Generation Mechanism Of Submesoscale Eddy In Arctic Marginal Ice Zone

With observations data and high resolution numerical model,two of the submesoscale eddy generation mechanisms,baroclinic instability and barotropic instability,were studied in the Arctic marginal ice zone.In the study of baroclinic instability mechanism,a submesoscale eddy was detected by SAR image in the summer marginal ice zone of Chukchi Sea and its genesis is related to front slump.Multiple reanalysis data suggested that the front was generated as a result of denser water transport.During front slumping,mean available potential energy converted into eddy available potential energy.Eddy available potential energy was in turn converted into eddy kinetic energy.Numerical simulations suggested that the eddy activity was determined by the total depth of the fronts instead of the mixed layer depth.However,if a strong pycnocline was added between the fronts,the vertical buoyancy gradient largely increased there,which reduced the growth rate of unstable energy.The eddy activity is not sensitive to water depth in the eddy genesis mechanism of baroclinic instability.The bathymetry and incident wavenumber(magnitude and propagation direction)are important for wave-driven current and mesoscale eddy genesis in barotropic instability mechanism.In a frazil-pancake ice zone,most of the wave energy is dissipated at the ice edge due to ocean-ice-wave interactions.As wave energy dissipated,energy was transferred into ice floe.Later,energy was in turn transferred into current.The wave propagation direction determines the velocity partition in the along-ice-edge and crossice-edge directions,which in turn determines the strength of jet.The wave dissipation rate increases with larger wavenumber,which enhances the jet strength and the strength of the mesoscale eddy,and vice versa.In shallow water,the jet may be largely dampened by bottom drag,and no visible mesoscale eddies are found.