Affiliation:
1. Antarctic Research Centre Wellington New Zealand
2. School of Geography, Earth and Environmental Sciences Te‐Herenga Waka Victoria University of Wellington Wellington New Zealand
3. ANSTO Lucas Heights NSW Australia
4. GNS Science Lower Hutt New Zealand
5. Indiana University‐Purdue University Indianapolis Indianapolis Indiana USA
Abstract
AbstractGeomorphological records of past ice sheet change offer the opportunity to examine their centennial‐scale response to changing boundary conditions, which are not adequately captured in the satellite record. Here, we present the first reconstruction of ice surface lowering at Byrd Glacier, the largest outlet glacier of the Transantarctic Mountains. Using surface exposure ages from glacial erratic cobbles collected in two vertical transects along the Lonewolf Nunataks, we find the initial emergence of this set of nunataks occurred at ~15 ka, with a rapid pulse of thinning at ~8 ka. We compare our glacier thinning profiles with modelled ice sheet thickness and grounding line histories from two model ensembles to identify key processes responsible for ice sheet change. All model runs from the two ensembles predict grounding line retreat and inland thinning to occur in one rapid step from Last Glacial Maximum to present, in line with marine geology records, our exposure age data and derived glacier thinning rates. Experiments best matching the glacial thickness constraints, reconstructed from the surface exposure data, have faster basal sliding (i.e., promote greater sliding rates resulting in thinner ice). However, experiments best matching the timing and rapid rate of ice thinning derived from the same surface exposure data have higher basal friction. This apparent change in the modelled basal sliding regime, from when the ice surface is at maximum thickness, to the rapid thinning at ~8 ka, occurs as the grounding line retreats towards the Byrd Glacier and Ross Ice Shelf forms during the Holocene. This past context has implications for the stability of the modern grounding line of Byrd Glacier, which is characterised by high basal melt rates at the terminus—a process that has the potential to propagate glacier thinning far inland, impacting the overall (in)stability of the Byrd Glacier and Ross Ice Shelf.
Funder
Antarctic Climate and Ecosystems Cooperative Research Centre
Australian Institute of Nuclear Science and Engineering
Ministry for Business Innovation and Employment
Subject
Earth and Planetary Sciences (miscellaneous),Earth-Surface Processes,Geography, Planning and Development