Ice base slope effects on the turbulent ice shelf-ocean boundary current

Abstract

The majority of Antarctica’s contribution to sea level rise can be attributed to changes in ocean-driven melting at the base of ice shelves. Turbulent ocean currents and melting are strongest where the ice base is steeply sloped, but few studies have systematically examined this effect. Here we use 3-D, turbulence-permitting large-eddy simulations (LES) of an idealised ice shelf-ocean boundary current to examine how variations in ice base slope influence ocean mixing and ice melting. The range of simulated slope angles is appropriate to the grounding zone of small Antarctic ice shelves and to the flanks of relatively wide ice base channels, with far-field ocean conditions representative of warm-water ice shelf cavities. Within this parameter space, we derive formulations for the friction velocity, thermal forcing, and melt rate in terms of total melt-induced buoyancy input and ice base slope. This theory predicts that melt rate varies like the square root of slope, which is consistent with the LES results and differs from a previously proposed linear trend. With the caveat that further simulations with an expanded range of basal slope angles and ocean conditions would be necessary to evaluate the validity of our conclusions across the full Antarctic ice base slope parameter space, the derived scalings provide a potential framework for incorporating slope-dependence into parameterisations of mixing and melting at the base of ice shelves.