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Ablation of sloping ice faces into polar seawater

Published online by Cambridge University Press:  28 January 2019

Mainak Mondal Open the ORCID record for Mainak Mondal [Opens in a new window] ,
Bishakhdatta Gayen Open the ORCID record for Bishakhdatta Gayen [Opens in a new window] ,
Ross W. Griffiths Open the ORCID record for Ross W. Griffiths [Opens in a new window]  and
Ross C. Kerr
Mainak Mondal*
Affiliation:
Research School of Earth Sciences, The Australian National University, ACT 2601, Australia
Bishakhdatta Gayen*
Affiliation:
Research School of Earth Sciences, The Australian National University, ACT 2601, Australia
Ross W. Griffiths
Affiliation:
Research School of Earth Sciences, The Australian National University, ACT 2601, Australia
Ross C. Kerr
Affiliation:
Research School of Earth Sciences, The Australian National University, ACT 2601, Australia
*
†Email addresses for correspondence: mainak.mondal@anu.edu.au, bishakhdatta.gayen@anu.edu.au
†Email addresses for correspondence: mainak.mondal@anu.edu.au, bishakhdatta.gayen@anu.edu.au
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Abstract

The effects of the slope of an ice–seawater interface on the mechanisms and rate of ablation of the ice by natural convection are examined using turbulence-resolving simulations. Solutions are obtained for ice slopes $\unicode[STIX]{x1D703}=2^{\circ }{-}90^{\circ }$, at a fixed ambient salinity and temperature, chosen to represent common Antarctic ocean conditions. For laminar boundary layers the ablation rate decreases with height, whereas in the turbulent regime the ablation rate is found to be height independent. The simulated laminar ablation rates scale with $(\sin \unicode[STIX]{x1D703})^{1/4}$, whereas in the turbulent regime it follows a $(\sin \unicode[STIX]{x1D703})^{2/3}$ scaling, both consistent with the theoretical predictions developed here. The reduction in the ablation rate with shallower slopes arises as a result of the development of stable density stratification beneath the ice face, which reduces turbulent buoyancy fluxes to the ice. The turbulent kinetic energy budget of the flow shows that, for very steep slopes, both buoyancy and shear production are drivers of turbulence, whereas for shallower slopes shear production becomes the dominant mechanism for sustaining turbulence in the convective boundary layer.

JFM classification

Convection: Buoyant boundary layers Geophysical and Geological Flows: Ice sheets Turbulent Flows: Turbulent convection
Type
JFM Papers
Information
Journal of Fluid Mechanics , Volume 863 , 25 March 2019 , pp. 545 - 571
Copyright
© 2019 Cambridge University Press 

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