Recent ice dynamic and surface mass balance of Union Glacier in the West Antarctic Ice Sheet

摘要

Here we present the results of a comprehensive glaciological investigation ofUnion Glacier (79°46' S/83°24' W) in the WestAntarctic Ice Sheet (WAIS), a major outlet glacier within the EllsworthMountains. Union Glacier flows into the Ronne Ice Shelf, where recent modelshave indicated the potential for significant grounding line zone (GLZ)migrations in response to changing climate and ocean conditions. To elaboratea glaciological base line that can help to evaluate the potential impact ofthis GLZ change scenario, we installed an array of stakes on Union Glacier in2007. The stake network has been surveyed repeatedly for elevation, velocity,and net surface mass balance. The region of the stake measurements is innear-equilibrium, and ice speeds are 10 to 33 m a?1.Ground-penetrating radars (GPR) have been used to map thesubglacialtopography, internal structure, and crevasse frequency and depth alongsurveyed tracks in the stake site area. The bedrock in this area has aminimum elevation of ?858 m a.s.l., significantly deeper than shown byBEDMAP2 data. However, between this deeper area and the local GLZ, there is athreshold where the subglacial topography shows a maximum altitude of 190 m.This subglacial condition implies that an upstream migration of the GLZ willnot have strong effects on Union Glacier until it passes beyond this shallowice pinning point.