of f l u i d : The Osborn-Cox model i s a p a r t i c u l a r case d e r i v e d f r o m e q u a t i o n ( I V . 3 ) . Here, a n o t h e r p a r t i c u l a r c a s e i s p r e s e n t e d because i t may be b e t t e r s u i t e d f o r a d e s c r i p t i o n o f t h e Deep Water o f Howe Sound's I n n e r B a s i n . Take a volume o f f l u i d ( w a t e r ) w h i c h has an inhomogeneous t e m p e r a t u r e d i s t r i b u t i o n and w h i c h undergoes no h e a t exchanges w i t h i t s s u r r o u n d i n g s . Then, i f a v e r a g i n g i s done o v e r t h e whole volume, t h e t r a n s p o r t ' terms o f e q u a t i o n (IV.3) can be dropped and i t becomes: _ < B — - • -K < ( v e ' ) 2 > «v.ii) 3t 2 I n t h i s c a s e , 0 ( w h i c h does n o t appear e x p l i c i t l y i n t h e e q u a t i o n ) i s t h e mean t e m p e r a t u r e w i t h i n t h e volume and i t i s e x p e c t e d t o s t a y c o n s t a n t s i n c e t h e r e a r e no h e a t exchanges between the volume and i t s s u r r o u n d i n g s . <0' 2> i s a measure of t h e i n h o m o g e n e i t y o f th e t e m p e r a t u r e f i e l d and i t i s e x p e c t e d t o d e c r e a s e w i t h t i m e due t o t h e m i x i n g e f f e c t of m o l e c u l a r d i f f u s i o n . From e q u a t i o n ( I V . 1 1 ) , one can d e r i v e a t i m e s c a l e w h i c h d e s c r i b e s t h e r a t e a t w h i c h t h e temper-a t u r e d i f f e r e n c e s w i t h i n the f l u i d a r e b e i n g d i s s i p a t e d by m o l e c u l a r p r o c e s s e s : < e* 2 > 2 % < ( V 0 1 ) 2 > ( I V ' 1 2 ) I n e q u a t i o n ( I V . 1 2 ) , t h e t e m p e r a t u r e v a r i a n c e i s an easy p a r a m e t e r t o measure, u s i n g f o r example a s t a n d a r d STD p r o b e . M e a s u r i n g the f u l l g r a d i e n t v a r i a n c e however i s a more d i f f i c u l t t a s k s i n c e a v e r y h i g h s p a t i a l r e s o l u t i o n has t o be a t t a i n e d and s i n c e t h e g r a d i e n t v a r i a n c e may o c c u r i n t e r m i t t e n t l y and a t l o c a t i o n s w h i c h a r e dangerous f o r t h e p r o b e s t o sample (nea r t h e bottom o r the s i d e s o f Howe Sound i n t h i s c a s e ) . M o r e o ver, f r e e - f a l l i n g m i c r o s t r u c t u r e p robes measure o n l y t h e v e r t i c a l component of t h e t e m p e r a t u r e g r a d i e n t . An a t t e m p t can s t i l l be made t o match some of t h e d a t a o b t a i n e d by the Pumpkins i n the Deep Water of Howe Sound and o t h e r i n f o r m a t i o n coming from o c e a n o g r a p h i c d a t a . The Deep Water o f Howe Sound appears t o have undergone no s i g n i f i c a n t change i n i t s mean t e m p e r a t u r e between November 1973 and J a n u a r y 1974. D u r i n g t h a t p e r i o d , b o t t l e c a s t measurements showed t h a t t h e maximum t e m p e r a t u r e d i f f e r e n c e f ound w i t h i n t h e Deep Water d e c r e a s e d f r o m 0.5 C° t o 0.17 C°. T h i s s u g g e s t s a m i x i n g t i m e s c a l e of about t h r e e months ( t a k i n g f o r g r a n t e d an e x p o n e n t i a l decay) and t h u s : T ^ 10^ sec The maximum t e m p e r a t u r e d i f f e r e n c e i n F e b r u a r y 1974 was p r o b a b l y c l o s e t o 0.2 C° and t h i s s u g g e s t s t h a t : < 6' 2 > 0.01 (C°) 2 E q u a t i o n (IV.10) t h e n r e q u i r e s t h a t on t h e a v e r a g e , the l e v e l o f g r a d i e n t v a r i a n c e f o u n d i n t h e Deep Water be: < ( V 0 ' ) 2 > ^ 3 x 1 0 " 3 (C°/m) 2 T h i s v a l u e i s c l o s e t o the rms n o i s e l e v e l o f t h e Pumpkin's g r a d i e n t s i g n a l . However, due t o t h e p a t c h i n e s s o f t h e g r a d i e n t v a r i -ance d i s t r i b u t i o n , such a mean v a l u e s h o u l d g i v e r i s e t o e a s i l y o b s e r -v a b l e p a t c h e s ( f r o m the p o i n t o f v i e w o f the s e n s i t i v i t y o f the i n s t r u m e n t s ) . Drops 7 and 8 ( f i g . 3 0 and 31, F e b r u a r y 1974) show p a t c h e s o f about 10 m t h i c k n e s s and w i t h mean square g r a d i e n t v a l u e s o f a t l e a s t 10 t o 20 (C°/m) 2 w i t h i n the p a t c h e s . C o r r e c t i n g f o r t h e f r e q u e n c y r e s p o n s e o f t h e p r o b e s would i n c r e a s e t h i s v a l u e ; a v e r a g i n g o v e r the Deep Water w a t e r column would r e d u c e i t a l t h o u g h o t h e r p a t c h e s c o u l d w e l l e x i s t e l s e w h e r e w i t h i n t h e Deep Water. I n terms of o r d e r s o f magnitude, i t seems t h a t the Pumpkin o b s e r v a t i o n s show some c o n s i s t e n c y w i t h t h e b o t t l e c a s t t i m e s e r i e s i n t h e Deep Water as i n t e r p r e t e d i n t h e l i g h t o f e q u a t i o n ( I V . 1 2 ) . What i s m i s s i n g now i s a more complete coverage o f t h e o c c u r r e n c e o f t e m p e r a t u r e g r a d i e n t v a r i a n c e w i t h i n t h e I n n e r B a s i n and a h i g h e r s p a t i a l r e s o l u t i o n f o r t h e p r o b e s . Chapter V V . l Introduction. This chapter presents 21 de t a i l e d p r o f i l e s of temperature microstructure obtained i n Howe Sound. They have been selected so as to present structures which are t y p i c a l of those found i n the d i f f e r e n t regions of the water column presented i n chapters T i l and IV. They are discussed i n terms of h o r i z o n t a l extent, r e l a t i o n -ship between f i n e structure and microstructure, and possible causes for t h e i r existence. When two probes have been used simultaneously, the r e s u l t -ing p r o f i l e s are shown side by side. The usual sign convention i s used to l a b e l the scale of the v e r t i c a l temperature gradient (p o s i t i v e gradient when temperature increases upwards). Notice however that, due to an inconsistency during the data processing, p o s i t i v e values are plotted on the l e f t side of zero gradient and are l a b e l l e d accordingly. 45 V.2 D e t a i l e d p r o f i l e s . A) November 1973 p r o f i l e s : F i g u r e s 21 t o 24 show segments o f Drops 12 and 13. These dr o p s were made a t s t a t i o n Howe 4 on November 21, 1973. The o v e r a l l p r o f i l e s o f Drop 12 and 13 a r e p r e s e n t e d i n f i g . 16 and 17 and the depths from w h i c h t h e d e t a i l e d p r o f i l e have been t a k e n a r e i n d i c a t e d on them. I n f i g . 21 ( f r o m Drop P-12) t h e t e m p e r a t u r e i n c r e a s e s down-wards i n two " s t e p s " o f about 0.1 and 0.15 C°. The t e m p e r a t u r e changes t a k e p l a c e o v e r v e r t i c a l d i s t a n c e s o f 0.2 t o 0.4 m. Between th e two s t e p s , t e m p e r a t u r e f l u c t u a t i o n s w i t h an rms a m p l i t u d e o f about 0.01 C° o c c u r a t s c a l e s s m a l l e r t h a n 0.1m. I t i s t h e s e s m a l l s c a l e t e m p e r a t u r e f l u c t u a t i o n s r a t h e r t h a n t h e t e m p e r a t u r e " s t e p s " w h i c h g i v e r i s e t o the f l u c t u a t i o n s o f t h e t e m p e r a t u r e g r a d i e n t . The g r a d i e n t f l u c t u a t i o n s form a " p a t c h " w h i c h e x t e n d s from one tempera-t u r e s t e p t o t h e o t h e r . W i t h i n t h e " p a t c h " , the g r a d i e n t s i g n a l r e a c h e s peak v a l u e s o f 2 C°/m o r more. The peaks a r e about e q u a l l y d i s t r i b u t e d between p o s i t i v e and n e g a t i v e v a l u e s . I n f i g . 2 2 ( a l s o from Drop P-12) t h e t e m p e r a t u r e d e c r e a s e s w i t h i n c r e a s i n g d e p t h i n an i r r e g u l a r f a s h i o n . A t t h e bottom o f t h i s d e c r e a s e , t h e r e i s a s m a l l t e m p e r a t u r e jump. As i n f i g . 2 1 , most of t h e g r a d i e n t v a r i a n c e i s a s s o c i a t e d w i t h t e m p e r a t u r e f l u c t u a t i o n s a t s c a l e s s m a l l e r t h a n 0.1m. I n t h e upper h a l f o f f i g . 2 2 , t h e peak v a l u e s o f t h e g r a d i e n t s i g n a l have m o s t l y the same s i g n as t h a t o f t h e mean g r a d i e n t . T h i s i s i n c o n t r a s t w i t h what i s seen i n t h e l o w e r p a r t of f i g . 22 and t h r o u g h o u t f i g . 21. The s m a l l t e m p e r a t u r e jump l o c a t e d n e a r t h e b ottom of f i g . 22 i s a s s o c i a t e d w i t h c o m p a r a t i v e l y l i t t l e g r a d i e n t v a r i a n c e . F i g . 23 comes from a r e g i o n o f Drop 13 w h i c h p r e s e n t s many a b r u p t t e m p e r a t u r e changes (see f i g . 1 7 ) . Near 37 m, a 0.05 C° change o c c u r s w i t h a 0.5 C°/m h i g h , 0.12 m t h i c k g r a d i e n t p u l s e . Near 38 m, a t e m p e r a t u r e change w i t h a s i m i l a r magnitude i s accompanied by a c l u s t e r o f g r a d i e n t s p i k e s p e a k i n g a t 1.5 t o 2 C°/m and w i t h t h i c k n e s s e s s m a l l e r t h a n 0.05 m. Near 38.7 m a 0.06 C° t e m p e r a t u r e s t e p i s accom-p a n i e d by a s i n g l e g r a d i e n t s p i k e w h i c h peaks a t more t h a n 3 C°/m ( t h e maximum v a l u e w h i c h c o u l d be p l o t t e d h e r e ) . I n t h e s e examples, most o f the g r a d i e n t peak v a l u e s have t h e same s i g n as t h a t of t h e l o c a l mean g r a d i e n t ( a v e r a g e d o v e r i n t e r v a l s of one o r two m e t r e s ) . F i g . 