Water masses and patterns of flow in the Somali Basin during the southwest monsoon of 1964

Abstract

Closely spaced hydrographic sections made during August–September 1964 in latitudes 3°S–12°N, and between the East African coast and longitude 56°E, define in detail a complex structure of water masses in the Somali Basin under the southwest monsson. Reference to observations made elsewhere in the Indian Ocean permits clear identification of the source waters responsible for this structure. In the near-surface water the distributions of temperature and salinity show the course and lateral extent of the Somali Current, the offshore movement of cold water upwelled near the Somali coast, and two warm saline inflows from the Gulf of Aden and the Arabian Sea. At depths greater than 2000 m, small differences in temperature-salinity characteristics reveal a narrow northward flow adjacent to the continental slope, roughly paralleling the Somali Current. No definite inferences can be drawn concerning flow patterns at intermediate depths, both because of the apparent small scale of horizontal variation there, which is not resolved by the station spacing, and because of inherent ambiguity in core methods when applied to flows which may reverse seasonally.