On dynamics of vertical eddy heat transport
Simulations results reveal low coherence (<0.3) between eddy vertical velocity and temperature anomalies in the upper 100 m, suggesting that bulk of the eddy motions is irrelevant to the vertical heat transport. The generalized SG-Omega equation shows good skills in reproducing the eddy vertical velocity anomalies responsible for the vertical heat transport. Frontogenesis and vertical friction are found to be the two dominant mechanisms generating the vertical eddy heat transport. By destructing the vertical geostrophic shear, the latter induces a secondary circulation that acts to restore the geostrophic balance and transport heat upwards.
The vertical eddy heat transport in the upper ocean is strongly modulated by atmospheric synoptic variabilities, exhibiting pronounced enhancement under strong surface cooling associated with intense winter storms. This enhancement is mainly attributed to the intensified vertical mixing and negative surface wind power on eddies that promote the vertical friction effect.