OCEANIC CIRCULATION AND OCEAN-ATMOSPHERE INTERACTIONS 



more refined ocean models if these 

 climatic calculations are to be reliable 

 enough to be the basis for public 

 policy decisions on pollution control. 



Time-Scale of Significant Ad- 

 vances — Since published papers on 

 three-dimensional ocean circulation 

 models have only recently begun to 



appear, rapid development should 

 continue for at least another five 

 years along present lines. In that 

 time, ocean models should have 

 reached about the same level of 

 development as the most advanced 

 atmospheric numerical models today. 

 Within five years, at least the feasi- 

 bility of application of numerical 



modeling to small- and large-scale 

 pollution studies, long-range weather 

 forecasting, and hydrographic data 

 analysis should be well established. 

 Another five years will probably be 

 required to work out standard pro- 

 cedures for using numerical ocean 

 circulation models in these applica- 

 tions. 



Effects of Antarctic Water on Oceanic Circulation 



Except for a relatively thin (slightly 

 less than one kilometer) warm surface 

 layer in the tropics and subtropics, 

 the ocean is basically cold and fairly 

 high in dissolved oxygen content. 

 Ninety percent of the ocean is colder 

 than 8 centigrade, with an oxygen 

 content generally from 50 to 90 per- 

 cent of the saturation level. This 

 warm surface layer, because of its 

 high stability, acts as an impervious 

 cap over the cold abyssal water, 

 blocking renewal (by the usual tur- 

 bulent transfer methods) of the oxy- 

 gen that has been consumed by 

 various biological processes. 



warm and low-oxygen-content cir- 

 cumpolar deep water (CDW) slowly 

 flows southward and upward. Even- 

 tually, it reaches the near-surface 

 layers at the wind-produced Antarc- 

 tic Divergence. Here, the intense 

 thermohaline alteration resulting from 

 the sea-air interaction converts the 

 CDW into "antarctic surface water" 

 (AASW), which is cold (near freez- 

 ing, —1.6° to —1.9° centigrade) 

 and relatively fresh. Some of the 

 CDW is converted by more intense 

 thermohaline alterations due to ice 

 formation into a fairly dense con- 

 tinental shelf water. At certain times, 



this shelf water drops to the sea floor 

 where, on mixing with additional 

 CDW, it forms the "antarctic bottom 

 water" (AABW); neither the times 

 nor the exact locations of the vertical 

 motion are adequately known. The 

 AABW has worldwide influence. It 

 reaches far into the northern hemi- 

 sphere in the western Atlantic and 

 Pacific oceans. 



Though we do not know how the 

 shelf water is produced, three meth- 

 ods appear to be likely: (a) sea-ice 

 formation; (b) freezing, melting, or 

 a combination of these at the floating 



Why, therefore, is the bulk of the 

 ocean so cold and highly oxygenated? 

 In studying the relationship of tem- 

 perature to salinity in the cold abyssal 

 waters of the world ocean, one is 

 struck by its similarity to that found 

 in antarctic waters. This suggests 

 that the oceanographic processes oc- 

 curring in antarctic waters influence, 

 in a direct way, the physical and 

 chemical properties of much of the 

 ocean's abyssal water. One may 

 think of the antarctic region as a 

 zone in which the abyssal waters can 

 "breathe," renew their oxygen sup- 

 ply, and release to the atmosphere the 

 heat received at more northern lati- 

 tudes. 



The Antarctic Water Masses 



Figure IV-3 — ANTARCTIC WATERS AND THEIR CIRCULATION 



POLAR 

 FRONT 

 ZONE 



ANTARCTIC 

 DIVERGENCE 



ZTlUE^NTARCTirr^ \ A /?/ "^AiTARCTIC 

 IURFACI 

 WATER 



h(>' 



ICE SHELF 



S S™ E -^^7i~<i 



J /C J jV __ __ _WATER_ ,- 7 C ^J,^ -« 

 _-__ _- /" ff ", ,UPPER| / 



^ARCTIC ¥te7mE0\M£ -/ 7 $/ 



WATER / j y{i 



¥k 



I j SLOPE 



COASTAL 

 SHELF 



CIRCUMPOLAR DEEP WATER 



f~ 



MIXING 



(LOWER) 



ANTARCTIC BOTTOM WATER 



y 



The basic circulation pattern along 

 a north-south plane in antarctic wa- 

 ters is shown in Figure IV-3. The 



This figure shows the position, circulation, and interaction of the several water 

 masses found in the antarctic region. 



83 



