More Frequent, Intense, and Extensive Rainfall Events in a Strongly Warming Arctic

The changes in the Arctic precipitation profoundly impact the surface mass balance of ice sheet and sea ice, the extent of snow cover, as well as the land/ice surface runoff in the Arctic, particularly when it occurs in liquid form. Here, we use state-of-the-art models from the Coupled Model Intercomparison Project Phase 5 to project the number of days with rainfall, the intensities and onset dates of rainfall events in the Arctic under the strong emission scenario (RCP8.5). The multi-model mean shows that rainfall will occur more frequently in the Arctic at the end of this century (2091-2100), with larger increase in the rainy days over the Pacific and Atlantic sectors (up to 12 days/month) during the cold seasons (October-May) and over the Arctic Ocean (up to 14 days/month) during the warm seasons (June-September) as compared with the present day (2006-2015). Greater uncertainty is found in the cold seasons, which mainly comes from the high variability among different models in the Norwegian Sea. Sixty-seven to ninety-three percentage of the increases in rainy days is contributed by the local warming and the remainder by the increase in total precipitation. Moreover, at the end of this century, the rainfall in spring will occur much earlier than the present day by more than 1 month, and the extent of rainfall will further expand toward the center of the Arctic Ocean and the inland Greenland in the future. The changes of rainfall intensity on the Arctic land area to the climate warming are more sensitive than that on the Arctic Ocean in warm seasons (May-September). The rainfall will be further strengthened in most of the Arctic continents in summer, with the largest increase in the intensity of similar to 2 mm/day along the southwest coast of Greenland. The above results are confirmed by the latest projections from CMIP6 models.