Surface elevation changes on land terminating sectors of West Greenland during recent decades

Abstract:

Regional and site-specific studies of Greenland Ice Sheet elevation change have focused on marine terminating outlets, where ice discharge to the ocean is a dominant control on thinning. Land terminating regions should be controlled by surface mass balance processes, and therefore offer a reference control to marine outlets. Yet, isolated assessments of these sectors have largely been neglected. Here we employ DEM analysis to investigate the multi-decadal elevation change over Western Greenland’s land terminating region at high spatial resolution. We used Aerial photograph-based AeroDEM for 1985, the Greenland Ice Mapping Project DEM (GIMP) for 2007, and ArcticDEM for 2013 and 2017 to quantify mass changes over the last 32 years. We find ice mass loss over the study area (7954 km²) during this time to be 956 Gt, amounting to a sea level rise of 2.64 mm. The mean elevation change rate was lowest during 1985-2007 (–0.06 m a^–1) and increased between 2007-2013 (–1.40 m a^–1). Thinning rates declined between 2013-2017 (–1.13 m a^–1), with many regions experiencing net thickening. Unsurprisingly, the primary control of elevation loss along the southwest margin is negative Surface Mass Balance (SMB) However, our results reveal spatial patterns in elevation change that align with ice flow and geometry. This indicates that dynamic processes influence ice sheet elevation over multi-annual time scales, which are likely to influence interpretations of mass change based on sparse data.