Antarctic surface and subsurface melting dynamics: Enhanced perspectives from radar scatterometer data

Surface and subsurface melting across the Antarctic Ice Sheet are important processes with implications in numerous physical, climatological, and glaciological contexts. These include regional implications for ice shelf stability, mass balance, and glacier dynamics, in addition to modulating near-surface physical properties, energy fluxes, and glaciochemistry over wide areas. Here, we employ satellite-derived radar scatterometer measurements of melting from the QuikSCAT, encompassing a near-daily and continent-wide time series spanning 10 melt seasons from 1999 to 2009. These remotely sensed data are explored in concert with in situ meteorological records to validate a threshold-based melt detection method. Our results reveal greater spatiotemporal melt detection relative to previous studies, which we partially attribute to increased sensitivity to subsurface melting. Significant correlations between radar backscatter reductions during melting and in situ positive degree days supports the use of QuikSCAT for determining the interannual variability of melt intensity, or the relative liquid water production during melting. On average, the Antarctic Peninsula accounts for only one-fifth the total melting area but over half of the total Antarctic melt intensity. Broad spatiotemporal agreement exists between melt duration and intensity, but regional and localized distinctions occur where the intensity metric provides the most additional benefit. Teleconnections exist between continental melt intensity and the Southern Annular Mode and the Southern Oscillation Index, and anomalously extensive melting across the Ross Ice Shelf region is thought to be associated with El Niño conditions. By providing new insights into melting dynamics, this research enhances the understanding of the Antarctic cryosphere and may aid in predictions of future change under enhanced warming.