Abstract
In the northern Arabian Sea, high salinity levels are primarily sustained by year-round evaporation, driving the convective formation of Arabian Sea High Salinity Water (ASHSW) during the winter monsoon (November – February). Although precipitation has largely been discounted as a critical controlling mechanism for winter convection, recent years have seen a notable increase in extreme cyclones over the Arabian Sea, particularly in post-monsoon cyclones (September – December) since 2014. However, the extent to which these cyclone-induced freshwater inputs disrupt the region's freshwater balance (evaporation – precipitation) and impact ASHSW formation remains unclear. Here, we present observational evidence supported by a suite of model simulation experiments, revealing a significant weakening in ASHSW formation triggered and sustained by extreme tropical cyclones. The addition of freshwater reduces the density of high-salinity water, augmenting stratification and disrupting the convective sinking process, ultimately limiting the depth of convective mixing. This strengthened stratification stabilizes the water column, exacerbating warming trends and destabilizing the freshwater balance between the Arabian Sea and the Bay of Bengal. These findings underscore the profound implications of extreme cyclone-induced freshwater inputs.