Preprints
https://doi.org/10.5194/egusphere-2024-1452
https://doi.org/10.5194/egusphere-2024-1452
12 Jun 2024
 | 12 Jun 2024
Status: this preprint is open for discussion.

Detecting Holocene retreat and readvance in the Amundsen Sea sector of Antarctica: assessing the suitability of sites near Pine Island Glacier for subglacial bedrock drilling

Joanne S. Johnson, John Woodward, Ian Nesbitt, Kate Winter, Seth Campbell, Keir A. Nichols, Ryan A. Venturelli, Scott Braddock, Brent M. Goehring, Brenda Hall, Dylan H. Rood, and Greg Balco

Abstract. Unambiguous identification of past episodes of ice sheet thinning below the modern surface and grounding line retreat inboard of present requires recovery and exposure dating of subglacial bedrock. Such efforts are needed to understand the significance and potential future reversibility of ongoing and projected change in Antarctica. Here we evaluate the suitability for subglacial bedrock recovery drilling of sites in the Hudson Mountains, in the Amundsen Sea sector of West Antarctica. We use an ice sheet model and field data − geological observations, glaciological observations and bedrock samples from nunataks, and ground-penetrating radar from subglacial ridges − to rate each site against four key criteria: i) presence of ridges extending below the ice sheet, ii) likelihood of increased exposure of those ridges if the grounding line was inboard of present, iii) suitability of bedrock for drilling and geochemical analysis, and iv) accessibility for aircraft and drilling operations. Our results demonstrate that although no site in the Hudson Mountains is perfect for this study when assessed against all criteria, Winkie Nunatak (74.86° S / 99.77° W) is suitable. The accessibility, N-S orientation and basaltic bedrock lithology of its southernmost ridge make the nunatak a feasible site both for drilling and subsequent cosmogenic nuclide analysis. Furthermore, it is strewn with erratic cobbles at all elevations, providing constraints on the earlier Holocene deglacial history and time at which the ice sheet surface reached its present elevation. Such information is necessary for determining the maximum duration over which any Holocene grounding line readvance could have occurred.

Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this preprint. The responsibility to include appropriate place names lies with the authors.
Joanne S. Johnson, John Woodward, Ian Nesbitt, Kate Winter, Seth Campbell, Keir A. Nichols, Ryan A. Venturelli, Scott Braddock, Brent M. Goehring, Brenda Hall, Dylan H. Rood, and Greg Balco

Status: open (until 02 Aug 2024)

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  • RC1: 'Comment on egusphere-2024-1452', Jonathan Harbor, 15 Jul 2024 reply
Joanne S. Johnson, John Woodward, Ian Nesbitt, Kate Winter, Seth Campbell, Keir A. Nichols, Ryan A. Venturelli, Scott Braddock, Brent M. Goehring, Brenda Hall, Dylan H. Rood, and Greg Balco
Joanne S. Johnson, John Woodward, Ian Nesbitt, Kate Winter, Seth Campbell, Keir A. Nichols, Ryan A. Venturelli, Scott Braddock, Brent M. Goehring, Brenda Hall, Dylan H. Rood, and Greg Balco

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Short summary
Determining where and when the Antarctic ice sheet was smaller than present requires recovery and exposure dating of subglacial bedrock. Here we use ice sheet model outputs and field data (geological and glaciological observations, bedrock samples and ground-penetrating radar from subglacial ridges) to assess the suitability for drilling of sites in the Hudson Mountains, West Antarctica. We find that no sites are perfect, but two are feasible, with the most suitable being Winkie Nunatak.