24 p r e s e n t s a r e g i o n o f Drop 13 where t h e t e m p e r a t u r e d e c r e a s e s w i t h depth i n two ramps, each about 1.5 m t h i c k , s e p a r a t e d f r o m each o t h e r by a n e a r l y i s o t h e r m a l l a y e r a l s o about 1.5 m t h i c k . F l u c t u a t i o n s i n t e m p e r a t u r e o c c u r m a i n l y a t s c a l e s o f 0.1 m o r l e s s . A t t h e s e s m a l l s c a l e s , t h e r e a r e many t e m p e r a t u r e i n v e r s i o n s ( w i t h r e s p e c t t o t h e main t r e n d ) . A l l the l a r g e g r a d i e n t peaks have t h e same s i g n as t h e mean g r a d i e n t . The mean g r a d i e n t t h r o u g h t h e ramps i s about 0.077 C°/m w h i l e t h e r.m.s. g r a d i e n t ( u n c o r r e c t e d f o r t h e l i m i t e d r e s p o n s e o f t h e p r o b e s ) i s about 0.2 C°/m, 2\ t i m e s l a r g e r . I n summary, th e m i c r o s t r u c t u r e p r o f i l e s o f November 1973 show t h a t the a b r u p t t e m p e r a t u r e changes w h i c h were seen i n t h e o v e r a l l p r o f i l e s t a k e p l a c e o v e r v e r t i c a l d i s t a n c e s of 0.1 t o 2 m e t r e s i n many c a s e s . The t e m p e r a t u r e changes o c c u r e i t h e r as a b r u p t jumps ( " s t e p s " ) , as r e g i o n s of l a r g e t e m p e r a t u r e f l u c t u a t i o n s o r as r e g i o n s where t h e d e t a i l e d p r o f i l e i s smooth and a l m o s t l i n e a r ("ramps"). The v a r i a n c e i n t h e t e m p e r a t u r e g r a d i e n t w h i c h i s o b s e r v e d i n t h e o v e r a l l p r o f i l e s may be caused by s i n g l e s p i k e s , a c l u s t e r i n g o f s p i k e s w h i c h have m o s t l y t h e same s i g n , o r p a t c h e s of f l u c t u a t i o n s where t h e g r a d i e n t has peaks about e q u a l l y d i s t r i b u t e d between p o s i t i v e and n e g a t i v e v a l u e s . The magnitude o f a t e m p e r a t u r e change seems p o o r l y r e l a t e d t o t h e magnitude of t h e g r a d i e n t v a r i a n c e t h a t goes w i t h i t , i f i t i s r e l a t e d a t a l l . B) Outer B a s i n , F e b r u a r y 1974. Three d e t a i l e d p r o f i l e s t a k e n f r o m Drop 6 ( F e b r u a r y 1974) a r e p r e s e n t e d h e r e . Drop 6 was made i n R a m i l l i e s C h a n n e l ( O u t e r B a s i n ) . I t s o v e r a l l p r o f i l e i s p r e s e n t e d i n f i g . 29 and the l o c a t i o n o f t h e d e t a i l e d p r o f i l e s i s shown on i t . F i g . 41 p r e s e n t s a l o c a l t e m p e r a t u r e maximum fo u n d n e a r a depth o f 57 m i n Drop 6. A t t h e top of t h e warmer l a y e r , t h e tempera-t u r e change t a k e s p l a c e t h r o u g h s t e p s of 0.1 t o 0.2 C°, 0.2 t o 0.5 m t h i c k . S t e p s were f o u n d by b o t h p r o b e s a l t h o u g h t h e d e t a i l s o f t h e s t e p s d i f f e r on each p r o f i l e . I n t h e g r a d i e n t s i g n a l , t h e s t e p s t r a n s l a t e i n t o s p i k e s p e a k i n g a t more th a n 3 C°/m (and i n some c a s e s a t more th a n 4.5 C°/m, t h e l i m i t o f t h e d i g i t i z e r ) . I n t h e s i g n a l , the s p i k e s a r e t h i n n e r t h a n 0.05 m. I n t h e o v e r a l l p r o f i l e o f Drop 6 ( f i g . 2 9 ) , t h e s e few s p i k e s g i v e r i s e t o one o f t h e l a r g e s t r.m.s. g r a d i e n t " p a t c h " o f t h i s d r o p . A t t h e bottom o f t h e warmer l a y e r (between d e p t h s o f 59 and 60 m, where t e m p e r a t u r e d e c r e a s e s downwards), t h e t e m p e r a t u r e p r o f i l e t a k e s t h e shape of a smooth "ramp". The g r a d i e n t s i g n a l c o n s i s t s o f " r i p p l e s " w i t h a wave l e n g t h o f about 0.05 m and an a m p l i t u d e o f about 0.2 C°/m. I n p r o f i l e B, on t h e r i g h t o f f i g u r e 41, j u s t above t h e t e m p e r a t u r e "ramp", t h e r e i s a p a t c h o f h i g h wave number g r a d i e n t f l u c t u a t i o n s . The g r a d i e n t peaks a r e about e q u a l l y d i s t r i b u t e d between p o s i t i v e and n e g a t i v e v a l u e s . The r.m.s. v a l u e of t h e g r a d i e n t i s 0.4 C°/m ( u n c o r r e c t e d ) and the p a t c h i s 0.75 m t h i c k . Y e t t h e g r a d i e n t s i g n a l i n t e g r a t e s i n t o a n e t t e m p e r a t u r e change o f o n l y 0.02 C° a c r o s s the p a t c h . I t i s i n t e r e s t i n g t o n o t i c e t h a t no such p a t c h i s found i n p r o f i l e A. F i g u r e 42 shows the d e t a i l o f a l a r g e m i c r o s t r u c t u r e p a t c h found i n Drop 6 n e a r 70 m. I n t h e o v e r a l l p r o f i l e o f Drop 6 ( f i g . 2 9 ) , t h e two p a t c h e s a r e o f f s e t i n d e p t h by about 3 m. I n f i g u r e 42, t h e t e m p e r a t u r e s t e p s have been r e a l i g n e d i n o r d e r t o f a c i l i t a t e c o m p a r i -sons. A t s c a l e s of 1 m o r l e s s , the two t e m p e r a t u r e p r o f i l e s b e a r l i t t l e r e semblance t o each o t h e r . More t e m p e r a t u r e f l u c t u a t i o n s a t s c a l e s s m a l l e r t h a n 0.1 m a r e found i n p r o f i l e A t h a n i n p r o f i l e B. The a m p l i t u d e of t h e t e m p e r a t u r e f l u c t u a t i o n s i s comparable t o t h e t e m p e r a t u r e d i f f e r e n c e f ound a c r o s s t h e " p a t c h " . The g r a d i e n t s i g n a l peaks a t v a l u e s l a r g e r t h a n 3 C /m, on b o t h s i g n s . The p a t c h of p r o -f i l e A c o n t a i n s s e v e r a l t i m e s more g r a d i e n t v a r i a n c e t h a n t h a t o f p r o f i l e B. I n f i g u r e 43, t h e l a s t p a i r o f d e t a i l e d p r o f i l e s t o be p r e s e n t e d i n Drop 6, p r o f i l e A shows a l a r g e p a t c h o f g r a d i e n t f l u c -t u a t i o n s w h i c h i s n o t f o u n d a t a l l i n p r o f i l e B. M o r e o v e r , t h e t e m p e r a t u r e p r o f i l e s a r e a l t o g e t h e r d i f f e r e n t : p r o f i l e A p r e s e n t s a t e m p e r a t u r e maximum w h i c h i s n o t found i n p r o f i l e B. The two p r o b e s were s e p a r a t e d h o r i z o n t a l l y by 10 t o 30 m and probe B, s i n k i n g s l i g h t l y s l o w e r t h a n probe A d u r i n g t h i s d r o p , r e a c h e d the d e p t h o f the p a t c h some 40 seconds l a t e r t h a n probe A. I t was n o t e d i n C h a p t e r IV t h a t t e m p e r a t u r e s t r u c t u r e s a,t s c a l e s o f 2 m o r l e s s o f t e n do n o t c o r r e s p o n d on two p r o f i l e s o f a p a i r . Here, the d e t a i l e d p r o f i l e s p r e s e n t i n s t a n c e s where t h e t y p e o f m i c r o s t r u c t u r e i s the same on b o t h p r o f i l e s ( f o r i n s t a n c e on t h e upper and l o w e r s i d e s o f t h e t e m p e r a t u r e maximum n e a r 55 m). I n o t h e r i n s t a n c e s , t h e r e were l a r g e d i f f e r e n c e s i n t h e t y p e o f m i c r o -s t r u c t u r e as w e l l as i n the amount of g r a d i e n t v a r i a n c e o b s e r v e d , f o r i n s t a n c e , n e a r 58 m. Near 105 m, a l a r g e p a t c h o f g r a d i e n t v a r i a n c e was f o u n d i n one p r o f i l e w h i l e none was f o u n d i n t h e o t h e r . A t t h a t d e p t h , s l i g h t d i f f e r e n c e s c o u l d a l s o be found i n t h e l o c a l w a t e r t y p e s . 50 C) F e b r u a r y 1974, I n t e r m e d i a t e Water ( I n n e r B a s i n ) . E l e v e n s e t s o f d e t a i l e d p r o f i l e s o b t a i n e d i n t h e I n t e r m e d -i a t e Water of t h e I n n e r B a s i n a r e p r e s e n t e d h e r e . A v a r i e t y of s t r u c t u r e s found i n Drops 7, 8 and 9 ( s t a t i o n Howe 4) can be t r a c e d from one p r o f i l e t o t h e n e x t . Drop 10 p r e s e n t s a f i n e s t r u c t u r e and a m i c r o s t r u c t u r e w h i c h i s d i f f e r e n t enough from t h a t of the o t h e r d r o p s t o d e s e r v e s p e c i a l a t t e n t i o n . Drop 7 I n the o v e r a l l p r o f i l e o f Drop 7 ( f i g . 3 0 ) , t h e r e g i o n l o c a t e d between 10 and 40 m p r e s e n t s v e r y l i t t l e g r a d i e n t v a r i a n c e . Y e t , when s m a l l p a t c h e s a r e f o u n d , t h e y show on each p r o f i l e of t h e p a i r . F i g u r e 44 comes from. 28 t o 34 m and g i v e s a c l o s e r l o o k a t t h e s e s t r u c t u r e s . I t shows t h a t d e t a i l s as s m a l l as 0.2 m i n t h e tem-p e r a t u r e p r o f i l e can be seen on b o t h p r o f i l e s (see f o r i n s t a n c e n e a r 30 m). I t i s i n t e r e s t i n g t o n o t i c e the p r e s e n c e of a number of t e m p e r a t u r e i n v e r s i o n s ( w i t h r e s p e c t t o the main t r e n d ) a t s c a l e s s m a l l e r t h a n 0.5 m. These a r e n o t n o t i c e a b l e i n t h e o v e r a l l p r o f i l e s . I t i s a l s o o f i n t e r e s t t o n o t i c e t h a t t h e g r a d i e n t peaks w h i c h g i v e r i s e t o t h e v a r i a n c e p a t c h e s a r e f o u n d where t h e r e a r e a b r u p t temper-a t u r e i n c r e a s e s ( i n the downwards d i r e c t i o n ) . F i g u r e s 45 and 46 show two a b r u p t t e m p e r a t u r e changes t h a t o c c u r i n Drop 7 n e a r 43 and 53 m (see o v e r a l l p r o f i l e ) . F i g . 