The intermediate salinity maximum at station 5 between 500 m and 600 m 

 depth is yery weak (S=35.10 °/oo to 35.15 °/oo) and is centered about the 

 27.1 a^ surface. It is Red Sea Water advected by very weak southwesterly- 

 setting currents below 500 m. This salinity maximum is underlain by a second, 

 slightly stronger (S>35.25 °/oo) salinity maximum at stations 3 and 4 between 

 700 m and 900 m depth. The stronger salinity maximum ts likewise the result 

 of entrainment of Red Sea Water into the deep southwesterly-setting currents 

 below 500 m and is centered between the 27.2 o^ and 27.3 a^ surfaces. Between 

 about 1000 m and 1500 m the salinity decreases steadily with depth. This 

 water between about 1000 m and 1500 m has been termed by Warren et al_. (1966) 

 North Indian Deep water and has characteristics of Antarctic Circumpolar water 

 which is found at the surface at about 50°S throughout the Southern Ocean. 

 This water has a a^ value of about 27.6. 



Figure 38 shows geostrophic currents (cm sec"^ ) relative to 1500 dbar 

 along section 2. This section crosses the center of the Great Vihirl and 

 reveals the anti-cyclonic surface and near-surface circulation indicated in 

 the dynamic topography charts (figures 32, 33, and 34). Northeasterly-setting 

 currents are again strongest in the near-surface levels immediately adjacent 

 the coast where cold coastal water produces the trough in the dynamic topogra- 

 phy. Surface and near-surface geostrophic currents set northeasterly out to 

 station 11 (5° 34.4'N, 53° 20.9'E). Between stations 11 and 13 (6° 17.1 'N, 

 57° 38.9' E) the currents become southwesterly-setting down to 1500 m. Between 

 stations 8 (4° 29.1 'N, 49° 26.8'E) and 9 (4° 40.8'N, 50° 29.7'E) below 150 m 

 the currents become southwesterly-setting indicating a change from the anti- 

 cyclonic circulation in the upper layers of the Great Whirl to what appears to 

 be cyclonic circulation in the lower layers. This reversal in circulation is 

 suggested in the chart of the dynamic topography of the 500 dbar surface 

 relative to 1500 dbar (figure 35). 



The salinities associated with section 2 (figure 39) again indicate the 

 extremely complex and irregular salinity structure of the upper and mid-depths 

 of the northwestern Indian Ocean. There are essentially three subsurface 

 salinity maxima evident along section 2, each associated with its own forma- 

 tion area. The shallowest salinity maximum (S>35.40 /oo) is found between 

 100 m and 200 m and is centered about the \iery strong near-surface pycnocline 

 between the 24.0 04. and 26.0 a*, surfaces. This water originates in the near- 

 surface layers of the Arabian Sea, an area of intense solar insolation, 

 evaporation, and wind mixing. The next salinity maximum is found between 

 250 m and 400 m at stations 10, 11, 12, and 13. The water in this salinity 

 maximum (S>35.30 °/oo) is centered between the 26.0 cr^ and 26.9 Of surfaces 

 and is characteristic of water originating in the Persian Gulf, the deepest 

 salinity maximum (S>35.25 /oo) is most pronounced at station 10 and is cen- 

 tered at approximately 800 m depth. Being centered about the 27.3 a^ surface, 

 this water is characteristic of Red Sea Water. 



Figure 40 presents geostrophic currents (cm sec"l ) along section 4 cal- 

 culated relative to 1500 dbar. This section taken from 23 to 26 August 1979 

 was made to traverse the northern edge of the Great Whirl and to assess the 

 area of maximum upwelling south of Ras Hafun. The currents in this section 

 are northeasterly with the exception of weak southwesterly flow between 

 stations 13 and 14. Owing to the long distance between stations 13 and 14 

 current values based on dynamic height differences between them are probably 



15 



