Atmospheric Processes Influencing Surface Temperature over Greenland from the MERRA-2 Reanalysis

Abstract:

The Greenland Ice Sheet (GIS) has been undergoing rapid warming and mass loss and experienced
the seasonal melting record in the summer of 2012, punctuated by a melt event on July 11
unprecedented in the satellite record. Many studies have shown that the proximal cause of the
melt event was the advection of warm air related to an anomalous stationary wave pattern.
Reanalysis fields from MERRA-2 are used here to examine the mechanisms by which the warm
anomaly in the atmosphere resulted in the surface temperature anomaly by contrasting the
summers of 2012 and 2013. It is shown that although the cloud cover anomaly in 2012 was
small, the increased downwelling terrestrial radiation due to the warmer cloud temperatures
was responsible for the warm surface temperatures and the melting. Observational confirmation
of all the aspects of the atmospheric and surface budgets was not possible, but the conclusions
based on MERRA-2 reanalysis fields were supported with in situ observations of radiative fluxes
where available.