Equatorial Jet - A case study

Abstract

Detailed EOF analysis of wind data reported by Wunsch over Gan(00-degrees-41'S; 73-degrees-10'E) is made for the period 1963-70. Mean monthly wind pattern over these years shows one significant peak each in pre and postmonsoon transition periods. The year 1964, which exhibited least variability from mean wind structure, has been chosen for the case study. EOF analysis of hydrographic data of 1964 is also carried out to understand the response signature of water column to prevailing westerlies. A jet forms in the central Indian Ocean, which gathers momentum as it advances eastward. Sinking of the thermocline and formation of a subsurface high salinity core are, apparently, manifestations of vertical advection of momentum associated with the jet. The driving force behind the equatorial undercurrent in the Indian Ocean ceases to exist in May, causing undercurrent to rebound at east coast and produce an opposite flow at the subsurface depth. Absence of a high salinity core during May-June may be accounted for by enhanced mixing at equator arising out of shear produced at the boundary of 2 opposing currents.