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t o make m o n t h - l o n g measurements at each of some 300 s t a t i o n s i n v a r i o u s par ts of the o c e a n . The l o c a t i o n o f these s t a t i ons i s be ing s t u d i e d . I n par t the measurements can be made by sh ips o f o p p o r t u n i t y , i n part by t i d a l e x p e d i t i o n s devo ted p r i m a r i l y to such measurements . I n e i t he r case the ins t rument i s p l an t ed on the sea f l o o r and r e c a l l e d to the su r f ace at a l a t e r d a t e . There i s no need fo r the s t a t i ons t o be made s i m u l t a n e o u s l y s i n c e the t i d e p roduc ing fo rce s are k n o w n . W h e r e s eve ra l i n s t rumen t s are r e - co rd ing s i m u l t a n e o u s l y , however , t ime v a r i a t i o n s i n the pressure d i f f e r e n c e s be tween s t a t ions w i l l g i v e i n f o r m a t i o n on v a r i a t i o n s i n ba ro t rop i c c u r r e n t s . I t seems l i k e l y tha t the exper ience g a i n e d i n the new t e c h n i q u e o f bo t tom pressure measurement w i l l l e ad to u s e f u l data f o r i n c l u s i o n i n a g l o b a l ocean f o r e c a s t sys t em and tha t v a r i o u s a r rays and v a r i a t i o n s o f these ins t rumen t s w i l l e v e n t u a l l y become an impor tan t part o f the g l o b a l f o r e - c a s t i n g s y s t e m , 7 . ) The Deep Ocean I t w o u l d be a m i s t a k e to l i m i t the a c t i v i t i e s o f IDOE e n t i r e l y to su r f ace l a y e r s . Human o c c u p a t i o n o f the ocean w i l l b e g i n a t the b o t t o m . Unde r s t and ing of the mechan ism and ra te o f f o r m a t i o n o f deep w a t e r s , and t h e i r t r anspor t and exchange be tween b a s i n s and be tween oceans are i m - por tan t e lements i n the o v e r a l l unde r s t and ing of how the ocean w o r k s . I n - t e r a c t i o n s of the deep ocean w i t h the su r face l a y e r can have impor t an t i m - p l i c a t i o n s fo r p r imary p r o d u c t i o n and f i s h e r i e s ; t hey a l s o r e l a t e t o the a l t e r - a t i o n o f su r face c o n d i t i o n s a f f e c t i n g the a tmosphe re . But much o f the deep ocean remains to be e x p l o r e d to e s t a b l i s h i t s average s t a t e . - 116 -
A b a s i c set o f h i g h q u a l i t y obse rva t ions o f t empera ture , s a l i n i t y , d i s s o l v e d oxygen and nu t r i en t s be tween su r face and bo t tom i s a f i r s t r e - q u i r e m e n t . O n l y s i nce 1954 has a s u i t a b l y p rec i se method fo r de t e rmin ing s a l i n i t y been a v a i l a b l e . M a n y s u i t a b l e deep s t a t i o n s have been made s ince 1954, but there are s t i l l l a rge r eg ions f r o m w h i c h no data are a v a i l a b l e . The most consp i cuous gaps are the W e d d e l l Sea, A r c t i c Ocean , southern par ts of a l l oceans , and some par ts of the Nor th I n d i a n and P a c i f i c O c e a n s . There are t w o v i e w s as to how these new s t a t i ons shou ld be d i s t r i b u t e d . The f i r s t v i e w i s the o p t i m i s t i c one: a s u i t a b l e g r i d migh t be t o have one such s t a t i o n per u n i t area of 30 x 10^ km^ (a f i ve -deg ree square near the equa to r ) . About 1,000 s t a t ions w o u l d then s u f f i c e ; at mos t , h a l f of these areas c o n t a i n modern h i g h q u a l i t y deep o b s e r v a t i o n s . I t shou ld be p o s s i b l e t o sample the res t d u r i n g the Decade , i n l a rge part f r o m c r u i s e s w i t h some other pr imary m i s s i o n . Since observers f r o m a v a r i e t y o f i n s t i t u t i o n s and coun t r i e s might be i n v o l v e d , i t i s e s s e n t i a l tha t s t anda rd ized t echn iques o f h i g h q u a l i t y and k n o w n accu racy be u s e d . S p e c i a l e f f o r t w i l l be r e q u i r e d t o make the obse rva t i ons i n h i g h l a t i t u d e s , p a r t i c u l a r l y i n w i n t e r . The reason t ha t t h i s d i s p o s i t i o n of stations i s properly c a l l e d the optimistic vlev. is that the number o f stations i s the absolute minimum. General oceanographic experience of the past indicates that isolated single stations are of limited use, and that regular dense sections across major ocean basins - such as carried out i n the Atl a n t i c during the IGY - are highly desirable. This i s the second view - the pessimistic one: namely that there i s no use s h i r k i n g the work o f making good sections across a l l major ocean basins. - 117 -
The two p r i n c i p a l regions of deep and bottom water formation appear to be the Weddell Sea and the region off southern Greenland. Winter observations i n these regions are required to understand the sinking mechanisms and to ascertain i t s variations i n time and space. Both ocean and atmosphere are involved and must be measured. I t i s d i f f i c u l t , i f not impossible, to work these regions during winter i n surface v e s s e l s , and serious consideration should be given to using a suitably equipped submersible. Completion of the desired net of deep stations would permit a quantitative inventory of volume and d i s t r i b u t i o n of a l l of the water masses of the oceans, and would provide a base l i n e for future studies of secular change i n the deep ocean. I t i s also desirable to obtain di r e c t measurements of flow of deep waters. This i s d i f f i c u l t to do on a global b a s i s , since the deep currents may be s u f f i c i e n t l y variable that prolonged measurement i s necessary. There are, however, indications that higher speeds and more steady flow occur i n the deep channels connecting ocean basins, p a r t i c u l a r l y on the western sides of oceans. Measurements of these flows are now possible, for example with unattached bottom-tethered current meters. I f such measurements were made i n the various passages connecting the several deep basins of the A t l a n t i c , Indian and P a c i f i c Oceans, and the channels through which the Antarctic Circimpolar Current flows, i t would be possible to make estimates of the balance of water, s a l t , heat and dissolved sub- stances. - 118 -
