Abstract
Abstract. Here we present the results of a comprehensive glaciological investigation of Union Glacier (79°46' S/83°24' W) in the West Antarctic Ice Sheet (WAIS), a major outlet glacier within the Ellsworth Mountains. Union Glacier flows into the Ronne Ice Shelf, where recent models have indicated the potential for significant grounding line zone (GLZ) migrations in response to changing climate and ocean conditions. To elaborate a glaciological base line that can help to evaluate the potential impact of this GLZ change scenario, we installed an array of stakes on Union Glacier in 2007. The stake network has been surveyed repeatedly for elevation, velocity, and net surface mass balance. The region of the stake measurements is in near-equilibrium, and ice speeds are 10 to 33 m a−1. Ground-penetrating radars (GPR) have been used to map the subglacial topography, internal structure, and crevasse frequency and depth along surveyed tracks in the stake site area. The bedrock in this area has a minimum elevation of −858 m a.s.l., significantly deeper than shown by BEDMAP2 data. However, between this deeper area and the local GLZ, there is a threshold where the subglacial topography shows a maximum altitude of 190 m. This subglacial condition implies that an upstream migration of the GLZ will not have strong effects on Union Glacier until it passes beyond this shallow ice pinning point.
Highlights
WAIS, the West Antarctic Ice Sheet (Fig. 1), has been considered potentially unstable because its bedrock is located well below sea level (Bamber et al, 2009) and its total disintegration could contribute up to 4.3 m (Fretwell et al, 2013) to global sea-level rise
The main aim of this paper is to present recent glaciological results obtained at Union Glacier and nearby areas that provide a base line for possible ice dynamic responses to ongoing and modelled future changes of Ronne Ice Shelf (RnIS)
The meteorological data collected at Union Glacier between 2008 and 2013 contain several gaps and invalid records, but in general provide a good idea of the local conditions, which are especially useful for landing operations
Summary
WAIS, the West Antarctic Ice Sheet (Fig. 1), has been considered potentially unstable because its bedrock is located well below sea level (Bamber et al, 2009) and its total disintegration could contribute up to 4.3 m (Fretwell et al, 2013) to global sea-level rise. The topography underneath WAIS is inversed (ice is deeper upstream) and steeper than in the present grounding line zones (GLZ) (Ross et al, 2012) This topographic condition, in the context of ongoing global changes, especially oceanic warming in areas of the Southern Ocean, is leading to GLZ upstream migration, as observed for example in the Amundsen Sea Embayment area (ASEA) glaciers like Pine Island (PIG) and Thwaites (Rignot et al, 2002). This migration process in the context of inversed subglacial topographies has an impact on glacier dynamics, since bottom melting at the GLZ is higher in deeper waters, provoking higher ice fluxes, ice thinning and, in general, a more negative mass balance (Rignot and Jacobs, 2002). The intrusion of warmer waters will certainly increase the basal melt rate of the ice shelf, and possibly lead
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