Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 118, Issue 6, Pages -Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.2007541118
Keywords
ice-ocean interactions; double-diffusive convection; basal melting of Antarctic ice shelves; large-eddy simulation; thermohaline staircases
Categories
Funding
- Australian Research Council's Special Research Initiative for Antarctic Gateway Partnership [SR140300001]
- Australian Research Council Future Fellowship [FT180100037]
- Australian Antarctic Program Partnership
- Commonwealth of Australia
- Australian Research Council [FT180100037] Funding Source: Australian Research Council
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The study highlights the importance of double-diffusive convection in controlling ice shelf melt rates and oceanic mixed layer properties in warm and low-velocity cavity environments beneath ice shelves. The findings suggest that current ice-ocean parameterizations underestimate melt rates by neglecting the role of double-diffusive convection, which is identified as a primary process in the oceanic melting of ice shelves.
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.
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