Impact of Rossby waves on chlorophyll variability in the southeastern Arabian Sea

We use remotely sensed ocean colour data to show that Rossby waves are associated with the westward migration of chlorophyll distribution patterns in the southeastern Arabian Sea (SEAS). During the winter monsoon (November–February), the high chlorophyll concentrations observed along the west coast of India and Sri Lanka drifts westwards along with the downwelling Rossby waves. The speed of these chlorophyll signatures is in rough agreement with the expected second baroclinic mode Rossby wave speed. Observations from Ocean Surface Currents Analyses Real-time (OSCAR) suggest that it is the geostrophic currents associated with the Rossby wave propagation that influences the surface chlorophyll concentrations in the SEAS. The westward migration of chlorophyll is weaker during the summer monsoon (June–September) when the upwelling Rossby wave is observed in the sea-level data.