45 shows t h a t each probe sensed a d i f f e r e n t m i c r o s t r u c t u r e a t t h e t e m p e r a t u r e s t e p . I n p r o f i l e A, t h e r e i s a p a t c h o f g r a d i e n t s p i k e s w i t h m o s t l y the sign as the mean gradient. In p r o f i l e B, the temperature change occurs through only two large gradient spikes. Just a few cm above i t , however, there are gradient f l u c t u a t i o n s about a zero mean. Near 4 6 m, there i s a temperature change with no s i g n i f i c a n t gradient variance. In f i g . 4 6 , the temperature steps of both probes are accom-panied by a gradient s i g n a l which consists of several spikes with magnitudes of more than 4 C°/m. Most of the temperature change occurs within 0 . 2 m. Below 5 4 m, the temperature increases i r r e g u l a r l y but monotonously downwards. The gradient s i g n a l presents no large peaks. No temperature inversion (with respect to the main trend) i s observed even at the smallest scales. Between 5 5 and 5 9 m, the mean gradient i s - 0 . 0 . 4 4 C ° / m while the r.m.s. gradient i s about 0 . 0 9 C°/m (a factor of three above the noise l e v e l ) . Figures 4 4 , 4 5 and 4 6 are t y p i c a l of three regions of Drop 7 which are outlined i n the o v e r a l l p r o f i l e to f i g . 3 0 and c a l l e d "layer A", "layer B" and "layer C". These regions of the water column are examined again i n Drops 8 and 9 . Drop 8 Two d e t a i l e d p r o f i l e s taken from Drop 8 are presented here ( f i g . 4 7 and 4 8 ) . Drop 8 was made one hour a f t e r Drop 7 and within one km of the p o s i t i o n of Drop 7 . The o v e r a l l p r o f i l e of Drop 8 shares many features with that of Drop 7 . F i g . 47 comes from 19 t o 26 m. Two main t e m p e r a t u r e changes a r e seen on each p r o f i l e ( n e a r 20 and 23.5 m). Near 20 m, a s m a l l t e m p e r a t u r e i n v e r s i o n i s a l s o o b s e r v e d i n b o t h p r o f i l e s . I n t h i s r e g i o n of the w a t e r column, t h e mean g r a d i e n t i s about 0.01 C°/m. Two t e m p e r a t u r e s t e p s a c c o u n t f o r one t h i r d t o one h a l f o f t h i s . Between t h e s t e p s , t h e mean g r a d i e n t s t a y s c l o s e t o 0.005 t o 0.001 C°/m and a number o f m i n o r t e m p e r a t u r e s t e p s s t i l l a c c o u n t f o r much of t h i s t r e n d . A t each m a j o r t e m p e r a t u r e s t e p , t h e r e i s a g r a d i e n t p u l s e . The p u l s e s a c c o u n t f o r most o f the g r a d i e n t v a r i a n c e . A t 24 m, below a g r a d i e n t p u l s e , t h e r e a r e a l s o some g r a d i e n t f l u c t u a t i o n s w h i c h form a s o r t of low a m p l i t u d e " p a t c h " on b o t h t r a c e s . F i g . 48 comes from between 50 and 58 m. I t p r e s e n t s two l a r g e t e m p e r a t u r e changes s e p a r a t e d by a l o c a l t e m p e r a t u r e maximum and a minimum. The t e m p e r a t u r e l a y e r i n g o f t h i s f i g u r e i s v e r y s i m i l a r t o t h a t w h i c h was found i n Drop 7 a t s i m i l a r d e p t h (see f i g . 45 and 4 6 ) . What i s m i s s i n g h e r e i s a n e a r l y i s o t h e r m a l l a y e r w h i c h , i n Drop 7, was f o u n d between 47 and 52 m ( t h e t e m p e r a t u r e minimum). G r a d i e n t s p i k e s a r e found as i n Drop 7. H e r e , most of t h e t e m p e r a t u r e changes o c c u r w i t h i n one metre i n s t e a d of 0.2 m i n Drop 7. N o t i c e t h a t t h e t e m p e r a t u r e s t e p o f p r o f i l e B ( r i g h t hand s i d e ) c o n s i s t s i n f a c t o f two c l o s e l y spaced b u t d i s t i n c t s t e p s . Such " s p l i t t i n g " of t e m p e r a t u r e s t e p s can a l s o be found i n Drops 6 and 7, i n a l e s s pronounced f a s h i o n . Drop 9. Drop 9 was also made at s t a t i o n Howe 4, i n the v i c i n i t y of Drops 7 and 8 and one hour a f t e r Drop 8. The o v e r a l l p r o f i l e i s presented i n f i g . 32. Four d e t a i l e d p r o f i l e s taken from Drop 9 are presented here. F i g . 49 presents the deta i l e d p r o f i l e between 28 and 35 m, the same depth range as f i g . 44 from Drop 7. A patch of gradient variance occurs between 32.5 and 34 m, within a l o c a l temperature mini-mum. At 32.5 m, there i s a 0.2 m thick region where the temperature decreases downwards. I t i s accompanied by only a low amplitude grad-ient pulse. The most i n t e r e s t i n g aspect of f i g . 49 i s the s t r i k i n g resemblance that i t presents to f i g . 44 of Drop 7. Most temperature changes of one fig u r e can be paired with s i m i l a r ones i n the other and the absolute values of the temperatures are very close. This gives the impression that the d e t a i l s of the temperature p r o f i l e s may extend much farther than the spacing of the two probes i n a double p r o f i l e and much longer than several hours. Figures 50 and 51 come from a region of the water column where Drops 7 and 8 presented two large temperature changes separated by a minor maximum and minimum. Drop 9 presents the same " f i n e structure" but i n a d i s t o r t e d fashion. In f i g . 50, the upper side of the temperature maximum consists of a "ramp" rather than a temperature step. The bottom of the temperature maximum i s very smooth and the corresponding gradient s i g n a l has a unique aspect. Most of the grad-ient variance i s associated with the patch located on the ramp where t h e mean t e m p e r a t u r e i n c r e a s e s w i t h d e p t h . F i g u r e 51 p r e s e n t s t h e second t e m p e r a t u r e s t e p . H e r e , i t c o n s i s t s o f a m i x t u r e o f ramp and s t e p on b o t h d e t a i l e d p r o f i l e s . N o t i c e t h a t on t r a c e A, t h e t e m p e r a t u r e s t e p g i v e s r i s e t o a s i n g l e g r a d i e n t s p i k e w h i c h a c c o u n t s f o r most o f the g r a d i e n t v a r i a n c e of t h i s r e g i o n o f t h e w a t e r column. D u r i n g t h e p r o c e s s i n g o f t h e d a t a , i t was n o t c l e a r a t f i r s t whether t h i s s p i k e was r e a l o r s p u r i o u s d a t a . T r a c e B showed t h a t i t was r e a l ( a l t h o u g h t h e two t e m p e r a t u r e s t e p s a r e p r e s e n t e d s i d e by s i d e , t h e y were sensed a t s l i g h t l y d i f f e r e n t t i m e s and c o u l d n o t a r i s e from a common s o u r c e o f s p u r i o u s s i g n a l ) . F i g . 52 p r e s e n t s a d e t a i l e d p r o f i l e f r o m t h e depth range o f 65 t o 72 m. A mean g r a d i e n t o f about 0.02 C°/m e x i s t s a c r o s s t h e p r o -f i l e . I t compares t o t h e l o w e r p a r t o f f i g . 46 (Drop 7 ) . The r.m.s. g r a d i e n t i s about 0.05 C°/m. F i g . 52 shows t h e a s p e c t o f t e m p e r a t u r e m i c r o s t r u c t u r e where a s i g n i f i c a n t mean g r a d i e n t e x i s t s b u t v e r y l i t t l e g r a d i e n t v a r i a n c e i s fo u n d . N o t i c e t h e p r e s e n c e o f a s p u r i o u s d a t a p o i n t n e a r 57.5 m. I t s e f f e c t i n t h e t e m p e r a t u r e p r o f i l e i s n e g l i -g i b l e b u t i t s e f f e c t on e s t i m a t e s o f the g r a d i e n t v a r i a n c e c o u l d have been l a r g e i f i t had gone u n n o t i c e d . Drop 10 F i g u r e s 53 and 54 p r e s e n t t h e m i c r o s t r u c t u r e o f Drop 10 ( s t a t i o n Howe 4.7 i n t h e I n n e r B a s i n ) between 29 and 54 m. N o t i c e t h a t t h e depth s c a l e has been compressed by a f a c t o r o f two compared w i t h t h a t o f p r e v i o u s d e t a i l e d p r o f i l e s . The p r o f i l e o f f i g . 54 f o l l o w s i m m e d i a t e l y t h a t o f f i g . 53. The de p t h l e v e l o f 42 m i s th u s o c c u p i e d by a l a y e r o f maximum t e m p e r a t u r e w h i c h i s about one metre t h i c k . A t the t o p o f f i g . 53, t h e r e i s a v e r y smooth, l o g a r i t h m i c -l i k e t e m p e r a t u r e p r o f i l e about 3 m t h i c k (between 29 and 32 m). I t i s accompanied by no s i g n i f i c a n t g r a d i e n t m i c r o s t r u c t u r e e x c e p t f o r a b r o a d , low a m p l i t u d e " p u l s e " . T h i s i s a u n i q u e o c c u r r e n c e i n t h e Howe Sound m i c r o s t r u c t u r e d a t a . Between 32 and 36 m, t h e r e i s a n o t h e r l a y e r w i t h a somewhat s i m i l a r t e m p e r a t u r e p r o f i l e b u t a v e r y d i f f e r e n t m i c r o s t r u c t u r e . H e r e , a c o m p a r a t i v e l y l a r g e amount of g r a d i e n t v a r i -ance o r i g i n a t e s i n f l u c t u a t i o n s a t s c a l e s s m a l l e r t h a n 0.1 m. T h i s v a r i a n c e has a d i f f e r e n t s p a t i a l d i s t r i b u t i o n w i t h i n each p r o f i l e . Through t h e l a y e r , t h e r e i s a l s o a s i g n i f i c a n t mean g r a d i e n t and a number of m i n o r , h i g h wave number g r a d i e n t s p i k e s . Other l a y e r s i n f i g . 53 p r e s e n t l i t t l e g r a d i e n t v a r i a n c e and the f l u c t u a t i o n s t a k e m o s t l y t h e s i g n o f the l o c a l mean g r a d i e n t . I n f i g . 