Preprints
https://doi.org/10.5194/tc-2022-82
https://doi.org/10.5194/tc-2022-82
 
05 May 2022
05 May 2022
Status: this preprint is currently under review for the journal TC.

New 10Be exposure ages improve Holocene ice sheet thinning history near the grounding line of Pope Glacier, Antarctica

Jonathan Richard Adams1,2, Joanne S. Johnson1, Stephen J. Roberts1, Philippa J. Mason2, Keir A. Nichols2, Ryan A. Venturelli3, Klaus Wilcken4, Greg Balco5, Brent Goehring3, Brenda Hall6, John Woodward7, and Dylan H. Rood2 Jonathan Richard Adams et al.
  • 1British Antarctic Survey, High Cross, Madingley Road, Cambridge CB3 0ET, UK
  • 2Department of Earth Science & Engineering, Imperial College London, London SW7 2AZ, UK
  • 3Department of Earth & Environmental Sciences, Tulane University, New Orleans, LA 70118, USA
  • 4Australia’s Nuclear Science and Technology Organisation (ANSTO), New Illawarra Road, Lucas Heights, NSW 2234, Locked Bag 2001, Kirrawee DC 2232, Australia
  • 5Berkeley Geochronology Center, 2455 Ridge Road, Berkeley, CA 94709, USA
  • 6School of Earth and Climate Sciences and the Climate Change Institute, University of Maine, Orono, ME 04469 USA
  • 7Department of Geography and Environmental Sciences, Northumbria University, Newcastle-upon-Tyne, NE1 8ST, UK

Abstract. Evidence for the timing and pace of past grounding line retreat of the Thwaites Glacier system in the Amundsen Sea embayment (ASE) of Antarctica provides constraints for models that are used to predict the future trajectory of the West Antarctic Ice Sheet (WAIS). Existing cosmogenic nuclide surface exposure ages suggest that Pope Glacier, a former tributary of Thwaites Glacier, experienced rapid thinning in the early to mid-Holocene. There are relatively few exposure ages from the lower ice-free sections of Mount Murphy (< 300 m asl) that are uncomplicated by either nuclide inheritance or scattering due to localised topographic complexities; this makes the trajectory for the latter stages of deglaciation uncertain. This paper presents 12 new 10Be exposure ages from erratic cobbles collected from the western flank of Mt Murphy, within 160 m of the modern ice surface and 1 km from the present grounding line. The ages comprise two tightly clustered populations with mean deglaciation ages of 7.1 ± 0.1 ka and 6.4 ± 0.1 ka (1SE). Linear regression analysis applied to the age-elevation array of all available exposure ages from Mt Murphy indicates that the median rate of thinning of Pope Glacier was 0.27 m yr-1 between 8.1–6.3 ka, occurring 1.5 times faster than previously thought. Furthermore, this analysis better constrains the uncertainty (95 % confidence interval) in the timing of deglaciation at the base of the Mt Murphy vertical profile (~80 m above the modern ice surface), shifting it to earlier in the Holocene (from 5.2 ± 0.7 ka to 6.3 ± 0.4 ka). Taken together, the results presented here suggest that early–mid Holocene thinning of Pope Glacier occurred over a shorter interval than previously assumed and permit a longer duration over which subsequent late Holocene rethickening could have occurred.

Jonathan Richard Adams et al.

Status: open (until 30 Jun 2022)

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Jonathan Richard Adams et al.

Jonathan Richard Adams et al.

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Short summary
Glaciers in West Antarctica are experiencing significant ice loss. Geological data provide historical context for ongoing ice loss in West Antarctica, including constraints on likely future ice sheet behaviour in response to climatic warming. We present evidence from rare isotopes measured in rocks collected from an outcrop next to Pope Glacier. These data suggest that Pope Glacier thinned faster and sooner after the last ice age than previously thought.