Signature of mesoscale eddies on air-sea heat fluxes in the north Indian Ocean

Abstract

Using a combination of 20-year (1999–2018) remotely-sensed air-sea heat flux products and altimeter-based eddy atlas, we investigate the signature of mesoscale eddies on sea surface temperature (SST) and air-sea turbulent latent and sensible fluxes, or simply, turbulent heat fluxes (THFs), in the North Indian Ocean. On average, eddy-induced THF feedback can approach ∼40 W m−2 k−1 for warm-core anticyclones (AEs) and ∼28 W m−2 k−1 for cold-core cyclones (CEs) at their extreme values. In addition to these conventional SSH-SST coherent eddies and their imprints as monopoles in heat fluxes, a comparable proportion of SSH-SST incoherent eddies (cold-AEs and warm-CEs) are surprisingly active in this region, which offset the monopolar paradigm of coherent eddy-induced THF anomalies or develop a dipole structure when combined with these conventional eddies. In terms of seasonality, the aggregation of SSH-SST coherent and incoherent eddies in the Arabian Sea develops concentrated monopoles within eddy contours in both summer and winter, with a damped THF located farther away from the eddy core in winter. In the Bay of Bengal, a strong compensation between SSH-SST coherent and incoherent eddies is observed in summer that leads to null net fluxes, while the winter-time THF composite of these two eddy types displays a dipolar structure which was described as eddy-stirring effect in the literature.