Historical changes in Arctic moisture budget as simulated by CMIP6 individual forcing experiments

Abstract

The past changes in atmospheric moisture transport over the Arctic are evaluated using CMIP6 multi-model simulations. To examine possible influences of external forcings, CMIP6 multi-model simulations performed under natural-plus-anthropogenic (ALL), greenhouse gas (GHG), natural (NAT), and aerosol (AER) forcings are compared. Results indicate that Arctic precipitation and evaporation increase in ALL and GHG while they decrease in AER. In ALL and GHG simulations, Arctic precipitation increases in summer majorly due to enhanced poleward moisture transport whereas Arctic moistening during winter is affected more by increased surface evaporation over sea-ice retreat areas. In AER, Arctic precipitation tends to decrease due to reduced evaporation over sea-ice advance areas. The response of meridional moisture flux (MMF) is largely determined by variations in transient eddies (TE) with distinct seasonal contributions from different regions. In ALL, the contribution of the Pacific sector is dominant during summer, but the Atlantic sector becomes a main source during autumn. The summer increase of TE in ALL is greater than that of GHG, which is found to be partly due to the stronger contribution of the Atlantic sector in ALL.