54, o t h e r l a y e r s 1 t o 3 m t h i c k a r e a l s o f o u n d . Two of them ( a t 45 and 51 m) a r e f a i r l y i s o t h e r m a l w h i l e t h e o t h e r s p r e -s e n t a mean g r a d i e n t . The g r a d i e n t s i g n a l c o n s i s t s m o s t l y o f s p i k e s w h i c h have t h e s i g n o f t h e mean g r a d i e n t . Near 49 m, a l a r g e g r a d i e n t s p i k e i s c o n s i d e r e d t o be t h e r e s u l t o f a s p u r i o u s d a t a p o i n t . The m i c r o s t r u c t u r e o f t h e I n t e r m e d i a t e Water o f Drop 10 th u s c o n s i s t s o f rounded t e m p e r a t u r e s t e p s (compared t o t h o s e o f Drops 7 and 8) w h i c h a r e accompanied by "one s i d e d " g r a d i e n t f l u c t u a t i o n s . Most o f t h e l a y e r s a r e n o t even a p p r o x i m a t e l y i s o t h e r m a l . D e t a i l s s m a l l e r t h a n 0.5 m i n t h e t e m p e r a t u r e p r o f i l e s a r e u s u a l l y n o t i d e n t i f i e d i n b o t h p r o f i l e s a t once. The l a y e r s t h e m s e l v e s a r e always found i n b o t h p r o f i l e s and i t i s c l e a r t h a t t h e y e x t e n d o v e r d i s t a n c e s l a r g e r t h a n about 20 m l a t e r a l l y . As was men t i o n e d i n C h a p t e r I V , STD p r o f i l e s i n d i c a t e t h a t t h i s s o r t o f s t r u c t u r e c o u l d have been found i n much of t h e I n n e r B a s i n ' s I n t e r m e d i a t e Water. However, Drop 10 i s t h e o n l y one i n w h i c h t h e probes worked b e s i d e s t h e o t h e r drops made a t s t a t i o n Howe 4 and i n t h e Outer B a s i n . Summary I n t h e I n t e r m e d i a t e Water, Drops 7, 8 and 9 p r e s e n t a s i m i -l a r f i n e and m i c r o s t r u c t u r e . C o m p a r a t i v e l y l a r g e t e m p e r a t u r e s t e p s a r e found i n a l l t h r e e p r o f i l e s between 45 and 55 m. The v e r t i c a l sequence o f t e m p e r a t u r e l a y e r s between t h e s e s t e p s i s s i m i l a r i n t h e t h r e e p r o f i l e s a l t h o u g h t h e t h i c k n e s s o f i n d i v i d u a l l a y e r s , i f t h e y a r e t h e same ones, v a r i e s by s e v e r a l m e t r e s . Drops 7, 8 and 9 a l s o have s i m i l a r v e r t i c a l t e m p e r a t u r e sequences i n t h e 15 t o 45 m range and s u g g e s t t h a t s t r u c t u r e s 1 t o 3 m t h i c k may re m a i n r e c o g n i z a b l e o v e r p e r i o d s o f a t l e a s t s e v e r a l h o u r s and o v e r d i s t a n c e s much l o n g e r t h a n t h e n o m i n a l 20 m w h i c h s e p a r a t e ' t h e two pr o b e s i n any g i v e n p r o f i l e . Most o f t h e g r a d i e n t v a r i a n c e found i n t h e I n t e r m e d i a t e Water of t h e I n n e r B a s i n i s a s s o c i a t e d w i t h t h e g r a d i e n t s p i k e s c o n -n e c t e d t o t h e l a r g e t e m p e r a t u r e s t e p s f o u n d between 45 and 55 m. Other minor p a t c h e s o f g r a d i e n t v a r i a n c e r e s u l t from s m a l l groups o f low a m p l i t u d e g r a d i e n t s p i k e s w h i c h o c c u r n e a r the minor t e m p e r a t u r e s t e p s . These patches are usually seen on both p r o f i l e s of a p a i r and seem to extend l a t e r a l l y further than the nominal 20 m probe separation. In the temperature p r o f i l e s , d e t a i l s as th i n as 0.2 m can be i d e n t i f i e d at once on both p r o f i l e s of a p a i r . The f i n e structure of Drop 10 d i f f e r s markedly from that of Drops 7, 8 and 9. I t presents numerous layers and several temperature maxima and minima. Most layers are not isothermal and the temperature steps which separate them are rounded compared to those of the preced-ing drops. Gradient variance a r i s e s mostly from "one sided" gradient f l u c t u a t i o n s , as i n the previous drops. D) Inner Basin Deep Water (February 1974). Three deta i l e d p r o f i l e s from the Deep Water are presented here. The f i r s t two, f i g . 55 and 56, show a microstructure patch found i n Drop 7 between 130 and 150 m. The other p r o f i l e shows a patch found i n Drop 8 near 105 m. The depth scale of the p r o f i l e s i s the same one which was used f o r Drop 10. Through f i g . 55 and 56, the temperature p r o f i l e s of both probes present an "S" shape. This i s also v i s i b l e i n the o v e r a l l pro-f i l e of Drop 7 with a magnified temperature scale ( f i g . 34). The d e t a i l s of each p r o f i l e of the p a i r d i f f e r s i g n i f i c a n t l y at scales smaller than 3m. For instance, i n p r o f i l e B the downwards temperature increase takes place i n a-graded fashion over 2.5 m. In p r o f i l e A, the same temperature increase takes place i n one single step where the g r a d i e n t peaks a t more t h a n 4.5 C /m. The g r a d i e n t v a r i a n c e a s s o c i -a t e d w i t h t h e s p i k e o f p r o f i l e A i s o f t h e same o r d e r o f magnitude as the v a r i a n c e a s s o c i a t e d w i t h t h e c o r r e s p o n d i n g p a t c h i n p r o f i l e B. Many o t h e r d i f f e r e n c e s a r e a l s o found i n the t h i c k n e s s o f f e a t u r e s t h a t can be i d e n t i f i e d on b o t h p r o f i l e s . F i g . 57 shows a m i c r o s t r u c t u r e p a t c h w h i c h i s found between 100 and 110 m i n Drop 8, w i t h i n a s l i g h t t e m p e r a t u r e minimum ( s e e t h e o v e r a l l p r o f i l e w i t h a m a g n i f i e d t e m p e r a t u r e s c a l e o f f i g . 3 5 ) . The te m p e r a t u r e d i f f e r e n c e s f o u n d h e r e a r e s m a l l compared t o what has been found i n o t h e r d r o p s (about 0.01 C° h e r e ) . The g r a d i e n t a l s o peaks a t c o m p a r a t i v e l y l ow v a l u e s ( t y p i c a l l y 1 C°/m). Much of t h e g r a d i e n t v a r i a n c e i s a s s o c i a t e d w i t h s c a l e s s m a l l e r t h a n 0.05 m and t h e g r a d i e n t peak v a l u e s a r e d i s t r i b u t e d about e q u a l l y between p o s i t i v e and n e g a t i v e v a l u e s . E x c e p t f o r a few p a t c h e s , t h e Deep Water o f Howe Sound p r e s e n t s v e r y l i t t l e g r a d i e n t v a r i a n c e . When t e m p e r a t u r e d i f f e r e n c e s a r e p r e s e n t , t he two pr o b e s g i v e p r o f i l e s t h a t d i f f e r s i g n i f i c a n t l y a t s c a l e s l o w e r t h a n 2 or 3m. I t i s i n t e r e s t i n g t o n o t i c e t h a t between 80 and 110 m, t h e w a t e r columns o f Drops 7 t o 10 have s i m i l a r tempera-t u r e p r o f i l e s b u t t h a t o n l y Drop 8 p r e s e n t s a l a r g e p a t c h o f g r a d i e n t v a r i a n c e . V.3 D i s c u s s i o n . a) Summary of m i c r o s t r u c t u r e d e s c r i p t i o n : I n t h e p r e c e d i n g s e c t i o n , s e v e r a l e x p r e s s i o n s have been used r e p e a t e d l y f o r d e s c r i b i n g f e a t u r e s o f t h e t e m p e r a t u r e f i n e and m i c r o s t r u c t u r e . Here, a l i s t i s p r e s e n t e d . As seen from s c a l e s o f 1 t o 5 m , segments o f t h e t e m p e r a t u r e p r o f i l e s were d e s c r i b e d i n terms o f the mean t e m p e r a t u r e g r a d i e n t a c r o s s them. Here, "mean" o r " l o c a l mean" i n d i c a t e s t h a t a v e r a g i n g i s made o v e r t h a t segment. Thus t h e l o c a l mean g r a d i e n t may be a s s o c i a t e d w i t h a temporary f e a t u r e o f t h e w a t e r column o r may have a s i g n d i f f e -r e n t from t h a t o f the " o v e r a l l mean g r a d i e n t " a v e r a g e d o v e r a l a r g e p o r t i o n o f the w a t e r column. •As seen from s c a l e s of 0.5 t o 2 m , t e m p e r a t u r e m i c r o s t r u c t u r e can be d e s c r i b e d r o u g h l y i n terms o f : "Temperature s t e p s " when a t e m p e r a t u r e change t a k e s p l a c e o v e r a v e r t i c a l d i s t a n c e s m a l l e r t h a n 0.5 m ( i . e . i n f i g . 45 and 5 4 ) . "Temperature ramps" when a t e m p e r a t u r e change t a k e s p l a c e o v e r a v e r t i -c a l d i s t a n c e o f 1 m o r more i n a g r a d u a l f a s h i o n ( i . e . f i g . 4 1 ) . " i r r e g u l a r t e m p e r a t u r e change" when a t e m p e r a t u r e change t a k i n g p l a c e o v e r v e r t i c a l d i s t a n c e s l a r g e r t h a n 1 m i s accompanied by l a r g e t e m p e r a t u r e f l u c t u a t i o n s a t s m a l l e r s c a l e s ( i . e . f i g . 2 2 ) . Much o f t h e t e m p e r a t u r e g r a d i e n t m i c r o s t r u c t u r e can be d e s c r i b e d i n terms o f : - S p i k e s and p u l s e s as a r e seen, f o r i n s t a n c e , i n f i g . 41. -"one s i d e d g r a d i e n t s i g n a l " when m i c r o s t r u c t u r e c o n s i s t s o f a p a t c h o f g r a d i e n t f l u c t u a t i o n s w h i c h peak m o s t l y w i t h one s i g n a s , f o r i n s t a n c e , i n f i g . 24. - " s y m m e t r i c a l g r a d i e n t f l u c t u a t i o n s " when the g r a d i e n t f l u c t u a t i o n s p r e s e n t peaks t a k i n g b o t h s i g n s w i t h about e q u a l f r e q u e n c y a s , f o r i n s t a n c e , i n f i g . 