Subtropical Subsurface Water. Immediately underlying this is another salinity 

 maximum centered between the 27.2 o^ and 27.3 a^ surfaces. This water is Red 

 Sea Water, found between the 27.2 o^ and 27.3 o^ surfaces and the 600 m and 

 800 m depths. Below 800 m, the T-S curve is nearly a straight line to 1500 m, 

 indicating the presence of North Indian Deep Water centered between 1200 m and 

 1300 m at the 27.6 at surface {S=35.1 o/oo, T=6.50C) (Warren, et al. , 1966). 

 Although North Indian Deep Water is formed in the northern part of the western 

 Indian Ocean, it is strongly diluted by Antarctic Circumpolar Water and traces 

 of Antarctic Intermediate Water. 



Station 15 (8° 27.rN, 51° 42.0'E) (figure 25) is located near the north- 

 western edge of the Great Whirl. Because this station is situated near a 

 region of strong coastal upwelling, the near surface waters down to about 

 150 m are remarkably uniform in salinity. At 200 m a salinity maximum of 

 about 35.4 °/oo appears, overlying a weak salinity minimum at about 250 m, 

 which in turn overlies a second salinity maximum at about 300 m. The two 

 salinity maxima, located on the 26.4 o^ and 26.8 a^ surfaces, are the result 

 of two tongues of Persian Gulf Water separated by an intermediate layer of 

 fresher water. The pronounced salinity minimum at 400 m is not easily ex- 

 plained from salinity analyses alone. Although Banda Sea Water and Antarctic 

 Intermediate Water could produce a salinity minimum at about 400 m, Warren et^ 

 al. (1966) feel that Subtropical Subsurface Water, which is poorer in dissolved 

 oxygen than Antarctic Intermediate Water, is responsible for the salinity 

 minimum. Unlike the salinity minima in the Atlantic and Pacific, which occur 

 together with the oxygen maxima, the salinity minimum in the Indian Ocean is 

 separate from the oxygen maximum. From this, it is reasonable to infer that 

 the intermediate salinity minimum in the Indian Ocean is not attributable to 

 Antarctic Intermediate Water. The salinity maximum between 600 m and 800 m is 

 Red Sea Water with a a^ value of about 27.3. Below Red Sea Water at about 

 800 m, the T-S curve becomes quite smooth and uniform and is a nearly straight 

 line down to 4000 m. Underlying the Red Sea Water is North Indian Deep Water 

 whose upper limit is considered to be the 27.6 o^ surface (S=35.1 °/oo, 

 T=6.5°C). Below about 2500 m are found Antarctic Circumpolar Water and 

 Antarctic Bottom Water. 



Station 22 (11° 04.8'N, 55^53. 9'E) (figure 25), located about 200 nmi to 

 the southeast of Socotra Island, is representative of the water found in the 

 Socotra Eddy. The T-S curve for this station lacks the variable salinity 

 structure found at stations taken further south and shows the influence of the 

 warm, saline Arabian Sea as reflected in its pronounced rightward displace- 

 ment. Persian Gulf Water is not evident at this station. Although there is 

 an extremely weak salinity maximum between 250 m and 300 m, it is not asso- 

 ciated with Persian Gulf Water which is centered at the 26.6 at surface. 

 Instead, this water with at values between 26.3 and 26.4, is formed in the 

 near-surface layers of the Gulf of Aden and the Arabian Sea; it is too light 

 to be associated with the Persian Gulf. The weak salinity minimum situated at 

 600 m near the 27.1 at surface is diluted Subtropical Subsurface Water. The 

 water underlying this weak salinity minimum is Red Sea Water with a high 

 saline core at about 800 m near the 27.3 at surface. Below 800 m, the T-S 

 curve is nearly coincident with the T-S curve at station 15. Water below 

 about 800 m is North Indian Deep Water underlain by Antarctic Circumpolar and 

 Bottom Waters. 



n 



