Comparison of Future Precipitation changes between CMIP5 and CMIP6

Abstract:

Future Arctic climate projections largely centers on the expected continuing increase in temperature and decline in sea ice, however large increases in precipitation are also expected by the end of the century. This is significant in the Arctic, as most of this increase is due to a change in precipitation type with most regions expected to get more rainfall than snowfall, however there is a great range of uncertainty in this. To try and provide more clarity, we explore these precipitation changes in latest coupled model inter-comparison project (CMIP6) and compare this to CMIP5 to determine if these new modelling experiments project significant differences.

In line with CMIP5, CMIP6 also simulates a large increase in precipitation across the entire Arctic in all seasons by the end of the century. Both experiments also largely agree that most of this change will be the result of increased rainfall. CMIP6, however, projects a much greater increase in rainfall than CMIP5 throughout the Twenty-First Century in autumn and winter. By the end of the century, CMIP6 models show a statistically significant increase in rainfall and statistically significant decrease in snowfall in autumn across most of the Arctic relative to CMIP5. Significant increases in rainfall and decreases in snowfall across the Atlantic side of the Arctic and the Bering sea are also found in spring and winter. Differences in precipitation between the CMIP experiments could be the result of Arctic sea ice loss which has been found to be greater in CMIP6 models than CMIP5 or potential changes in poleward heat and moisture transports. These results highlight that, in line with previous CMIPs, rainfall will dominate future Arctic climate but in a potentially greater way than previously found which will have significant consequences on the entire Arctic ecosystem.