Application of Satellite Products to Study Upwelling, Chlorophyll and Mixed Layer Depth of Southeastern Arabian Sea

Abstract

The role of wind stress in modulating upwelling and subsequent changes in mixed layer depth and chlorophyll concentration in southeastern Arabian Sea are studied for the period encompassing 2000–2008. During southwest monsoon season favoring upwelling in this region, it is observed that decrease in wind stress is always followed by an increase in chlorophyll concentration with approximately two weeks delay, accompanied by the shoaling of mixed layer depth, whereas the opposite is observed during high wind stress periods. This is attributed to the mixing and entrainment of nutrients into the euphotic zone which enable increase in surface chlorophyll and thereby boosting the primary productivity of the region. Wavelet analysis is used to deduce the temporal variability of winds, chlorophyll and mixed layer for the region. A time lag of 2 weeks is observed between the decrease in wind stress followed by a high in the surface chlorophyll concentration, often well captured by satellite. Another interesting observation is the bimodal variability of chlorophyll-a concentration during summer monsoon is observed in this region which was hitherto unnoticed. This spatial and temporal relation between wind, chlorophyll and mixed layer depth can provide valuable insight towards future studies on upwelling induced productivity for this region.