HAMSOM-VICE v0.9: Comparison of two variable ice-ocean drag coefficient parameterizations on annual simulations of Bohai Sea ice

Abstract. This study compares the simulation performance of two ice-ocean drag coefficient parameterizations (Scheme1 (original scheme): large-scale roughness parameterization, Scheme2 (newly introduced scheme): small-scale geometric roughness parameterization) for the Bohai sea ice in the 2011/2012 ice season, revealing main component of the ice-ocean drag coefficient (C_dw) and its crucial regulatory role in sea ice dynamic-thermodynamic processes in the Bohai Sea. The findings demonstrate that, for the ice-ocean drag in the thin ice environment of the Bohai Sea, the ice-bottom surface skin drag and the ice floe edge form drag dominate, while the contribution of ice keel-related drag is negligible due to insufficient ice thickness (averaging 20–30 cm). Scheme2 reduces the root mean square error (RMSE) of daily total ice area by 28 % compared to the Scheme1, showing higher simulation accuracy in the overall spatiotemporal ice evolution in the Bohai Sea. While Scheme1 demonstrates closer agreement with the observed length of ice season (underestimating by only 7 days). The result analysis of key sea ice variables and ice-ocean interfacial variables indicates that C_dw can affect the ice velocity through the dynamic feedback mechanism, and the basal freezing/melting through the thermodynamic dual feedback mechanisms.