Interannual Variations of Submesoscale Circulations in the Subtropical Northeastern Pacific

Impacts of oceanic submesoscale circulations on oceanic circulation as well as marine ecosystem and air-sea heat flux have been reported by recent studies. Therefore, their regionality and variations on various timescales are important to understand their impacts. The submesoscale circulations are active in winter, which is mostly enhanced by mixed layer instability (MLI). However, their variations on timescales longer than interannual are not well understood. This study shows the interannual variations of active submesoscale circulations in winter and their mechanism in the subtropical northeastern Pacific using the output of a submesoscale permitting simulation. The submesoscale kinetic energy varies synchronously with the available potential energy release in a process of MLI. El Niño events appear to modulate the interannual variations. In addition, the similarities and differences between the variations in the eastern and western subtropics are highlighted.