Modeling the thermal processes within the ice shelf–ocean boundary current underlain by strong pycnocline underneath a cold-water ice shelf using a 2.5-dimensional vertical slice model

Abstract

Oceanic melting beneath ice shelves is the main driver of the current mass loss of the Antarctic ice sheet. The resultant meltwater plumes influence the basal melting of ice shelves, and 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 dynamics and thermodynamics within these meltwater plumes, controlling the heat available for melting ice, remains outstanding. Here we investigate that important issue by developing a 2.5-dimensional nonhydrostatic vertical slice model with 1.5 m vertical resolution, and conduct 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 identify two dominating vertical thermal processes regulating the local temperature: the turbulent diffusion and the shear instabilities-induced convection (i.e., vertical advection), and carry 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, it is suggested 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 capture the interfacial processes between lighter–denser waters.