The influence of meso-scale eddies on the current field and thermal structure of the southeastern Arabian Sea

Abstract

Satellite altimetry in combination with ground-truth measurements and the Okubo–Weiss parameter-based eddy-tracking algorithm are used to study eddies in the southeastern Arabian Sea (SEAS) during the summer and winter of 2007 and 2008. In the SEAS, only the cyclonic eddy is present in summer whereas both cyclones and anticyclones are present in winter. These eddies, with dimensions of 60–120 km, propagate westward with slight north–south deflection at a speed of 5–23 cm s⁻¹ (mean 11.8 cm s⁻¹). The lifespan of eddies varies from two to six weeks. Exceptions are a cyclonic eddy in 2007 and an anticyclonic eddy in 2008 that persisted for 6 and 11 weeks, respectively. During summer and the early half of winter, wind-stress curl plays a significant role in the genesis of eddies in the SEAS. However, the propagation of these eddies is not influenced by wind-stress curl. Observations reveal that the thermal structure and currents are modified by these eddies. In winter, the signature of the cyclonic eddy is not prominent on the surface, as the water column is homogeneous up to 100 m. In the summer monsoon season, the signature of the eddy is evident up to the surface. During this period, the southward West India Coastal Current is modified locally by the cyclonic eddy formed in the SEAS.

Acknowledgements

The authors are grateful to the Director, NPOL, who gave encouragement and motivation to carry out this study. We gratefully acknowledge the Space Application Centre, Ahmadabad, for providing the necessary support.