Elmer/Ice News

On the nature of melt-rate oscillations in coupled ice-ocean simulations

An emergent feature in several contributing coupled models to the 1st Marine Ice Sheet–Ocean Model melt rate evolution of timeIntercomparison Project (MISOMIP1) was a time-varying oscillation in basal melt rates. In this study, the authors used Elmer/Ice coupled to ROMSIceShelf via the Framework for Ice-Sheet Ocean Coupling (FISOC) to investigate the origin and implications of this observed feature and, more generally, the impact of coupled modeling strategies on the simulated basal melt in an idealized ice shelf cavity based on the MISOMIP setup. Interestingly, melt oscillations emerged in both, the coupled system and the standalone ocean model using a prescribed change of cavity geometry. There appears a close relation to the discretized ungrounding of the ice sheet, probably strengthened by a combination of positive buoyancy–melt feedback and/or melt–geometry feedback near the grounding line, and the frequent coupling of ice geometry and ocean evolution. There is still debate whether this is purely numerical or a numerical artifact enhanced by model physics. The paper includes a short best-practice guide on the choice of parameters to minimize the impact of this effect.

Read more: Zhao, C., R. Gladstone, B.K. Galton-Fenzi, D. Gwyther, and T. Hattermann, 2022. Evaluation of an emergent feature of sub-shelf melt oscillations from an idealized coupled ice sheet–ocean model using FISOC (v1.1) – ROMSIceShelf (v1.0) – Elmer/Ice (v9.0),. Geosci. Model Dev., 15, 5421–5439, doi:10.5194/gmd-15-5421-2022

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