Artical Figures and Data (VHF)

Vertical heat flux (VHF) in the ocean is a key process that regulates surface temperature and influences regional climate patterns. In the Arabian Sea, seasonal monsoon winds dramatically alter ocean circulation and heat distribution. Our high-resolution simulations show that small-scale motions, called submesoscale dynamics, become especially active during summer, driving heat upward from below the surface. These processes contribute significantly to moving heat in the upper ocean, sometimes exceeding the influence of mesoscale eddies. In winter, however, this upward heat movement weakens or reverses, with some regions showing downward heat flow. This seasonal shift is driven not only by weaker winds and frontal structures but also by salt-finger convection, which pulls heat downward. These results highlight how small-scale ocean dynamics, working in tandem with monsoon cycles, can reshape the direction and strength of heat movement, key for understanding ocean-atmosphere interactions and predicting regional climate change.