Regimes and Transitions in the Basal Melting of Antarctic Ice Shelves

Rosevear, MG and Gayen, B and Galton-Fenzi, BK (2022) Regimes and Transitions in the Basal Melting of Antarctic Ice Shelves. In: Journal of Physical Oceanography, 52 (10). pp. 2589-2608.

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Abstract

The Antarctic Ice Sheet is losing mass as a result of increased ocean-driven melting of its fringing ice shelves. Efforts to represent the effects of basal melting in sea level projections are undermined by poor understanding of the turbulent ice shelf–ocean boundary layer (ISOBL), a meters-thick layer of ocean that regulates heat and salt transfer between the ocean and ice. To address this shortcoming, we perform large-eddy simulations of the ISOBL formed by a steady, geostrophic flow beneath horizontal ice. We investigate melting and ISOBL structure and properties over a range of free-stream velocities and ocean temperatures. We find that the melting response to changes in thermal and current forcing is highly nonlinear due to the effects of meltwater on ISOBL turbulence. Three distinct ISOBL regimes emerge depending on the relative strength of current shear and buoyancy forcing: “well-mixed,” “stratified,” or “diffusive-convective.” We present expressions for mixing-layer depth for each regime and show that the transitions between regimes can be predicted with simple nondimensional parameters. We use these results to develop a novel regime diagram for the ISOBL which provides insight into the varied melting responses expected around Antarctica and highlights the need to include stratified and diffusive-convective dynamics in future basal melting parameterizations. We emphasize that melting in the diffusive-convective regime is time dependent and is therefore inherently difficult to parameterize.

Item Type:	Journal Article
Publication:	Journal of Physical Oceanography
Publisher:	American Meteorological Society
Additional Information:	The copyright for this article belongs to American Meteorological Society.
Keywords:	Atmospheric thermodynamics; Boundary layers; Buoyancy; Glacial geology; Ice; Melting; Mixing; Sea level; Shear flow; Turbulence, 'current; Antarctic ice sheets; Antarctic ice shelves; Basal melting; Ice shelves; Large-eddy simulations; Mixing; Ocean boundaries; Salt transfer; Thick layers, Large eddy simulation
Department/Centre:	Division of Mechanical Sciences > Centre for Atmospheric & Oceanic Sciences
Date Deposited:	03 Jan 2023 10:35
Last Modified:	03 Jan 2023 10:35
URI:	https://eprints.iisc.ac.in/id/eprint/78674

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