The coastal current off western India during the northeast monsoon

Abstract

Hydrographic data collected during December 1987 and January 1988 are used to describe the poleward coastal current along the west coast of India that flows against weak winds during the northeast monsoon. Near the southern end of the coast, at about 10 degrees N, the current was approximately 400 km wise, 200 m deep and carried the low salinity Equatorial Surface Water. The isopycnals tilted down on approaching the coast. Near the northern end of the coast, at about 22 degrees N, the flow was restricted mainly to the vicinity of the continental slope; the current was a narrow (100 km), 400m deep jet with a transport of about 7 x 106 m3 s-1. Along most of the coastline, a southward moving undercurrent was inferred from the distribution of salinity, temperature and dynamic topography. To understand the driving mechanism of the current, the annual cycle of the contribution of the longshore pressure gradient and that of the winds to the near-surface momentum balance was examined using available climatologies.