Signature of Mesoscale Eddies on Air-Sea Heat Fluxes in the North Indian Ocean

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 similar to 40 W m-2 k-1 for warm-core anticyclones (AEs) and similar to 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. The typical turbulent feature of the ocean surface, as depicted from satellite images, is often referred to as eddies that are crucial to the evolution of ocean states under climate change. With two data sources, both of which originate from satellite-based derivations, we investigate how mesoscale eddies (with spatiotemporal scales of similar to 100 km and similar to 1 month) contribute to air-sea heat exchanges and related processes in the North Indian Ocean. The seasonality of sea surface conditions is of great importance to behaviors and proportions of different eddy types in this region. Specifically, unconventional eddies, characterized as cold-core anticyclones and warm-core cyclones, are surprisingly active in the Arabian Sea and Bay of Bengal. This atypical feature implies that a thorough integration of dynamic and thermodynamic processes in understanding the ocean mesoscale is necessary. Eddy-induced SST-THF coefficient can approach similar to 40 and similar to 28 W m-2 k-1 for warm anticyclones and cold cyclones SSH-SST incoherent eddies (warm cyclones and cold anticyclones) are comparable in number to coherent/conventional eddies Seasonal variation of eddy compositions leads to monopolar, dipolar and canceled patterns of air-sea net fluxes