Upper ocean variability of the equatorial Indian Ocean and its relation to chlorophyll pigment concentration.

Abstract

Hydrographic data from the upper ocean together with atmospheric data and satellite data are used to understand the variability of upper ocean and its relation to surface chlorophyll in the Equatorial Indian Ocean. The sea surface temperature showed a strong semi-annual signal with peak warming in April and cooling in July-August. Both mixed layer depth (MLD) and barrier layer thickness (BLT) showed a weak annual signal. The deep MLD during summer was due to the combined effect of strong winds and low net heat flux while shallow MLD in winter was driven by weak winds and net precipitation. A strong correlation of chlorophyll with SST was seen in the western EIO compared to central and eastern EIO. Our study indicated that the lack of seasonality in the chlorophyll pigment concentration, away from the western boundary, arises due to the lack of processes that could supply nutrients from subsurface.