21. V.3.b) R e l a t i o n s h i p s between t e m p e r a t u r e and t e m p e r a t u r e g r a d i e n t m i c r o s t r u c t u r e : The g r a d i e n t s i g n a l d i s p l a y e d i n the f i g u r e s i s s i m p l y t h e d e r i v a t i v e o f t h e t e m p e r a t u r e s i g n a l . Beyond t h i s r e l a t i o n s h i p , o t h e r q u e s t i o n s may be a s k e d such as: what t y p e o f g r a d i e n t m i c r o s t r u c t u r e i s f o und t o accompany such and such a ty p e o f t e m p e r a t u r e m i c r o -s t r u c t u r e o r f i n e s t r u c t u r e ? G a r g e t t (1976) has a l s o sought suc h r e l a t i o n s h i p s and some o f h e r c o n c l u s i o n s a r e me n t i o n e d below. Here a r e some o b s e r v a t i o n s w h i c h came fr o m e x a m i n i n g t h i s d a t a s e t . When t h e l o c a l mean g r a d i e n t i s n e g a t i v e ( t e m p e r a t u r e d e c r e a -s i n g u p w a r d s ) , t e m p e r a t u r e s t e p s and g r a d i e n t s p i k e s a r e o f t e n f o u n d (see f i g . 48, 50, 5 1 ) . When t h e l o c a l mean g r a d i e n t i s p o s i t i v e , t h e r e i s o f t e n l i t t l e g r a d i e n t v a r i a n c e compared w i t h t h a t f o u n d i n n e i g h b o u r i n g r e g i o n s o f t h e w a t e r column. The p r o f i l e s l o o k smoother (see f i g . 50 near 46 m). "Symmetric" p a t c h e s of s m a l l s c a l e g r a d i e n t f l u c t u a t i o n show no c l e a r p r e f e r e n c e w i t h r e s p e c t t o the s i g n o f t h e t e m p e r a t u r e g r a d i e n t (see f o r i n s t a n c e f i g . 21 and 2 3 ) . There a r e i n s t a n c e s where t h i s t y p e of p a t c h i s f ound j u s t above o r u n d e r n e a t h a t e m p e r a t u r e change ( f i g . 21, 41, 45) w h i l e i n o t h e r c a s e s , t h e p a t c h c o n s t i t u t e s t h e t e m p e r a t u r e change t h r o u g h an " i r r e g u l a r " t y p e of t e m p e r a t u r e p r o -f i l e ( f i g . 42, 43, 5 6 ) . Temperature s t e p s a r e o f t e n a s s o c i a t e d w i t h s i n g l e g r a d i e n t s p i k e s o r a s m a l l group o f them. However, i t i s o b s e r v e d t h a t t h e t e m p e r a t u r e g r a d i e n t v a r i a n c e a s s o c i a t e d w i t h t e m p e r a t u r e s t e p s cannot be p r e d i c t e d on t h e b a s i s of t h e t e m p e r a t u r e d i f f e r e n c e a l o n e . There a r e i n s t a n c e s of w i d e , low a m p l i t u d e g r a d i e n t p u l s e s as w e l l as o f s p i k e s t h i n n e r t h a n what the p r o b e s can r e s o l v e and w i t h a m p l i t u d e s h i g h e r t h a n c o u l d be r e c o r d e d by t h e p r o b e s (see f i g . 45 and 5 1 ) . F o r a g i v e n t e m p e r a t u r e change, t h e t h i n n e r i s t h e g r a d i e n t p u l s e , the l a r g e r a r e i t s a m p l i t u d e and a s s o c i a t e d v a r i a n c e . The o b s e r v a t i o n s thus i n d i c a t e t h a t t h e s i z e o f a t e m p e r a t u r e change does n o t d e t e r m i n e the w i d t h o f t h e g r a d i e n t p u l s e s t h a t a r e a s s o c i a t e d w i t h i t . V.3.c) L a t e r a l e x t e n t of m i c r o s t r u c t u r e i n Howe Sound. - G i v e n two t e m p e r a t u r e p r o f i l e s o b t a i n e d s i m u l t a n e o u s l y by two p robes s e p a r a t e d by something l i k e 10 o r 20 m, what i s t h e s i z e of the s m a l l e s t s t r u c t u r e s w h i c h can be i d e n t i f i e d on b o t h p r o f i l e s a t once? T h i s d i s c u s s i o n b e a r s on t h e F e b r u a r y 1974 d a t a s i n c e o n l y t h e n were d o u b l e p r o f i l e s made. See c h a p t e r I I I f o r d i s c u s s i o n of t h e p r o b e s ' l a t e r a l s e p a r a t i o n . I n t h e upper 100 m o f the I n n e r B a s i n ( F e b r u a r y 1 974), d e t a i l e d p r o f i l e s ( f i g . 44 t o 54) show t h a t t h e p r o f i l e s d i f f e r m o s t l y a t s c a l e s s m a l l e r t h a n 0.1 t o 0.3 m. I n o t h e r words, m i n o r tempera-t u r e maxima o r minima t h i c k e r t h a n 0.1 t o 0.3 m can be i d e n t i f i e d on b o t h p r o f i l e s of p a i r s w i t h enough c o n s i s t e n c y t o c o n v i n c e one t h a t t h e y a r e p a r t of t h e same w a t e r " l e n s e s " o r l a y e r s . F e a t u r e s t h i n n e r t h a n 0.1 m d e f i n i t e l y d i f f e r i n p a i r s o f p r o f i l e s . A n o t h e r way t o l o o k a t t h i s i s t o s t a t e t h a t (by v i s u a l e x a m i n a t i o n ) i f t h e s e p r o f -i l e s were low - p a s s e d f i l t e r e d w i t h a c u t - o f f a t 0.3 m, p r o f i l e s o f a p a i r would l o o k a l m o s t i d e n t i c a l . Note however t h a t c r o s s - s p e c t r a l a n a l y s i s m i ght n o t agree w i t h t h i s r e s u l t because i d e n t i f i a b l e f e a -t u r e s o f t e n have d i f f e r e n t t h i c k n e s s o r s l i g h t l y d i f f e r e n t r e l a t i v e p o s i t i o n i n the w a t e r column; t h e r e l a t i v e d i s p l a c e m e n t s c o u l d be a l i m i t i n g f a c t o r i n e s t i m a t i n g s p e c t r a l c o h e r e n c e s . Near 50 m, Drops 7, 8 and 9 p r e s e n t t e m p e r a t u r e s t e p s where s i m i l a r i t y seems t o s t o p a t s c a l e s s m a l l e r t h a n 0.5 m. I n t h e Deep Water o f t h e I n n e r B a s i n , few m i c r o s t r u c t u r e f e a t u r e s a r e a v a i l a b l e f o r m a t c h i n g . F i g . 55 t o 57 show t h a t s c a l e s s m a l l e r t h a n 1 t o 3 m a r e u s u a l l y d i f f e r e n t i n two p r o f i l e s o f a p a i r . Throughout t h e Outer B a s i n ' s Drop 6, s i m i l a r i t y between t h e p r o f i l e s i s s m a l l a t s c a l e s s m a l l e r t h a n 1 o r 2 m i n most c a s e s ( f i g . 41 t o 4 3 ) . - G i v e n a t e m p e r a t u r e change w h i c h i s sampled by two n e i g h -b o u r i n g p r o b e s , i s the same tijpz. of m i c r o s t r u c t u r e o b s e r v e d by both? Throughout t h e Howe Sound o b s e r v a t i o n s , when one t e m p e r a t u r e p r o f i l e was s t e p p y , the o t h e r one u s u a l l y was a l s o . When one p r o f i l e p r e s e n t e d h i g h a m p l i t u d e g r a d i e n t s p i k e s , so d i d the o t h e r one. T h i s a p p l i e s a l s o f o r t e m p e r a t u r e "ramps". However, when a p a t c h o f " s y m m e t r i c a l g r a d i e n t f l u c t u a t i o n s " w i t h g r a d i e n t v a r i a n c e concen-t r a t e d a t s c a l e s s m a l l e r t h a n 0.05 m was found i n one p r o f i l e , t h e o t h e r p r o f i l e seldom p r e s e n t e d a p a t c h w i t h s i m i l a r e x t e n t . Many examples o f t h i s were f o u n d i n Drop 6 ( f i g . 41 t o 4 3 ) . I n Drop 8 ( f i g . 5 7 ) , a 10 m t h i c k p a t c h o f g r a d i e n t v a r i a n c e i s found by b o t h p r o b e s b u t t h e g r a d i e n t v a r i a n c e i s d i s t r i b u t e d d i f f e r e n t l y w i t h i n each p r o f i l e . These o b s e r v a t i o n s i n d i c a t e t h a t p a t c h e s o f t e m p e r a t u r e m i c r o s t r u c t u r e o f t h e " s y m m e t r i c a l " , s m a l l s c a l e t y p e do n o t e x t e n d l a t e r a l l y o v e r d i s t a n c e s as l a r g e as 20 m i n t h e Ou t e r B a s i n (and s e l -dom o c c u r i n the I n n e r B a s i n i n F e b r u a r y 1974). O t h e r i d e n t i f i e d t y p e s o f m i c r o s t r u c t u r e appear t o e x t e n d l a t e r a l l y o v e r d i s t a n c e s l a r g e r t h a n t h e 20 or so metre s w h i c h s e p a r a t e d the f r e e - f a l l i n g p r o b e s . V.3.d) T u r b u l e n t o r no t ? There a r e p a t c h e s o f t e m p e r a t u r e m i c r o s t r u c t u r e w h i c h , i n t u i -t i v e l y , have seemed t o be " t u r b u l e n t " t o p e o p l e who have s t u d i e d t h e d e t a i l e d p r o f i l e s . The one metre t h i c k p a t c h f ound i n Drop 6 ( f i g . 41) a t 58 m i s one example o f t h i s . There a r e a l s o o t h e r r e g i o n s o f t h e w a t e r column w h i c h , i n t u i t i v e l y s t i l l , seem n o t t o be t u r b u l e n t . The l o w e r s i d e o f a t e m p e r a t u r e maximum found i n Drop 9 ( f i g . 52) i s one such example. Y e t , between extreme c a s e s l i e s t he m a j o r i t y o f m i c r o -s t r u c t u r e f e a t u r e s . I s such an assessment v a l i d o r s h o u l d " i n t u i t i o n " be c o n s i d e r e d m i s l e a d i n g ? Can t e m p e r a t u r e m i c r o s t r u c t u r e a l o n e a l l o w one t o a s s e s s t h e t u r b u l e n t o r n o n - t u r b u l e n t n a t u r e o f a f l o w ? F o r t h e purpose o f t h i s d i s c u s s i o n , the meaning of t u r b u l e n c e i s r e s t r i c t e d t o random, s m a l l s c a l e , q u a s i - i s o t r o p i c v e l o c i t y f l u c t u -a t i o n s . When t h i s o c c u r s , v e r t i c a l exchanges o f f l u i d must t a k e p l a c e and the l o c a l d e n s i t y s t r a t i f i c a t i o n must be " t u r n e d o v e r " a t s m a l l s c a l e s a t l e a s t . One t h e n e x p e c t s an i n s t a n t a n e o u s p r o f i l e o f temper-a t u r e t o p r e s e n t a d i s o r d e r e d a s p e c t a t s m a l l s c a l e s and an i n s t a n t a n -eous p r o f i l e o f t h e v e r t i c a l g r a d i e n t s h o u l d p r e s e n t f l u c t u a t i o n s w h i c h show l i t t l e p r e f e r e n c e f o r one s i g n o r t h e o t h e r . T h u s , m i c r o -s t r u c t u r e d e s c r i b e d e a r l i e r as " i r r e g u l a r g r a d i e n t " and s m a l l s c a l e " s y m m e t r i c a l " g r a d i e n t f l u c t u a t i o n s a r e t h e most c o n s i s t e n t w i t h t u r b u l e n t s t i r r i n g . I r r e g u l a r t e m p e r a t u r e p r o f i l e s and " s y m m e t r i c a l " s m a l l s c a l e g r a d i e n t f l u c t u a t i o n s do n o t n e c e s s a r i l y mean t h a t t h e f l u i d w h i c h i s b e i n g sampled i s i n t u r b u l e n t m o t i o n . One can t h i n k o f c o u n t e r examples. Take t h e case o f a b r i e f t u r b u l e n t e p i s o d e i n v o l -v i n g w a t e r s t r a t i f i e d i n d e n s i t y and t e m p e r a t u r e . Once t h r e e -d i m e n s i o n a l t u r b u l e n c e s u b s i d e s , t h e p a r t i a l l y m ixed volume of w a t e r r e o r g a n i z e s i t s e l f a c c o r d i n g t o i t s new d e n s i t y s t r u c t u r e . Because h e a t and s a l t have d i f f u s e d a t d i f f e r e n t m o l e c u l a r r a t e s , t h e r e s u l t -i n g s t a b l e w a t e r column w i l l p r e s e n t an " i r r e g u l a r " t e m p e r a t u r e p r o f i l e w i t h s m a l l s c a l e t e m p e r a t u r e i n v e r s i o n s and g r a d i e n t f l u c t u a -t i o n s o f b o t h s i g n s . Y e t , i t i s no more t u r b u l e n t i n the s e m i -i s o t r o p i c s e n s e . M o l e c u l a r h e a t d i f f u s i o n a c t s towards d i s s i p a t i n g s m a l l s c a l e t e m p e r a t u r e g r a d i e n t v a r i a n c e . . The p r e s e n c e o f h i g h wave number g r a d i e n t v a r i a n c e i n m i c r o s t r u c t u r e i s t h u s t a k e n t o s u g g e s t t h a t r e c e n t " a c t i v i t y " has t a k e n p l a c e o r i s g o i n g on. E c k a r t (1948) has shown t h a t t e m p e r a t u r e g r a d i e n t v a r i a n c e r e s u l t s from t h e d e f o r m a t i o n o f t h e t e m p e r a t u r e f i e l d by t h e r a t e o f s t r a i n o f t h e f l u i d ' s m o t i o n . Due t o t h e r m a l d i f f u s i v i t y , an i n f i n i t e l y s h a r p t e m p e r a t u r e s t e p would t a k e 180 sec t o t h i c k e n t o 0.01 m i n w a t e r (Osborn and Cox, 1972). D i m e n s i o n a l c o n s i d e r a t i o n s i n v o l v i n g a c o n s t a n t r a t e o f s t r a i n and t h e t h e r m a l d i f f u s i v i t y o f w a t e r i n d i c a t e t h a t , i n an inhomogene-ous t e m p e r a t u r e f i e l d , t e m p e r a t u r e g r a d i e n t v a r i a n c e a t s c a l e s o f t h e o r d e r o f 0.01 m can be s u s t a i n e d by a r a t e o f s t r a i n o f (180 sec) ^ o r 0.005 (m sec "S m Thus, c o m p a r a t i v e l y weak s h e a r s a r e s u f f i c i e n t t o cause g r a d i e n t v a r i a n c e a t s c a l e s s m a l l e r t h a n t h o s e r e s o l v e d by t h e i n s t r u m e n t s , w i t h o u t r e c o u r s e t o t u r b u l e n t p r o c e s s e s . Osborn ( p e r s o n a l communication) has made o b s e r v a t i o n s o f b o t h t e m p e r a t u r e and v e l o c i t y m i c r o s t r u c t u r e . He has found t h a t p a t c h e s o f b o t h u s u a l l y o c c u r t o g e t h e r . I n s e v e r a l i n s t a n c e s , he has o b s e r v e d m i c r o s t r u c t u r e s h e a r v a r i a n c e where no o r l i t t l e t e m p e r a t u r e g r a d i e n t v a r i a n c e was f o u n d . T h i s o c c u r s where t e m p e r a t u r e i s homo-geneous and b r i n g s up one more p o i n t : p a t c h e s o f v e l o c i t y m i c r o -s t r u c t u r e (and e v e n t u a l l y t u r b u l e n t m o t i o n ) may go u n d e t e c t e d by t e m p e r a t u r e s e n s o r s when the t e m p e r a t u r e d i s t r i b u t i o n i s homogeneous. On the b a s i s of t h e p r e c e d i n g d i s c u s s i o n , a t t e m p t i n g t o a s s e s s t h e o c c u r r e n c e of t u r b u l e n c e w i t h t e m p e r a t u r e s e n s o r s i s r i s k y , a t b e s t . T u r b u l e n c e may go u n n o t i c e d o r e l s e m i c r o s t r u c t u r e p a t c h e s may be n o n - t u r b u l e n t ( i n t h e s e m i - i s o t r o p i c s e n s e ) . F e a t u r e s w h i c h a r e most c o n s i s t e n t w i t h t u r b u l e n c e a r e t h o s e w h i c h p r e s e n t " s y m m e t r i c a l " g r a d i e n t f l u c t u a t i o n s a t s m a l l s c a l e s w i t h a t e m p e r a t u r e p r o f i l e s u g g e s t i n g a l o c a l d e n s i t y o v e r t u r n . Such f e a t u r e s a r e f o u n d , f o r i n s t a n c e , i n f i g . 41 t o 43 and 57. They a r e c a l l e d h e r e " t u r b u l e n t - l i k e " . On t h e b a s i s of t h e p r e c e d i n g d i s c u s s i o n , t h e r e a r e a l s o f e a t u r e s w h i c h a r e c l e a r l y n o n - t u r b u l e n t . T h i s i s t h e c a s e of r e g i o n s of the w a t e r column w h i c h p r e s e n t a monotonous t e m p e r a t u r e p r o f i l e such as f i g . 52 (Drop 8 n e a r 60 m). I n t e m p e r a t u r e "ramps" such as t h o s e found i n f i g . 24 and f i g . 41 ( n e a r 59 m), t h e r e a r e v e r y s m a l l i n v e r s i o n s i n t h e mean t r e n d . ' I n v i e w o f t h e r e g u l a r s t r u c t u r e p r e -s e n t e d by t h e p r o f i l e s , t u r b u l e n t s t i r r i n g seems t o be an u n l i k e l y e x p l a n a t i o n ' ( a t l e a s t a t the t i m e when t h a t f e a t u r e was s a m p l e d ) . I n Drop 6 ( O u t e r B a s i n , 1 9 7 4 ) , most o f t h e g r a d i e n t v a r i a n c e i s a s s o c i a t e d w i t h a t u r b u l e n t - l i k e m i c r o s t r u c t u r e . The p a t c h e s have t h i c k n e s s e s o f one h a l f t o two m e t r e s and, as shown i n the p r e c e d i n g s u b - s e c t i o n , t h e y seem t o e x t e n d l a t e r a l l y f o r l e s s t h a n about 20 m. I n t h e I n t e r m e d i a t e Water of t h e I n n e r B a s i n (10 t o 100 m) most o f t h e g r a d i e n t v a r i a n c e i s a s s o c i a t e d w i t h m i c r o s t r u c t u r e f e a t u r e s w h i c h a r e n o t t u r b u l e n t - l i k e . They c o n s i s t of t e m p e r a t u r e s t e p s accom-p a n i e d by c l u s t e r s of "one s i d e d " g r a d i e n t m i c r o s t r u c t u r e and t h e s e v a r i a n c e p a t c h e s seem t o e x t e n d l a t e r a l l y f o r more t h a n about 20 m. I n t h e Deep Water of t h e I n n e r B a s i n , some f e a t u r e s a r e t u r b u l e n t -l i k e and o t h e r s a r e n o t b u t due t o t h e p a u c i t y of d a t a from t h i s r e g i o n , no c o n c l u s i o n can be drawn. I n t h e November 1973 p r o f i l e s (see f i g . 21 t o 2 4 ) , o c c u r r e n c e s of a l l t y p e s a r e f o u n d . The numer-ous t e m p e r a t u r e i n v e r s i o n s w h i c h a r e f ound o c c u r a t s c a l e s of i m o r l a r g e r and seem t o r e s u l t more from a d v e c t i v e p r o c e s s e s such as " i n t e r l e a v i n g " r a t h e r t h a n f r o m t u r b u l e n t o v e r t u r n . V.3.e) D o u b l y - d i f f u s i v e o r n o t ? D o u b l y - d i f f u s i v e c o n v e c t i o n has f a s c i n a t e d o c e a n o g r a p h e r s e v e r s i n c e the i d e a of i t was o u t l i n e d and t r i e d i n l a b o r a t o r y t a n k s . When the 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 p r o v i d e o p p o s i t e c o n t r i -b u t i o n s t o t h e d e n s i t y g r a d i e n t of a s t a b l e w a t e r column, t h e r e i s a p o s s i b i l i t y t h a t l o c a l d e n s i t y i n s t a b i l i t i e s d e v e l o p and grow because of t h e l a r g e d i f f e r e n c e between t h e m o l e c u l a r d i f f u s i o n r a t e s o f h e a t and s a l t . The r e a d e r i s r e f e r r e d t o T u r n e r (1973) f o r a d e t a i l e d d i s -c u s s i o n o f work c a r r i e d on t h i s t o p i c b e f o r e 1973 and t o Monin e t a l . (1974) f o r an o v e r v i e w o f work c a r r i e d on b e f o r e 1972. P r e s u m p t i o n o f d o u b l y - d i f f u s i v e c o n v e c t i o n i n t h e ocean i s u s u a l l y based on v e r t i c a l p r o f i l e s o f t e m p e r a t u r e and s a l i n i t y w h i c h p r e s e n t r e g u l a r l y spaced l a y e r s o f homogeneous p r o p e r t i e s s e p a r a t e d by sharp p r o p e r t y changes o f t e n c a l l e d i n t e r f a c e s , i n w a t e r columns where, t o b e g i n w i t h , the p r o p e r t y g r a d i e n t s p r e s e n t v a l u e s c o n s i s t e n t w i t h d o u b l y - d i f f u s i v e c o n v e c t i o n . I n the d a t a p r e s e n t e d h e r e , o n l y the t e m p e r a t u r e g r a d i e n t i s known w i t h some p r e c i s i o n . Over most of t h e w a t e r column, t e m p e r a t u r e i n c r e a s e s w i t h d e p t h . S i n c e t h e w a t e r column i s s t a b l e , s a l i n i t y must i n c r e a s e w i t h d e p t h a t l e a s t i n a compensating f a s h i o n . The o v e r a l l p r o p e r t y g r a d i e n t s a r e t h e n c o n s i s t e n t w i t h t h e development of a d o u b l y - d i f f u s i v e i n s t a b i l i t y o f t h e " d i f f u s i v e t y p e " ( s e e T u r n e r , 1973). However, t h e l a r g e and r e g u l a r s t e p s w h i c h have been o b s e r v e d e l s e w h e r e a r e n o t found i n t h e Howe Sound p r o f i l e s . What i s f o u n d i s t h a t d i f f e -r e n t t y p e s o f t e m p e r a t u r e m i c r o s t r u c t u r e t e n d t o be a s s o c i a t e d w i t h p o s i t i v e and n e g a t i v e v e r t i c a l t e m p e r a t u r e