Impact of chlorophyll concentration on thermodynamics and dynamics in the tropical Indian ocean

It is well known that the physical properties of the ocean impact marine biological activity. Conversely, ocean biology feeds back to affect physical properties through the influence of phytoplankton on the ocean's absorption of incoming shortwave radiation. In this study, we explore this feedback in the tropical Indian Ocean (TIO) throughout the seasonal cycle by comparing solutions to a biophysical ocean model with and without chlorophyll concentrations. Phytoplankton-induced absorption increases near-surface temperature, thereby increasing evaporation and thinning the mixed layer. The resulting evaporation and restratification lower sea level and thereby affect circulation, particularly the summer monsoon current and the fall Wyrtki Jet. The circulation and evaporation changes in turn affect sea surface salinity. Finally, with chlorophyll there is a tendency for the model's sea-surface-temperature and mixed-layer depth-biases to shift closer to their observed values throughout the TIO, with the largest improvements occurring in the Arabian Sea and the Bay of Bengal.