Unusual Seasonal Variability of Submesoscale Dynamics in the Arabian Sea

Abstract Submesoscale processes in the ocean typically peak in winter, driven by mixed‐layer instability and intensified atmospheric forcing. However, coastal upwelling regions can deviate from this paradigm due to region‐specific dynamics. Based on validated high‐resolution simulations, we investigate the seasonal and regional variability of submesoscale activity in the Arabian Sea. Our results reveal that the western Arabian Sea exhibits a pronounced summer peak in submesoscale activity, primarily associated with wind‐driven upwelling, enhanced frontogenesis, and mixed‐layer baroclinic instability. Although earlier studies have reported intensification of submesoscale processes in coastal upwelling regions, detailed dynamical interpretations remain limited. Our work advances this understanding by explicitly diagnosing the regional physical mechanisms driving submesoscale variability under monsoon‐influenced upwelling system. This regional contrast becomes more evident when considering the broader basin. In the northern open ocean, submesoscale processes exhibit the canonical winter‐intensified pattern, whereas in the eastern Arabian Sea near the Maldives, they display a distinct bimodal structure with both summer and winter peaks. These findings highlight the importance of adopting region‐specific frameworks to interpret submesoscale seasonality, moving beyond the winter‐intensified paradigm dominant in open‐ocean settings. Our results provide novel insights into how coastal and open‐ocean submesoscale dynamics coexist in the Arabian Sea, with implications for seasonally varying energy cascades, vertical heat and nutrient fluxes, and air‐sea exchange in the upper ocean.