Submesoscale dynamics are a key component of the global heat budget and they are crucial for heat transport between the ocean interior and the atmosphere. Submesoscale ocean processes play a significant role in the vertical transport of materials and heat. Therefore, how will submesoscale processes response to tropical cyclones (TCs) is worth studying. Based on in-situ measurement and high-resolution ocean numerical modeling, we investigated the role of submesoscale processes in the oceanic thermodynamic responses during TC Kalmaegi in the South China Sea (SCS).

Kalmaegi caused significant surface cooling, mixed layer deepening, and oscillating subsurface warm and cold anomalies. Submesoscale temperature variations within the mixed layer weakened after Kalmaegi, which is related to submesoscale heat transport. The mesoscale heat budget analysis revealed that the dominant thermal change in the upper ocean during Kalmaegi is vertical temperature advection, and the contribution of submesoscale processes is indispensable. Eddy-resolving sensitivity experiment demonstrated that the contributions of mesoscale and submesoscale processes to vertical heat transport during Kalmaegi were comparable. This study enhances our understanding of the multi-scale oceanic response to TCs.