Mesoscale Eddies Modulate Mixed Layer Depth Globally

Mesoscale eddies, energetic vortices covering nearly a third of the ocean surface at any one time, modulate the spatial and temporal evolution of the mixed layer. We present a global analysis of concurrent satellite observations of mesoscale eddies with hydrographic profiles by autonomous Argo floats, revealing rich geographic and seasonal variability in the influence of eddies on mixed layer depth. Anticyclones deepen the mixed layer depth, whereas cyclones thin it, with the magnitude of these eddy-induced mixed layer depth anomalies being largest in winter. Eddy-centric composite averages reveal that the largest anomalies occur at the eddy center and decrease with distance from the center. Furthermore, the extent to which eddies modulate mixed layer depth is linearly related to the sea surface height amplitude of the eddies. Finally, large eddy-mediated mixed layer depth anomalies are more common in anticyclones when compared to cyclones. We present candidate mechanisms for this observed asymmetry.