Past and future of the Arctic sea ice in HighResMIP climate models
Abstract. We examine the past and projected changes in Arctic sea ice properties in 6 climate models participating in the High Resolution Model Intercomparison Project (HighResMIP) in the Coupled Model Intercomparison Project Phase 6 (CMIP6). Within HighResMIP each of the experiments are run using a reference resolution configuration (consistent with typical CMIP6 runs) and higher resolution configurations. The role of horizontal grid resolution in both the atmosphere and ocean model components in reproducing past and future changes in the Arctic sea ice cover is analysed. Model outputs from the coupled historical (hist-1950) and future (highres-future) runs are used to describe the multi-model, multi-resolution representation of the Arctic sea ice and to evaluate the systematic differences (if any) that resolution enhancement causes. Our results indicate that there is not a strong relationship between the representation of sea ice cover and the ocean/atmosphere grid: the impact of horizontal resolution depends rather on the examined sea ice characteristic and the model used. However, the refinement of the ocean grid has a more prominent effect compared to the atmosphere: eddy-permitting ocean configurations provide more realistic representations of sea ice area and sea ice edge. All models project substantial sea ice shrinking: the Arctic loses nearly 95 % of sea ice volume from 1950 to 2050. The model selection based on historical performance potentially improves the accuracy of the model projections and predicts the Arctic to turn ice-free as early as in 2047. Along with the overall sea ice loss, changes in the spatial structure of the total sea ice and its partition in ice classes are noticed: the marginal ice zone (MIZ) dominates the ice cover by 2050 suggesting a shift to a new sea ice regime much closer to the current Antarctic sea ice conditions. The MIZ-dominated Arctic might drive developments and modifications of model physics and parameterizations in the new generation of GCMs.
Status: final response (author comments only)
Viewed (geographical distribution)