The Influence of Local and Remote Moisture Sources on Arctic Precipitation

To meet the increasing atmospheric demand in a warmer world, the Arctic is projected to become more moist following the Clausius-Clapeyron relation. Furthermore, future projections show that Arctic mean precipitation increases more than twice as much as global mean precipitation per degree of warming. Increases in Arctic precipitation are linked to changes in its moisture sources, local surface evaporation and remote moisture transport from lower latitudes. Here, we directly probe the Arctic system to individually assess these drivers of Arctic precipitation change. We run four 50-year atmosphere-only CESM2 simulations to quantify the separate influences of local surface evaporation and remote moisture transport on Arctic precipitation change. To accomplish this separation, we prescribe sea surface temperatures (SST) and sea ice extent (SIE). The atmosphere-only simulations reproduce the fully coupled precipitation response, suggesting that total precipitation is controlled by surface evaporation changes driven by changes in SST and SIE. We find that local evaporation dominates fall and winter Arctic precipitation change, while remote moisture transport dominates during the rest of the year. Similarly, the local simulation dominates fall and winter near-surface Arctic temperature response, while the remote simulation fully explains the temperature aloft.