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 ∼2 mm/day along the southwest coast of Greenland. The above results are confirmed by the latest
projections from CMIP6 models.