Strong summer atmospheric rivers induce Greenland Ice Sheet melt through spatially varying modification of the surface energy balance

Authors: Kyle Mattingly*, University of Georgia, Thomas Mote, University of Georgia, Xavier Fettweis, University of Liège
Topics: Cryosphere, Climatology and Meteorology, Polar Regions
Keywords: Greenland Ice Sheet, atmospheric rivers, synoptic climatology
Session Type: Guided Poster
Day: 4/4/2019
Start / End Time: 1:10 PM / 2:50 PM
Room: Roosevelt 3.5, Marriott, Exhibition Level
Presentation File: No File Uploaded

The Greenland Ice Sheet (GrIS) has lost mass at an accelerating pace since the turn of the 21st century and has become the largest contributor to global mean sea level rise. Several major GrIS melt events in recent years occurred during intense moisture transport over Greenland by atmospheric rivers (ARs), and recent research has shown that melt anomalies are greatest when strong ARs impact western Greenland during summer. In this study, we elucidate the physical mechanisms through which ARs cause GrIS melt by examining AR-induced changes to the surface energy balance. We compile an AR catalog from MERRA-2 reanalysis and classify strong ARs (AR90+) as those whose water vapor transport exceeds the 90th climatological percentile. We then examine surface energy balance anomalies during ARs—and the atmospheric processes driving energy fluxes—using the Modèle Atmosphérique Régional (MAR) regional climate model, in situ observations, and ERA5 reanalysis data. In the area surrounding AR90+ landfall, we find that strong positive sensible and latent heat flux outweigh radiative fluxes in the low-elevation ablation zone and generate intense melting. At higher elevations, positive longwave and latent heat flux anomalies exceed negative shortwave and sensible heat flux anomalies and cause more moderate melt. Enhanced cloud cover produces these changes to radiative fluxes, while turbulent fluxes are driven by strong barrier jet winds over western Greenland. AR90+ events affecting northwest Greenland trigger melt in the lower elevations of the eastern GrIS through distinct processes, as downsloping flow causes reduced cloud cover and strong sensible heat fluxes.

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