Climate Dependence of Arctic Precipitation Variability

Abstract

The increase in Arctic precipitation is expected to amplify more rapidly than the global mean in warming climates. However, the warming-induced changes in variability of Arctic precipitation, evaporation, and poleward moisture transport are currently largely unknown. This study compares the precipitation variability in quasi-equilibrium climates with different CO2 concentrations from a global climate model and studies the underlying mechanisms. Five quasi-equilibrium simulations of 400 years forced with a broad range of CO2 concentrations (0.25, 0.5, 1, 2, and 4 times the current global mean) using the EC-Earth model were analyzed. Poleward moisture transport variability is presumably responsible for Arctic precipitation variability in colder climates as the ocean in the Arctic basin is completely covered by sea ice. Arctic precipitation variability increases towards warmer climates primarily in summer, because of i) the strong increase in mean precipitation in winter due to enhanced evaporation (which exerts a comparatively small increase in variability), ii) the strong interaction between poleward moisture transport and evaporation in winter, and iii) the increasing relation between Arctic sea level pressure variability and precipitation variability in summer in warmer climates.