| Summary: | Ice shelf basal melting is the major cause of the current mass loss of Antarctic ice sheets. The resultant meltwater plumes contribute to the development of the unique two-layer stratified ice shelf–ocean boundary currents underlain by warmer, saltier, and stationary source waters. However, knowledge of the thermodynamics within these plumes, controlling the heat available for melting ice, remains outstanding. To this end, we investigated that important issue by developing a 2.5-dimensional nonhydrostatic vertical slice model with 1.5 m vertical resolution, and conducted the reference run based on a representative Ice Shelf Water (ISW)-High Salinity Shelf Water (HSSW) boundary current beneath the Amery Ice Shelf, East Antarctica. Based on that we identified two dominating vertical thermal processes regulating the local temperature: the turbulent diffusion and the shear instabilities-induced convection, and carried out a quantitative thermal budget analysis in the framework of plume model, including deriving an analytical expression for the entrainment-induced heat flux. Moreover, after evaluating the entrainment parametrizations, we found that the common assumption of neglecting the velocity at the lower boundary of meltwater plume potentially leads to a considerable deviation from the real entrainment. The sensitivity of the simulated results to model configuration and model resolution are also investigated. The findings in this study imply that we need to improve the model resolution of current ocean cavity models to sufficiently resolve the interfacial processes between lighter–denser waters.
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