Dual‐Pathway Influence of Submesoscale Processes on the Southern Ocean Meridional Overturning Circulation

Abstract The Southern Ocean meridional overturning circulation (MOC) play a crucial role in the global ocean water mass and heat redistribution, greatly modulating the earth climate variation. Although mesoscale eddies are known as an important component of the residual‐mean MOC that typically oppose wind‐driven Eulerian overturning, the contribution of submesoscale processes remains poorly understood. Based on high‐resolution simulations (1/48° and 1/24°), we decompose the residual MOC streamfunction into large‐, meso‐, and submesoscale components and reveal dual‐pathway impact of submesoscale processes. Specifically, the directly resolved submesoscale transport accounts for 18%–22% of the mesoscale anticlockwise overturning, and the amplification of mesoscale transport via submesoscale inverse energy cascade indirectly generates an additional enhancement of 24%–28%. Such a dual‐pathway impact, which is not resolved by climate models, exerts a substantial modification on the residual‐mean MOC, indicating that submesoscale dynamics are critical to the Southern Ocean MOC and call for reasonable parameterization in the future.