104 / 2023-07-30 20:42:13

Asymmetry of Submesoscale Instabilities in Anticyclonic and Cyclonic Eddies

mesoscale eddy,submesoscale,asymmetry

Previous studies suggested that anticyclonic flows are more vulnerable to submesoscale instabilities than cyclonic flows. Nevertheless, satellite altimetry observations of mesoscale eddy activities indicate that eddies with long lifetimes and large propagation distances are preferred to be anticyclonic. Here we use Massachusetts Institute of Technology general circulation model (MITgcm) to investigate the asymmetries of submesoscale instabilities in anticyclonic and cyclonic eddies. Submesoscale-resolving numerical simulations reveal a distinct distributional difference of submesoscale instabilities in the anticyclone and cyclone: submesoscales appear actively at peripheries of the anticyclone but tend to be confined to the central area of the cyclone. Moreover, the mean-to-eddy energy conversions also show prominent differences within the anticyclone and cyclone. We further clarify that the evolution of mesoscale eddy is likely the primary reason for the asymmetries of submesoscale instabilities in anticyclone or cyclone. The center-around submesoscale instabilities within cyclonic eddies tend to significantly change the thermal structure and flow field, and eventually lead to eddy breakup. On the contrary, anticyclone would maintain its thermal structure and live a longer lifetime as the submesoscale instabilities would disperse to the peripheries.