Abstract
Abstract. The physical interactions between ice sheets and their surroundings are major factors in determining the state of the climate system, yet many current Earth system models omit them entirely or approximate them in a heavily parameterised manner. In this work we have improved the snow and ice sheet surface physics in the FAMOUS climate model, with the aim of improving the representation of polar climate and implementing a bidirectional coupling to the Glimmer dynamic ice sheet model using the water and energy fluxes calculated by FAMOUS. FAMOUS and Glimmer are both low-resolution, computationally affordable models used for multi-millennial simulations. Glaciated surfaces in the new FAMOUS-ice are modelled using a multi-layer snow scheme capable of simulating compaction of firn and the percolation and refreezing of surface melt. The low horizontal resolution of FAMOUS compared to Glimmer is mitigated by implementing this snow model on sub-grid-scale tiles that represent different elevations on the ice sheet within each FAMOUS grid box. We show that with this approach FAMOUS-ice can simulate relevant physical processes on the surface of the modern Greenland ice sheet well compared to higher-resolution climate models and that the ice sheet state in the coupled FAMOUS-ice–Glimmer system does not drift unacceptably. FAMOUS-ice coupled to Glimmer is thus a useful tool for modelling the physics and co-evolution of climate and grounded ice sheets on centennial and millennial timescales, with applications to scientific questions relevant to both paleoclimate and future sea level rise.
Highlights
Continental-scale ice sheets are one of the primary components in the Earth’s climate system
In this paper we describe modifications that we have made to the physics and tiling in the land surface of FAMOUS to produce a configuration called FAMOUS-ice, and we show that the results are scientifically useful within the context of coupling to a model of the Greenland ice sheet (GrIS)
We found a range of values [0.006–0.008] μm− 2 for asnow,visible that all allow FAMOUS-ice to match the modern state of the GrIS but which produce different large-scale sensitivities of the ice sheet to changes in climate
Summary
Continental-scale ice sheets are one of the primary components in the Earth’s climate system. Many of the physical processes that are key to modelling the surface physics of polar regions are not well captured by models that are intended for global use, such as stable polar boundary layers, katabatic winds, or multi-year snowpacks (Connolley and Bracegirdle, 2007) For all these reasons, the majority of AOGCMs do not include interactive ice sheets and omit much of the physics required to directly model boundary conditions for ice sheet models. Building on FAMOUS’s climate simulation and a framework for sub-grid-scale modelling within its land surface scheme, we decided to improve FAMOUS’s representation of ice sheet surface physics and to directly couple water and energy fluxes between FAMOUS and the ice sheet model. A scientific application of FAMOUS-ice, looking at the future stability of the Greenland ice sheet, is published separately (Gregory et al, 2020)
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