Seasonal and inter-annual variability of Chlorophyll–a in the Arabian Sea from SeaWiFS data

Abstract

This study utilizes monthly mean chlorophyll–a concentration (Chl–a) and sea surface temperature (SST) retrieved from Sea-viewing Wide Field-of-view Sensor (SeaWiFS) and Advanced Very High Resolution Radiometer (AVHRR) respectively. In addition surface wind vector derived from SeaWinds observations were used in this study. The Chl–a and the SST data for the period September 1997 to August 2007 were used in the present study. Whereas the wind vector for the period August 1999 to August 2007 is used. The seasonal and inter-annual variations in the Chl-a and SST in the Arabian Sea warm pool region were clearly observed. The winter bloom signatures were seen in the month of February. One interesting result obtained from the study is, post 2002 period shows Chl–a maxima in the month of September. High inter-annual variation in Chl–a and SST were observed during south–west monsoon months after 2002. The effects of wind stress and SST on the Chl–a are studied. It is found that the relation between wind stress induced divergence/convergence of the ocean surface (Cov/Div) and Chl–a is stronger than that of SST. Exceptionally high anomalous Chl–a was observed during 2004 and 2006 summer monsoon period due to increased Cov/Div and low SST during these periods.