g r a d i e n t s . M o r e o v e r , t h e g r a d i e n t v a r i a n c e a s s o c i a t e d w i t h n e g a t i v e t e m p e r a t u r e g r a d i e n t s i s l a r g e r t h a n t h a t a s s o c i a t e d w i t h p o s i t i v e t e m p e r a t u r e g r a d i e n t s . G a r g e t t (1976) a l s o o b s e r v e d t h i s r e l a t i o n s h i p between the i n t e n s i t y o f g r a d i e n t v a r i a n c e and t h e f i n e s t r u c t u r e g r a d i e n t w h i l e Gregg and Cox (1972) a l s o o b s e r v e d t h e s t e p p y c h a r a c t e r o f m i c r o s t r u c t u r e when t e m p e r a t u r e l o c a l l y i n c r e a s e s downwards. These a u t h o r s a g r e e t h a t d o u b l y - d i f f u s i v e c o n v e c t i o n i s v e r y l i k e l y t o p l a y a r o l e i n s h a p i n g m i c r o s t r u c t u r e . Gregg and Cox (1972) d i s c u s s t h i s i n more d e t a i l and show t h a t S o r e t d i f f u s i o n c o u l d a l s o be r e l e v a n t . However, on t h e b a s i s o f t h e i r d a t a and on t h e s t a t e o f knowledge, t h e s e a u t h o r s c o u l d n o t come t o a c o n c l u s i o n about t h e i m p o r t a n c e o f d o u b l y -d i f f u s i v e p r o c e s s e s i n o c e a n i c e n v i r o n m e n t s . The same a p p l i e s h e r e . C h a p t e r V I C o n c l u s i o n Howe Sound's w a t e r i s shown t o p r e s e n t t h r e e w a t e r masses. The S u r f a c e L a y e r o c c u p i e s t h e upper 10 m and e v o l v e s under t h e i n f l u e n c e o f f r e s h w a t e r r u n o f f , t i d e s and m e t e o r o l o g i c a l e f f e c t s . The I n t e r m e d i a t e Water i s c h a r a c t e r i z e d by i t s exchanges w i t h t h e S t r a i t o f G e o r g i a . F l u s h i n g t i m e can be as s h o r t as a few weeks. The I n t e r m e d i a t e Water i s c o n s i d e r e d t o occupy t h e whole o f t h e Ou t e r B a s i n (below 10 m) and the d e p t h range o f 10 t o 100 m i n t h e I n n e r B a s i n . The Deep Water o c c u p i e s t h e I n n e r B a s i n o n l y , below 100 m. I t s t a y s t r a p p e d f o r p e r i o d s o f months t o y e a r s . Two t e m p e r a t u r e m i c r o s t r u c t u r e c r u i s e s w h i c h were made i n Howe Sound r e v e a l e d t y p e s o f m i c r o s t r u c t u r e w h i c h v a r i e d w i t h l o c a t i o n , d e pth and t e m p e r a t u r e f i n e s t r u c t u r e . I n t h e Ou t e r B a s i n , most of the v e r t i c a l t e m p e r a t u r e g r a d i e n t v a r i a n c e 9^ o c c u r s i n a s s o c i a t i o n w i t h t u r b u l e n t - l i k e m i c r o s t r u c t u r e p a t c h e s 0.5 t o 3 m t h i c k w h i c h seem t o e x t e n d l a t e r a l l y f o r l e s s t h a n 20 m. I n t h e I n n e r B a s i n , most of the g r a d i e n t v a r i a n c e i s a s s o c i a t e d w i t h m i c r o s t r u c t u r e f e a t u r e s w h i c h appear t o be n o n - t u r b u l e n t a t t h e ti m e o f s a m p l i n g . I n t h e I n n e r B a s i n ' s I n t e r m e d i a t e Water, t h e l a t e r a l e x t e n t o f t h e g r a d i e n t v a r i a n c e p a t c h e s as w e l l as t h a t o f i n d i v i d u a l f e a t u r e s as t h i n as 0.2 m, seems t o be l a r g e r t h a n 20 m l a t e r a l l y . I n t h e Deep Water, few m i c r o s t r u c t u r e f e a t u r e s a r e d e t e c t e d . When t h e y a r e , o n l y s c a l e s l a r g e r t h a n 1 o r 2 m seem t o e x t e n d f o r more t h a n about 20 m l a t e r a l l y . R e g i o n s o f the w a t e r column where t h e t e m p e r a t u r e g r a d i e n t ( a t s c a l e s o f 0.5 t o 2m) i s p o s i t i v e ( t e m p e r a t u r e d e c r e a s i n g downwards) p r e s e n t l e s s g r a d i e n t v a r i a n c e and smoother t e m p e r a t u r e p r o f i l e s . R e g i o n s where t h e t e m p e r a t u r e g r a d i e n t i s n e g a t i v e o f t e n p r e s e n t s t e p p y t e m p e r a t u r e p r o f i l e s and t h e g r a d i e n t peaks a t c o m p a r a t i v e l y h i g h v a l u e s . These comments a p p l y t o m i c r o s t r u c t u r e w h i c h was n o t t u r b u l e n t - l i k e . I n the November 1973 d a t a , m i c r o s t r u c t u r e p a t c h e s w h i c h c o u l d be d e s c r i b e d as t u r b u l e n t - l i k e o c c u r e q u a l l y w e l l w i t h i n r e g i o n s o f mean g r a d i e n t o f b o t h s i g n s . The r o l e o f t e m p e r a t u r e m i c r o s t r u c t u r e i s examined i n t h e l i g h t o f t h e Osborn-Cox model and of a n o t h e r model f o r m i x i n g w h i c h i s d e v e l o p e d i n t h i s t h e s i s . The Oxborn-Cox model i s a p p l i e d t o t h e l o w e r p a r t o f t h e I n n e r B a s i n ' s I n t e r m e d i a t e Water. I t s u g g e s t s t h a t v e r t i c a l t u r b u l e n t d i f f u s i o n p l a y s o n l y a m i n o r r o l e i n t h e I n t e r m e d i a t e Water near 75 m, compared t o l a t e r a l a d v e c t i v e exchanges between t h e I n n e r B a s i n and t h e o u t s i d e . The m i x i n g model d e v e l o p e d h e r e r e t a i n s as i m p o r t a n t p a r a m e t e r s the t e m p e r a t u r e v a r i a n c e w i t h i n t h e Deep Water, th e mean s q u a r e t e m p e r a t u r e g r a d i e n t , m o l e c u l a r h e a t d i f f u s i o n and a ti m e s c a l e f o r t h e m i x i n g o f t h e Deep Water. B o t t l e c a s t d a t a s u g g e s t a t h r e e month ti m e s c a l e f o r m i x i n g t h e Deep Water. Deep Water g r a d i e n t v a r i a n c e d a t a a r e s c a n t b u t th e y a r e of an o r d e r o f magnitude w h i c h i s c o m p a t i b l e w i t h t h a t p r e d i c t e d by t h e model f o r t h e t h r e e month t i m e s c a l e . The r e s u l t s s u g g e s t e d by t h e models a r e l i m i t e d by t h e a b i l i t y o f t h e pr o b e s t o r e s o l v e t h e f u l l s p e c t r u m o f t e m p e r a t u r e g r a d i e n t v a r i -ance and by t h e p o s s i b l e i n t e r m i t t e n c y o f m i c r o s t r u c t u r e p r o d u c i n g e v e n t s . R e f e r e n c e s BELL, W i l l i a m H. 1973. The Exchange o f Deep Water i n Howe Sound B a s i n . P a c i f i c M a r i n e S c i e n c e D i r e c t o r a t e R e p o r t 73-13, E n v i r o n m e n t Canada, V i c t o r i a , B.C. BELL, W i l l i a m H. 1975. The Howe Sound C u r r e n t M e t e r i n g Program, Volume I I I , P a r t I - D a t a R e p o r t , S t a t i o n HS-5. P a c i f i c M a r i n e S c i e n c e R e p o r t 75-7. I n s t i t u t e o f Ocean S c i e n c e , P a t r i c i a Bay, V i c t o r i a , B.C. BUCKLEY, J o s e p h R. 1977. C u r r e n t s , w i n d s and t i d e s i n Howe Sound. Ph.D. T h e s i s , 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 , V a n c o u v e r , B.C. pp. 228. Can a d i a n H y d r o g r a p h i c S e r v i c e . 1977. Ca n a d i a n T i d e and C u r r e n t T a b l e s , V o l . 5, J u a n de Fuca and S t r a i t o f G e o r g i a . C a n a d i a n H y d r o g r a p h i c S e r v i c e , M a r i n e S c i e n c e B r a n c h , Department o f t h e E n v i r o n m e n t , Ottawa, Canada. DAHL, F i n n - E . 1977. A Note on H o r i z o n t a l G r a d i e n t s i n F j o r d s . J o u r . P h y s . Oceanog. 7_(5): 753-758. DEFANT, A l b e r t . 1961. P h y s i c a l Oceanography, V o l . I I . Pergamon P r e s s . DRINKWATER, Kenneth F. 1973. The R o l e o f T i d a l M i x i n g i n R u p e r t and H o l b e r g I n l e t s . M. Sc. T h e s i s , 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 , V a n c o u v e r , B.C. pp. 58. ECKART, C a r l . 1948. An A n a l y s i s o f t h e S t i r r i n g and M i x i n g P r o c e s s e s i n I n c o m p r e s s i b l e F l u i d s . J o u r . Mar. Res. VI I , 3 : 2 6 5 - 2 7 5 . ELLIOTT, J.A. and N.S. OAKEY. 1975. H o r i z o n t a l c o h e r e n c e o f Temperature M i c r o s t r u c t u r e . J o u r . P h y s . Oceanog. 5_: 506-515. GARGETT, Ann. 1976. An I n v e s t i g a t i o n o f t h e O c c u r r e n c e o f O c e a n i c T u r b u l e n c e w i t h r e s p e c t t o F i n e s t r u c t u r e . J o u r . Phys. Oceanog. 6:139-156. GREGG, M.C. and C.S. COX.,1972. The V e r t i c a l M i c r o s t r u c t u r e o f Temperature and S a l i n i t y . Deep Sea Res. 19:355-376. GREGG, M.C, C.S. COX and P.W. HACKER. 1973. V e r t i c a l M i c r o s t r u c t u r e Measurements i n t h e C e n t r a l N o r t h P a c i f i c . J o u r . Phys. Oceanog.' _3:458-469. I n s t i t u t e o f Oceanography o f t h e 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 . 1973. Da t a R e p o r t 34. B r i t i s h C o l u m b i a I n l e t s and P a c i f i c C r u i s e s 1972. 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 , V a n c o u v e r , B.C. I n s t i t u t e o f Oceanography of t h e 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 . 1974. Data R e p o r t 35. B r i t i s h C o l u m b i a I n l e t C r u i s e s 1973. 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 , V a n c o u v e r , B.C. I n s t i t u t e o f Oceanography of 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 . 1975. Da t a R e p o r t 37. B r i t i s h C o l u m b i a I n l e t C r u i s e s 1974. 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 , V a n c o u v e r , B.C. LUECK, R o l f G., Owen HERTZMAN and Thomas R. OSBORN. 