that is separate from and considerably smaller than the Great Whirl (about 

 200 nmi). 



Section 8 (figure 13), taken between 30 and 31 August, shows extended 

 coverage of the eastern edge of the Socotra Eddy. The downslope of isotherms 

 out to 100 nmi indicates a frontal zone accompanied by strong vertical shear. 

 This front is probably the boundary between the northern edge of the Socotra 

 Eddy and the Gulf of Aden/Arabian Sea circulation system. The gradual rise of 

 isotherms between 100 and 200 nmi is indicative of southwesterly flow around 

 the eastern extremity of the Socotra Eddy; Arabian Sea water may be entrained 

 into the Socotra Eddy. The downslope of isotherms in the last 80 nmi of the 

 section is an indication that the section has crossed the front separating the 

 Socotra Eddy from the Arabian Sea. 



Section 9 (figure 14) was made to recross the Great Whirl to assess any 

 changes that may have occurred during the decay of the southwest monsoon and 

 was taken between 31 August and 2 September. Pronounced upslope of isotherms 

 is seen between 390 and 320 nmi from the end of the section. The 25°C isotherm 

 rises from 103 m to about 10 m within 30 nmi between 390 and 360 nmi from the 

 end of the section. Similarly, the 20°C isotherm rises from 150 m to 70 m 

 between 390 and 320 nmi from the end of the section. This pronounced upslope 

 of isotherms occurs across the front between the equatorial and coastal water 

 of the Great Whirl and the warm (T>26°C), saline (S>35.9 °/oo) water to the 

 east that is of Arabian Sea origin. Sea surface salinities across this front 

 decrease from 35.9 °/oo to 35.5 °/oo proceeding from east to west (figure 19). 

 Between 320 and 200 nmi from the end of the section the isotherms exhibit a 

 gradual slope downward toward the west. Within this horizontal distance of 

 120 nmi the 20^0 isotherm deepens from 70 m to 140 m. The depth analysis of 

 the 20°C isotherm (figure 30) indicates that this deepening of the isotherms 

 is associated with the southeast corner of the Socotra Eddy. High sea surface 

 salinities (S>35.8 °/oo) (figure 19) are collocated with the deepening iso- 

 therms in this area and thus are a further indication of the presence of water 

 of Arabian Sea origin. Between 200 and 100 nmi from the end of the section a 

 pronounced peaking of isotherms is observed. The 25°C isotherm breaks the 

 surface between 140 and 160 nmi from the end, and the 20°C isotherm shoals 

 from 140 to 60 m between 200 and 120 nmi from the end of the section. The 

 minimum in the depth field of the 20°C isotherm (figure 30) reveals that this 

 shoaling of isotherms is associated with the boundary between the Great Whirl 

 and the Socotra Eddy. The last 120 nmi of this section is characterized by 

 pronounced deepening of the isotherms. The 20°C isotherm deepens from 60 m to 

 about 230 m for the last 120 nmi of the section. The analysis of the depth of 

 the 20OC isotherm (figure 30) further reveals that this westward deepening of 

 isotherms is connected with the anticyclonic center of the Great Whirl. 

 Unfortunately, before the section could be completed with an approach to the 

 coast, an employee became ill, and a direct track had to be steamed back to 

 the Seychelles. 



Section 10 (figure 15), taken from 2 to 4 September, was made to steam a 

 direct track to the Seychelles. This section follows the southern half of the 

 Great Whirl, as indicated by a sharp upward slope of isotherms to the south. 

 It is interesting to note that the depth interval between the 240C and 22^0 

 isotherms decreases from 96 m at a location 500 nmi from the end of the section 

 to 6 m at 250 nmi from the end of the section. The packing of isotherms along 



