Anomalous circulation in the eastern equatorial Indian Ocean during southwest monsoon of 1994

Abstract

Geostrophic circulation derived from hydrographic data collected during July-August, 1994 along 80, 84 and 88E between 5N and 3S latitudinal belt in the eastern equatorial Indian Ocean is presented. A broad westward flow north of the equator and an eastward flow, constituting the southwest monsoon current (SWMC), in the vicinity of the equator characterise the upper ocean circulation. While low salinity waters (33.5 -34.75) in the upper layer are advected westward from 88 E via the westward flow, the Arabian Sea High Salinity Water is advected eastward via the SWMC in the depth interval of 75-100 m. Strong (1.0-2.5 m/s) westward current is present in the upper 50 m at 1.25N at all the longitudes. Eastward flowing undercurrent is present north of the equator below 100 m depth whose velocity and depth are maximum (0.5 m/s and 150 m respectively) between 1.0-1.5N belt along 80 E. The surface wind field during the southwest monsoon of 1994 is anomalous and the surface layer circulation north of the equator does not appear to be wind-driven. The possible influence of remote forcing in driving the circulation is discussed.