These two frontal zones are reflected in sea surface temperature minima 

 situated near the coast and centered at approximately S^N and 10°N (figure 16) 

 and are indications of offshore flow at these latitudes. The TIROS-N satellite 

 infrared image for 12 July 1979 (figure 22) also shows the two warm eddies and 

 the two bands of cold upwelled water being advected offshore. 



Figures 18 and 19 do not indicate the presence of a front between 3°N and 

 5°N. The broad area of low-salinity (<35.1 °/oo) water stretching along the 

 coast from S^N to about 10°N is the result of both the entrainment of compara- 

 tively fresh South Equatorial Current water into the Great Whirl and Ekman 

 transport and entrainment of coastal upwelled water. The frontal zone between 

 the Southern Eddy and Great Whirl breaks down during the rather short time of 

 approximately ten days. The tanker section taken between 220N and 2°S from 10 

 August to 17 August (figure 23) indicates a northward migration of the northern 

 edge of the Southern Eddy of approximately 100 nmi from its observed position 

 in late June and early July. An extremely well-formed Great Whirl off the 

 Somali Coast between 50N and lOON is seen in the TIROS-N satellite infrared 

 image for 18 August 1979 (figure 2). The Southern Eddy is unfortunately 

 obscured by clouds but it is undoubtedly present owing to the pronounced 

 ribbon of cold water on the southern edge of the Great Whirl. 



The XBT cross-section taken by the ESSO CARRIBEAN from 25 to 31 August 

 1979 between 20S and 22°N (figure 24) reveals a single front at 9°N separating 

 two large warm eddies centered at approximately 5°N and 12°N. The Southern 

 Eddy and Great Whirl had merged into a single warm anticyclonic eddy. In the 

 TIROS-N satellite IR image for 27 August 1979 (figure 3), the front between 

 the Southern Eddy and the Great Whirl has disappeared. The upwelled water off 

 the coast between 9°N and 10°N seen in the image is manifested in the sharp 

 peaking of isotherms in the ESSO CARRIBEAN cross-section at the same latitude. 

 This cold upwelled water forms the southwestern edge of the Socotra Eddy. 



The interplay between water masses of different origin is evident in 

 temperature-salinity relationships from the STD stations taken in the area. 

 The gross shapes of the temperature-salinity (T-S) curves (figure 25) in the 

 area show only slight variation in salinity from the surface down to 1500 m. 

 Although T-S curves in this region are encompassed by a fairly narrow salinity 

 envelope, these curves are characterized by a rather ragged and irregular 

 salinity structure in the layer between 200 m and 1000 m. Below the salinity 

 minima and maxima of the intermediate layers (300 m - 800 m) the T-S curves 

 between 800 m and 1500 m show remarkably uniform straight lines between the 

 points T=10.0OC, S=35.4 o/oo and T=5.0OC, S=34.9 o/oo in the region of the 

 Somali Basin. Some of this water (T>9°C) is from the Subtropical Convergence 

 near latitude 40OS (Warren, et^ al. , 1966). This water is too warm and too 

 saline to be considered Antarctic Intermediate Water. Antarctic Intermediate 

 Water with its strong salinity minimum (<34.65 °/oo) is obliterated by 

 southward-flowing high salinity water from the northwestern Indian Ocean 

 between 15°S and 5°S (Warren, et^ al- , 1966). 



The water which underlies the Subtropical Subsurface Water in the Somali 

 Basin is the North Indian Deep Water whose upper limit is found on the 27.6 a^ 

 surface (T=6.5°C, S=35.1 °/oo) and is located at 1200 to 1300 m depth. Below 

 1300 m, salinity decreases monotonically with temperature until abyssal values 

 of 1.30c and 1.40c are reached (Warren, et al . , 1966). The smooth continuous 