1977. The S p e c t r a l Response o f T h e r m i s t o r s . Deep Sea Res. 24:951-970. MONIN, A.S. 1977. V a r i a b i l i t y o f the Oceans. John W i l e y and Sons. OSBORN, T.R. and C.S. COX. 1972. O c e a n i c F i n e S t r u c t u r e . Geophys. F l u i d Dyn. _3:321-345. OSBORN, T.R. 1977. The D e s i g n and P e r f o r m a n c e o f F r e e F a l l M i c r o s t r u c t u r e I n s t r u m e n t s a t the I n s t i t u t e o f Oceanography. U n p u b l i s h e d m a n u s c r i p t , I n s t i t u t e o f Oceanography, 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 , Vancouver, B.C. PICKARD, G.L. 1975. A n n u a l and Lo n g e r Term V a r i a t i o n s o f Deep Water P r o p -e r t i e s i n C o a s t a l Waters o f S o u t h e r n B r i t i s h C o l u m b i a . J o u r . F i s h . Res. B o a r d Canada 32:1561-1587. STOMMEL, H. and K.N. FEDOROV. 1967. S m a l l S c a l e S t r u c t u r e i n Temperature and S a l i n i t y n e a r Timor and Mindanao. T e l l u s 19(2):306-325. TURNER, J.S. 1973. Buoyancy E f f e c t s i n F l u i d s . Cambridge U n i v e r s i t y P r e s s , 367 pp. 75 Drop L o c a t i o n Date Hour S e p a r a t i o n S e p a r a t i o n Number a t l a u n c h a t r e c o v e r y ( 1 9 7 4 ) ±10% ±50% 3 R a m i l l i e s Channel 5 Feb. 09:25 15 m 10 m 4 " " " 11:00 7 m N/A 5 " " " 13:40 3 m 20 m 6 " " " 14:10 20 m N/A 7 S t a t i o n Howe 4 6 Feb. 09:10 20 m 25 m 8 " " " 10:10 3 m 12 m 9 " " " 11:15 10 m N/A 10 S t a t i o n Howe 4.7 " 12:55 20 m 1 m 11 " " " 14:00 3 m N/A T a b l e I L i s t o f t h e d o u b l e drops made i n t h e F e b r u a r y 1974 c r u i s e i n Howe Sound's b a s i n s , t o g e t h e r w i t h t h e s e p a r a t i o n o f t h e pr o b e s a t l a u n c h and a t r e c o v e r y . 76 Drop Number Date (1973) Time L o c a t i o n Mean Square G r a d i e n t 10 3 ( C ° / m ) 2 Depth I n t e r v a l (m) P-10 P - l l P-12 P-13 P-14 P-15 P-16 21 Nov. 22 Nov. 10:25 11:20 12:30 13:30 14:10 15:20 08:43 Howe 4 Howe 3.8 Howe 4 Howe 4 Howe 4 Howe 4 Howe 4.7 11.0 18.0 46.9 18.2 22.8 39.2 17.2 38 183 27 210 28 152 27 187 19 202 28 70 28 183 T a b l e I I Times and l o c a t i o n s a t w h i c h Drops P-10 t o P-16 were made d u r i n g t h e November 1973 c r u i s e i n Howe Sound. The v a l u e s o f t h e mean s q u a r e g r a d i e n t s and t h e d e p t h i n t e r v a l s o v e r w h i c h t h e y were o b s e r v e d a r e a l s o g i v e n . The mean t e m p e r a t u r e g r a d i e n t s o v e r t h e s e i n t e r v a l s was n o t c a l c u l a t e d because t h e p r o f i l e s p r e s e n t numerous major t e m p e r a t u r e i n v e r s i o n s . 77 Drop Number I n t e r m e d i a t e Water T h i c k n e s s (m) Temperature Mean Square Change G r a d i e n t (C°) (C°/m) 2 x 10 3 6-A 6- B 7- A 7- B 8- A 8- B 9- A 9-B 10-A 10-B 152 162 80 79 89 85 82 83 83 85 2.0 1.8 1.1 1.3 1.5 1.4 1.4 1.5 1.5 1.4 35. 18. 6.2 9.8 7.1 11.4 8.3 9.0 9.0 8.1 T a b l e I I I Temperature change and g r a d i e n t v a r i a n c e f o u n d i n t h e I n t e r m e d i a t e Water i n F e b r u a r y 1974. 78 79 Figure 2 Longitudinal section of Howe Sound and cross channel sections made at the s i l l ( ) and at Howe 4 ( ). 0 1 0 0 k 2 0 0 T(°C) 7 9 S ( % o ) 2 9 31 O u t e r E a s i n T ( °C) 7 9 S ( % o ) 2 9 31 I n n e r B a s i n Figure 3 Typical winter profiles of temperature and salinity in the Outer Basin and in the Inner Basin (February 1974) CO o 81 T e m p e r a t u r e ( °C) O O) oo n o o 82 O u t e r B a s i n H o w e 2 8*3 U cL E 6 _ 3 0 . 4 o °: 3o.o >* c 29.6 oo 29.4 S A L I N I T Y 1 0 8 6 3 0 . 4 4- 30 .0 4 29 .6 29 .4 1 9 7 2 1 9 7 3 74 I n n e r B a s i n H o w e 4 . 5 30.4 + oo 29.4 J ( J A , S O . N D . J . F M A M . J . J A , S O . N . D . J j ^ 3 0 . 0 10 8 6 1 9 7 2 1973 Figure 5 Comparison between the temperature and s a l i n i t y average values in the Intermediate Water of the Inner and Outer Basin. u o a E 0) a) 2 0 0 m / \ 2 0 0 m 1 0 0 m - t - H — — I — I — I — 1 — I — t N D ' J F 1972 i i I I I N D ' J F 1 0 0 m T E M P E R A T U R E ' ' ' ' • i i i i i i I I I i i i 1 9 7 3 N D ' J F 1974 t 9 + 8 Key t o Symbols: a 250 m A 2 2 5 m __200m o 175 m O 150m • 125 m — 100m 3 0 . 0 6 f 30 .021 b) 30 .04 + N ~ , "\ o o o o o A -S-• • • / 2 0 0 m o l O O m o / \ V S A L I N I T Y H—H N D ' J F H — h - H — I — I — I — I — I — I — I -+ 3 0 . 0 6 4-30.04 4- 30 .02 1 9 7 2 N D ' J F - J — I — I — i — i — i — i — i — t -1 9 7 3 N D ' J F - I — i — i — I — i -1974 F i g u r e 6 a) and b) 84 O O O CD lO CM CM 1- euu6!S O CM —h-CM — e o o < ©C5<i0 E •090 o e <3aQ O <J8i CM 1 > CD |<D /•O o VCJ /•OO / OQ T3 > o Q c O) >} 01 -4- -4-( |/|UJ)-0'Q CD a z 0> Q Z CM u. -> Q Z CM t -T3 C 0) 3 60 •H fe SURFACE LAYER 1 | F i gure 7 L o n g i t u d i n a l s e c t i o n of Howe Sound showing what i s meant by Deep Water and Intermediate Water. CO F i g u r e 8 87 F i g u r e 9 F i g u r e 10 H* 00 C >-f ft) o E J", NOVEMBER 25 26 27 28 29 30 31 1 2 3 A 5 6 7 8 9 10 11 12 13 14 15 8 J • I0i 0 M -10J 2 0 re ft N 10 0 10_J 600 300-I 0 V iV -i r~ 11?, J2f."i29.^c§.iy_r?_§i1 J^-Q M J ° c ) U 1 .if 1^ N-S Current at 150M (cm/sec) Prediction of Tidal Excursions (M) wr 'i [-9 0 O •8 r»10 n 3 • 0 Ul -10 n Wind Record at Squamish (M/sec) Squamish River Discharge (M7sec) V o N •10 3 o « I L10 s 600 -300 £ n 0 CO ^3 COATING F i g u r e 12 91 DROP P-16 (HOWE 4.7, EAST SIDE) DROP P-]0 DROP P-12 DROP P-13 DROP P-14 DROP P-15 (HOWE 4) DROP P - l l (HOWE 3.8) .SILL Fi gure 1 3 Location of the temperature m i c r o s t r u c t u r e p r o f i l e s made during the November 1973 c r u i s e i n Howe Sound. F i g u r e 14 O v e r a l l p r o f i l e o f Drop P-10 F i g u r e ,15 O v e r a l l p r o f i l e o f Drop P - l l 94 F i g u r e 16 O v e r a l l p r o f i l e o f Drop P-12 F i g u r e 17 O v e r a l l p r o f i l e o f Drop P-13 F i g u r e 18 O v e r a l l p r o f i l e o f Drop P-14 F i g u r e 20 O v e r a l l p r o f i l e o f Drop P-16 i r 8.4 8.6 TEMPERATUFE (°C) i r + + + + + + + + + + I L 8,8 2.0 0.0 •2.( Gradient (C /m) F i g u r e 21 D e t a i l e d p r o f i l e from drop P-12, F i g u r e 22 D e t a i l e d p r o f i l e f rom drop P-12. F i g u r e 23 D e t a i l e d p r o f i l e from drop P-13, 102 W 1 1 1 TEMPERATURE ( C) 1 • 0 - 1 - 2 GRADIENT (C°/m) F i g u r e 24 D e t a i l e d p r o f i l e from drop P-13. 103 Figure 25 STD l o n g c h a n n e l s e c t i o n made on November 13,1973 i n Howe Sound's b o t h b a s i n s . 104 STD c r o s s c h a n n e l at s t a t i o n Howe 4 F i g u r e 26 s e c t i o n made on November 22,1973 ( I n n e r B a s i n ) . Q O O O O CM o o /—\ m o o tu •> oo i 5 o 00 v—' I 2 s o O F i g u r e 27 STD c r o s s c h a n n e l s e c t i o n made on No-vember 22,1973 a t s t a t i o n Howe 4.7 ( I n n e r B a s i n ) . 106 F i g u r e 28 L o c a t i o n o f t h e t e m p e r a t u r e m i c r o s t r u c t u r e p r o f i l e s made d u r i n g t h e F e b r u a r y 1974 c r u i s e i n Howe Sound. T E M P E R A T U R E C O R M S . GRADIENT lc°/m) M E A N G R A D I E N T ( c ' / m ) 110 F i g u r e 32 O v e r a l l p r o f i l e o f Drop 9 Figure 33 Overall profile of Drop 10 112 TEMPERATURE R # M - S > VERTICAL Figure 34 Deep p a r t o f Drop 7 w i t h an expanded t e m p e r a t u r e s c a l e . 113 TEMPERATURE C ° c ) 7.5 7.7 7.9 ! 8.1 i R.M.S. VERTICAL GRADIENT (C°/m) 8.3 1.0 J ! J : I I l _ 200 F i g u r e 35 Deep p a r t o f Drop 8 w i t h an expanded t e m p e r a t u r e s c a l e . 114 Figure 36 Deep p a r t o f Drop 9 w i t h an expanded t e m p e r a t u r e s c a l e . 115 F i g u r e 37 Deep p a r t of Drop 10 w i t h an expanded t e m p e r a t u r e s c a l e . 116 Temperature ( C) 100 Depth (m) 150 J 200 250 F i g u r e 38 Comparison between t e m p e r a t u r e p r o f i l e s t a k e n two weeks b e f o r e and d u r i n g t h e F e b r u a r y 1974 m i c r o s t r u c t u r e c r u i s e . On t h e l e f t , p r o f i l e s f rom the O u t e r B a s i n : S t a t i o n Howe 3, J a n u a r y 22, 1974. R a m i l l e s C h a n n e l , F e b r u a r y 5, 1974. On t h e r i g h t , p r o f i l e s from t h e I n n e r B a s i n : S t a t i o n Howe 4.5, J a n u a r y 23, 1974. S t a t i o n Howe 4.5, F e b r u a r y 6, 1974. F i g u r e 39 STD l o n g c h a n n e l s e c t i o n made i n Howe Sound's I n n e r B a s i n on F e b r u a r y 6,1974. Figure 40 STD cross channel section made at st a t i o n Howe 4 on February 6, 1974. 119 I C '•H •a l r ~ v — — w i „ 0 0 i n o Figure 41 Detailed profile from Drop 6 Figure 42 Detailed profile from Drop 6. to o 121 F i g u r e 44 D e t a i l e d p r o f i l e from Drop 7 123 F i g u r e 45 D e t a i l e d p r o f i l e from Drop 7 F i g u r e 46 D e t a i l e d p r o f i l e from Drop 7 125 F i g u r e 47 D e t a i l e d p r o f i l e from Drop 8 126 F i g u r e 48 D e t a i l e d p r o f i l e f rom Drop 8 127 128 F i g u r e 50 D e t a i l e d p r o f i l e from Drop 9 129 F i g u r e 51 D e t a i l e d p r o f i l e f rom Drop 9 130 Figure 52 Detailed p r o f i l e from Drop 1 0 131 ^ m 4ruJ L o 132 F i g u r e 54 D e t a i l e d p r o f i l e from Drop 10 133 F i g u r e 55 D e t a i l e d p r o f i l e from the Deep Water of Drop 7 F i g u r e 56 t a i l e d p r o f i l e from the Deep Water of Drop 7 135 . i 1 --— E o u o F i g u r e 57 D e t a i l e d p r o f i l e from the Deep Water of Drop 8 

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