Are transition season melt events on the Greenland Ice Sheet driven by
Baffin Bay sea ice-atmosphere interactions?
Abstract
A number of insitu and passive microwave satellite sensors have observed
Arctic sea ice and Greenland Ice Sheet (GrIS) mass loss trends over
recent decades. Along with sea and land ice declines, above-freezing,
near-surface air temperatures are observed earlier in boreal spring and
later in autumn thus extending periods of melt beyond the core of summer
(JJA). Little is known about whether lengthening periods of open ocean
proximate to the ice sheet, for instance, demonstrably effect unseasonal
GrIS melt events. Here, a new Baffin Bay sea ice advance dataset is
utilized to determine dates of sea ice growth along Greenland’s west
coast for the 2011-2015 period. Preceding, multi-scale ocean-atmospheric
conditions, including at the Baffin-GrIS interface, are analyzed and
linked to unseasonal melt events observed at a series of on-ice
automatic weather stations (AWS) along the K-transect in southwest
Greenland. The local marine versus synoptic influence on the above and
below freezing surface air temperature events is assessed through
analyses involving AWS winds, pressure, and humidity observations. These
surface observations are further compared against Modele Atmospherique
Regional (MAR), Regional Atmospheric Climate Model (RACMO), and
ERA-Interim reanalysis fields to understand the airmass origins and
(thermo)dynamic drivers of the melt events. Results suggest that the
K-transect transition season melt events, primarily in the ablation
zone, are strongly affected by ridging atmospheric circulation patterns
that transport warm, moist air from lower latitude land-ocean areas
toward west Greenland. While local conduction of oceanic surface heat
appears to impact coastal air temperatures, consistent with previous
studies, marine air incursions from Baffin waters onto the ice sheet are
likely obstructed by barrier flows and the pressure gradient-driven
katabatic regime off of central Greenland.