Impacts of Atmospheric Moisture Transport on Greenland Ice Sheet Melt and Energy Balance

The Greenland Ice Sheet (GrIS) has been losing mass in recent decades, with an acceleration in mass loss since 2000. This ice mass loss contributes directly to sea level rise and alters fluxes of mass and energy through the global ocean-atmosphere-cryosphere system. Several episodes of widespread GrIS melt in recent years have coincided with intense poleward moisture transport by “atmospheric rivers” (ARs), suggesting that these events act as poleward energy fluxes that play an important role in high-latitude warming. ARs may affect the GrIS energy budget through the greenhouse effect of water vapor, the release of latent heat by condensation (both locally and upstream within poleward-moving air masses), and the radiative effects of clouds. These impacts of ARs on the GrIS are important to understand because both theoretical and model-based studies predict that atmospheric moisture transport to the Northern Hemisphere high latitudes will increase in a warming climate.

Previous research on the role of ARs in Arctic climate has either consisted of case studies of a few moisture transport events affecting the GrIS or has examined the typical effects of poleward moisture flux on Arctic sea ice. This study provides the first long-term analysis of atmospheric moisture transport affecting the GrIS and its effects on ice sheet melt and energy balance. ARs are identified using a conventional feature-based “threshold” method applied to fields of integrated vapor transport (IVT) from various reanalysis datasets (ERA-Interim, MERRA, MERRA-2, and CFSR), and trends in these AR features are compared to trends in synoptic moisture transport patterns identified using a self-organizing map (SOM) classification. The effects of atmospheric moisture transport on GrIS melt and the regional energy budget are then analyzed using reanalysis data as well as MEaSUREs daily Greenland surface melt data from the National Snow and Ice Data Center, the Modèle Atmosphérique Régional (MAR) regional climate model, the NASA/GEWEX Surface Radiation Budget dataset, and various satellite-derived cloud products. Particular attention is focused on the changes in cloud properties and downwelling longwave radiation forced by poleward moisture transport events, as previous studies suggest that these processes play a key role in both ice sheet and sea ice melt.