Abstract
Abstract. One consequence of recent Arctic warming is an increased occurrence and longer seasonality of above-freezing air temperature episodes. There is significant disagreement in the literature concerning potential physical connectivity between high-latitude open water duration proximate to the Greenland Ice Sheet (GrIS) and late-season (i.e., end-of-summer and autumn) GrIS melt events. Here, a new date of sea ice advance (DOA) product is used to determine the occurrence of Baffin Bay sea ice growth along Greenland's west coast for the 2011–2015 period. Over the 2-month period preceding the DOA, northwest Atlantic Ocean and atmospheric conditions are analyzed and linked to late-season melt events observed at a series of on-ice automatic weather stations (AWSs) along the K-transect in southwestern Greenland. Surrounding ice sheet, tundra, and coastal winds from the Modèle Atmosphérique Régional (MAR) and Regional Atmospheric Climate Model (RACMO) provide high-resolution spatial context to AWS observations and are analyzed along with ERA-Interim reanalysis fields to understand the meso-to-synoptic-scale (thermo)dynamic drivers of the melt events. Results suggest that late-season melt events, which primarily occur in the ablation area, are strongly affected by ridging atmospheric circulation patterns that transport warm, moist air from the subpolar North Atlantic toward west Greenland. Increasing concentrations of North Atlantic water vapor are shown to be necessary to produce melt conditions as autumn progresses. While thermal conduction and advection off south Baffin Bay open waters impact coastal air temperatures, local marine air incursions are obstructed by barrier flows and persistent katabatic winds along the western GrIS margin.
Highlights
Substantial decline in Arctic sea ice extent and mass loss from the Greenland Ice Sheet (GrIS) have been observed for the last four decades (e.g., Serreze and Stroeve, 2015; Bamber et al, 2018)
A significant break in the 2 % series is highlighted by a drastic increase in variability from 1979–1999 (σ = 21.17) to 2000– 2015 (σ = 44.25) that is present in the annual discharge records from the nearby Watson River and Tasersiaq ice sheet catchments (Ahlstrøm et al, 2017; van As et al, 2018)
Based on our 2011–2015 analyses bridging the end-ofsummer/early autumn melt to the date of first-year Baffin Bay sea ice advance, we do not find evidence to support the hypothesis that local open water, resultant turbulent heating, and onshore winds have a pronounced impact on inland ice melt events
Summary
Substantial decline in Arctic sea ice extent and mass loss from the Greenland Ice Sheet (GrIS) have been observed for the last four decades (e.g., Serreze and Stroeve, 2015; Bamber et al, 2018). Ballinger et al.: Drivers of K-transect late-season melt events ocean waters west of Greenland since at least the early 1990s is linked to accelerated submarine melt and outlet glacier retreat (Holland et al, 2008; Straneo and Heimbach, 2013) concurrent with more frequent summertime air temperature extremes along the coast (Hanna et al, 2012; Mernild et al, 2014). These findings raise the question of whether Baffin local ocean conditions are of importance in governing the spatial extent and temporal variations in western GrIS melt
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