Role of Meso-Scale Eddies on Circulation in the South Eastern Arabian Sea in 2009

Abstract

Spatial current data were collected from South eastern Arabian Sea during July 2009 (summer monsoon) and December 2009 (winter monsoon) using the vessel mounted Acoustic Doppler Current Profiler (ADCP). During July 2009, observed ADCP currents were flowing southward along 75°E longitude with a complex pattern near the coast. During winter (December 2009), an anti-clockwise rotation of currents was observed in the study region, with its eastern arm along the southwest coast of India. The circulation pattern observed during the two seasons from ADCP measured data does not seem to follow any pattern described in climatology. To investigate this aspect, the geostrophic currents were computed utilizing the multi-mission altimeter sea surface height anomaly data for the corresponding months. The analysis of geostrophic currents indicates the presence of multiple eddies embedded in the Laccadive Low (LL) /Laccadive High (LH). Our present study shows that the meso-scale eddies embedded in the LL and LH play a significant role in deviating the observed circulation from climatology in this region. In addition, generating mechanisms of these eddies are addressed to substantiate our findings. The formation of these eddies is attributed to the local wind force during July 2009 and the enhanced baroclinic instability during December 2009.

Keywords:

• Eddies
• circulation
• Southeastern Arabian Sea
• Laccadive High
• WICC
• sea surface height anomaly

Acknowledgements

The authors are thankful to the director, NPOL, for his encouragement and motivation to carry out this study. The efforts of the commanding officer, officers, and crew of INS Sagardhwani in conducting the mission are gratefully acknowledged. We are grateful to the two anonymous reviewers for their valuable comments. We thank all the data providers for the data utilized in this study (AVISO, QuickStat, ASCAT).