Toward full ice sheet-ocean coupling in the Energy Exascale Earth System Model (E3SM)

Tuesday, December 11, 2018 - 08:00
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We present two aspects of our work toward fully coupling the Model for Prediction Across Scales - Ocean (MPAS-O) and MPAS-Albany Land Ice (MALI), both components of the Department of Energy’s Energy Exascale Earth System Model (E3SM). First, we present simulations with performed with monthly “offline” coupling. At each coupling interval, ice sheet geometry from MALI is used to produce a new ocean simulation mesh for MPAS-O. Then, prognostic variables from restart files are interpolated/extrapolated onto the new mesh in such a way that the simulation can continue from the modified restart file. This approach has been used successfully in other ice sheet-ocean models such as the Parallel Ocean Program-BISICLES model (POPSICLES). We present results from several Marine Ice Sheet-Ocean Model Intercomparison Project (MISOMIP) experiments, demonstrating the success of the offline coupling technique.

Second, we present ongoing work toward full, “online” coupling of MPAS-O and MALI through the E3SM coupler. This work includes implementation of: 1) a higher-order pressure gradient scheme, including a limiter to damp spurious flow in very thin layers; 2) a wetting-and-drying scheme allowing advance and retreat of the ice sheet grounding line; and 3) dynamic masking of both fluxes and state variables in the E3SM coupler based on the fraction of ocean and land ice in a cell as land ice and ocean boundaries move in time.

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