Eddies in the Indian Ocean

Abstract

This chapter is concerned with that part of the Indian Ocean north of about 20°S. Most of the area, from about 10°S northwards, comes under the influence of the monsoons and has a strongly variable seasonal circulation. As in most parts of the ocean, the only available overall view of eddy properties in this region is the one provided by Wyrtki, Magaard and Hager (1976). They calculated eddy kinetic energy per unit mass for each 5° square of the world’s oceans, using all available ships’ drift observations of surface current. In the Indian Ocean, their values of eddy kinetic energy are relatively high - over 1000 cm2s−2 along most of the equator, and over 2000 off Somalia; nowhere north of 10°S is the eddy kinetic energy less than 600 cm2s−2. Before attempting to compare eddies in this region with those in others, we need to estimate how much of this energy is related to the seasonal changes in circulation. In doing this, some characteristic subsections of the region will be identified, and in the rest of the chapter the eddy properties of each of these subsections will be briefly described.