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Evaporative moisture sources contributing to atmospheric river events in western Greenland

Authors: Kyle Mattingly*, Rutgers University, Thomas Mote, University of Georgia
Topics: Climatology and Meteorology, Cryosphere, Polar Regions
Keywords: Greenland Ice Sheet, atmospheric rivers, moisture sources
Session Type: Paper
Day: 4/8/2020
Start / End Time: 9:35 AM / 10:50 AM
Room: Virtual Track 2
Presentation File: No File Uploaded

Greenland Ice Sheet (GrIS) melt is partially controlled by variability in the large-scale atmospheric circulation through its influence on the surface energy balance. Episodes of synoptic-scale water vapor transport in narrow plumes called atmospheric rivers (ARs) have been shown to force GrIS melt through modification of radiative and turbulent energy fluxes. In this study, the dynamical processes by which ARs link distant regions within the global hydrological cycle are investigated through analyses of the evaporative water vapor source regions for ARs impacting western Greenland. Conditions preceding ARs are first examined from a Eulerian perspective by comparing reanalysis evaporation fields and related variables during the 10 days prior to AR landfall to AR-free conditions. Moisture uptake by air parcels arriving over western Greenland is then analyzed from a Lagrangian perspective by tracking humidity changes along modelled parcel trajectories.

Results show that evaporative sources of water vapor reaching western Greenland shift equatorward during ARs, with enhanced moisture uptake occurring over a broad swath of the Atlantic Ocean during winter and summer, and parts of eastern North America during summer. Although air parcels gain water vapor from areas of anomalous evaporation identified by the Eulerian analysis, moisture uptake also occurs over areas of below-normal evaporation south of Greenland, likely due to convergence within the warm conveyer belts of extratropical cyclones. Thus ARs affecting western Greenland draw moisture from a mixture of distant, low-latitude sources and more proximate areas of the subpolar North Atlantic Ocean that contribute water vapor as air parcels approach Greenland.

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