Spatiotemporal Features and Generation Mechanisms of Submesoscale Processes in the Low-Latitude Western Pacific Ocean

Abstract The spatiotemporal characteristics and generation mechanisms of submesoscale processes (SMPs) in the low-latitude western Pacific Ocean are investigated based on 1/30° Ocean General Circulation Model for the Earth Simulator (OFES) outputs and mooring measurements. Energetic submesoscale activities with the spatial and temporal scales shorter than 80 km and 20 days, respectively, are detected southeast of the Mindanao Island and north of the Halmahera Island along the paths of the Mindanao Current and Halmahera Eddy. Mooring observations indicate that the SMPs are intensified near the surface and can penetrate the thermocline down to 150 m. SMPs exhibit a significant seasonal cycle with high submesoscale kinetic energy (SKE) values in summer and autumn and relatively small SKE values in winter and spring. Barotropic instability associated with current–island interactions is the mechanism responsible for the generation and seasonal modulation of SMPs. This stands in contrast to the midlatitudes, where SMPs extract available potential energy through mixed layer baroclinic instability. Further energetic diagnostic analysis indicates that in the barotropic energy transfer chain, the mean kinetic energy is the main energy source for SKE. Mean kinetic energy contributes 65.6% of the kinetic energy to submesoscale processes, while the contribution of eddy kinetic energy is only 35.4%. Furthermore, the SKE budget results imply a route to energy dissipation via the forward energy cascade, which emphasizes the effects of SMPs on the diapycnal mixing in the low-latitude western tropical Pacific Ocean.