Incoming water from the Gulf of Oman flows along the northeastern side of the 

 strait. Judging from the surface isohalines for March, there is a limited amount 

 of surface outflow from the Persian Gulf, and this occurs along both sides of the 

 strait, extending well into the Gulf of Oman . The portion of the split flow that 

 moves along the Arabian coast appears to be the larger, as would be expected 

 from Emery's study . 



In an attempt to trace Persian Gulf water entering th« Arabian Sea, isoha- 

 lines of the secondary salinity maximum were plotted (Fig . 5). This maximum oc- 

 curs between 100 and 300 meters at all deep water stations in the study area . It 

 appears to stabilize at about 300 meters upon reaching the Arabian Sea except in 

 areas of bottom topographic highs where the maximuin is found at depths between 

 200 and 300 meters. Isohalines again show a forking of Persian Gulf water 

 near the Strait of Hormuz, and again the strongest outflow is along the Arabian 

 coast. Persian Gulf water can be clearly traced to about the mouth of the Gulf 

 of Oman . As previously stated, the secondary salinity maximum is affected by 

 bottom topography, and in fact, the isohalines outline the northern basin, moving 

 around high bottom features of the Murray Ridge . 



Bottom salinity measurements range from 34.44%ooff the Arabian coast in deep 

 water to 39.34%o in the Strait of Hormuz (Fig .6). In general, bottom water of the 

 Gulf of Oman and Arabian Sea basins does not exceed 35.00%o. Surface and bottom 

 salinities on the continental shelf are similar because of mixing. The exception is 

 in the Strait of Hormuz where bottom salinities exceed those of the surface by sig- 

 nificant amounts . 



C . Bottom Topography 



The bottom topography of the northern Arabian Sea, as constructed from H.O. 

 Charts 1587, 1588, and 1589, is illustrated in Figure 1 . The contour interval is 

 200 fathoms beginning at 100 fathoms. A clearer regional picture is presented in 

 the excellent physiographic diagram of the Indian Ocean by Heezen and Tharp 

 (1965 a, b) . 



The continental shelf is widest in the eastern portion of the area off India and 

 eastern Pakistan. Typically, the shelf here is 60 nautical miles wide and breaks at 

 depths ranging from 60 to 70 fathoms . Off the Gulf of Cambay it is over 150 miles 

 wide. Only one significant submarine canyon has been located in this area, the 

 "Swatch" near the mouth of the Indus . A report on the detailed sounding and delin- 

 eation of this feature has been made by Hayter (1960). The canyon is well devel- 

 oped to a depth of about 650 fathoms and is developed to a lesser extent to depths 

 of 900 fathoms . 



10 



