The role of double-diffusive convection in basal melting of Antarctic ice shelves

Rosevear, MG and Gayen, B and Galton-Fenzi, BK (2021) The role of double-diffusive convection in basal melting of Antarctic ice shelves. In: Proceedings of the National Academy of Sciences of the United States of America, 118 (6).

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Abstract

The Antarctic Ice Sheet loses about half its mass through ocean-driven melting of its fringing ice shelves. However, the ocean processes governing ice shelf melting are not well understood, contributing to uncertainty in projections of Antarctica's contribution to global sea level. We use high-resolution large-eddy simulation to examine ocean-driven melt, in a geophysical-scale model of the turbulent ice shelf-ocean boundary layer, focusing on the ocean conditions observed beneath the Ross Ice Shelf. We quantify the role of double-diffusive convection in determining ice shelf melt rates and oceanic mixed layer properties in relatively warm and low-velocity cavity environments. We demonstrate that double-diffusive convection is the first-order process controlling the melt rate and mixed layer evolution at these flow conditions, even more important than vertical shear due to a mean flow, and is responsible for the step-like temperature and salinity structure, or thermohaline staircase, observed beneath the ice. A robust feature of the multiday simulations is a growing saline diffusive sublayer that drives a time-dependent melt rate. This melt rate is lower than current ice-ocean parameterizations, which consider only shear-controlled turbulent melting, would predict. Our main finding is that double-diffusive convection is an important process beneath ice shelves, yet is currently neglected in ocean-climate models. © 2021 National Academy of Sciences. All rights reserved.

Item Type:	Journal Article
Publication:	Proceedings of the National Academy of Sciences of the United States of America
Publisher:	National Academy of Sciences
Additional Information:	The copyright of this article belongs to National Academy of Sciences
Department/Centre:	Division of Mechanical Sciences > Centre for Atmospheric & Oceanic Sciences
Date Deposited:	04 Mar 2021 10:44
Last Modified:	04 Mar 2021 10:44
URI:	http://eprints.iisc.ac.in/id/eprint/68094

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