EGU General Assembly 2020
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Toward a new ice-shelf melt rate parameterization with large-eddy simulations

Carolyn Branecky Begeman, Xylar Asay-Davis, and Luke Van Roekel
Carolyn Branecky Begeman et al.
  • Fluid Dynamics and Solid Mechanics, Los Alamos National Laboratory, Los Alamos, New Mexico, United States of America (

Predictions of ice shelf melting depend on dynamical insights into ocean boundary layers below ice shelves. Fundamental questions regarding the nature of stratified turbulence below the sloped and ablating ice shelf base remain. Laboratory experiments, direct numerical simulations, and observations have yielded important insights, but have yet to produce a robust relationship between ice shelf melt rates and shear- and buoyancy-driven mixing. This relationship is the target of our Large-Eddy Simulations (LES) of the ice-shelf ocean boundary layer. Several new developments were applied to the LES code PALM to produce dynamic melting as well as tides. In this presentation, we demonstrate these new model capabilities. We contrast profiles of vertical turbulent fluxes of heat, salt and momentum across different simulated ice shelf settings: cold, shear-dominated settings vs. warm, buoyancy-dominated settings. We also discuss our recent work toward a new ice-shelf melt parameterization for use in large-scale ocean models on the basis of these simulations. A new melt parameterization is a critical component of ongoing ice-ocean coupling efforts, both to place melt rate predictions on a more physical footing and to achieve convergence with vertical ocean model resolution, on which current parameterizations fail.

How to cite: Begeman, C. B., Asay-Davis, X., and Van Roekel, L.: Toward a new ice-shelf melt rate parameterization with large-eddy simulations, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10848,, 2020

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Display material version 1 – uploaded on 30 Apr 2020
  • CC1: Comment on EGU2020-10848, Charles Pelletier, 03 May 2020

    Hi, thank you for the interesting presentation! I have two questions, but they're kind of related. Is the thickness of the ocean - ice BL one of the properties that significantly vary with buoyancy and pressure gradient, and if so, to which extent? For which vertical "far-field" distance from the actual interface is the BL parameterization (last slide) built and/or tested for?

    • AC1: Reply to CC1, Carolyn Begeman, 08 May 2020

      Charles, thank you for your questions. I anticipate that the BL thickness will significantly vary with buoyancy and the pressure gradient (insofar as it controls shear between BL and far-field flow). However, I can't speak to the magnitude of this dependence yet, pending results with the new turbulence closure. The BL parameterization as a function of far-field properties (as opposed to parameterization of vertical flux profiles) will likely be targeting the properties beyond the velocity BL, which tends to be the deeper than the scalar BL. However, this is something we'll have to test further in a regional ocean model. It's possible that we won't be able to achieve reasonable behavior without adopting a flux-profile approach.