Using in situ 14C to unravel complex exposure histories along the David Glacier, Antarctica
Dr Jamey Stutz1, Dr. Reka Fülop2, Dr. Kevin Norton3, Dr. Andrew Mackintosh4, Dr. Ross Whitmore4, Dr. Bin Yang2, Dr. Andrew Smith2
1Antarctic Research Centre, Te Herenga Waka – Victoria University Of Wellington, , New Zealand, 2Australian Nuclear Science and Technology Organisation, Sydney, Australia, 3School of Geography, Environment and Earth Sciences, Wellington, New Zealand, 4School of Earth, Environment and Atmosphere, Melbourne, Australia
Understanding the past Antarctic Ice Sheet (AIS) is critical to forecast the impacts of future of the AIS and its contribution to sea level rise. Ice sheet models constrained by geological data provide improved confidence in future projections. Both marine and terrestrial geologic data are required for a robust reconstruction of both the extent and thickness of the AIS. On land, cosmogenic nuclides have transformed the ability to constrain reconstructions of the past AIS through time. High-resolution, low-inheritance chronologies focused on large outlet glaciers provide enhanced understanding on the timing, rate and potential mechanisms driving past ice sheet change. Using the ‘glacial dip stick’ approach at each site, we sample glacial debris and bedrock from the local peak down to the modern ice surface. While field sampling strategies and analytical capability continues to improve, ‘complex’ exposure histories remain a common occurrence in practice. Inheritance, or a signal of cumulative exposure, can arise due to burial by cold-based, non-erosive nature of the AIS. At Mt. Kring along the upper David Glacier, previous studies show a distinct mid-Holocene signal of glacier thinning as well as at least two populations of apparent older glacial thinning events. Here, we use 14C measurements on samples suspected of having an inherited signal. We show that samples with >30 ka 10Be exposure ages indeed carry a mid-Holocene 14C exposure age and improve the existing thinning history. This multi-nuclide comparison approach provides a preliminary data set to bolster previous and emerging studies where complex exposure histories occur around Antarctica.
Jamey is a glacial geologist, primarily working in Antarctica. He uses cosmogenic nuclides extracted from glacial debris to reconstruct past glacier thickness. Jamey comes from The Ohio State University where he completed his masters before coming to New Zealand to complete his PhD and continues working at the Antarctic Research Centre.