Preprints
https://doi.org/10.5194/tc-2021-360
https://doi.org/10.5194/tc-2021-360

  21 Dec 2021

21 Dec 2021

Review status: this preprint is currently under review for the journal TC.

Review article: Existing and potential evidence for Holocene grounding-line retreat and readvance in Antarctica

Joanne S. Johnson1, Ryan A. Venturelli2, Greg Balco3, Claire S. Allen1, Scott Braddock4, Seth Campbell4, Brent M. Goehring2, Brenda L. Hall4, Peter D. Neff5, Keir A. Nichols6, Dylan H. Rood6, Elizabeth R. Thomas1, and John Woodward7 Joanne S. Johnson et al.
  • 1British Antarctic Survey, High Cross, Madingley Road, Cambridge, CB3 0ET, UK
  • 2Department of Earth & Environmental Sciences, Tulane University, New Orleans, LA 70118, USA
  • 3Berkeley Geochronology Center, 2455 Ridge Road, Berkeley, CA 94709, USA
  • 4School of Earth and Climate Sciences and the Climate Change Institute, University of Maine, Orono, ME 04469 USA
  • 5Department of Soil, Water, and Climate, University of Minnesota, Saint Paul, MN 55108, USA
  • 6Department of Earth Science & Engineering, Imperial College London, London SW7 2AZ, UK
  • 7Department of Geography and Environmental Sciences, Northumbria University, Newcastle-upon-Tyne, NE1 8ST, UK

Abstract. Widespread existing geological records from above the modern ice-sheet surface and outboard of the current ice margin show that the Antarctic Ice Sheet (AIS) was much more extensive at the Last Glacial Maximum (~20 ka) than at present. However, whether it was ever smaller than present during the last few millennia, and (if so) by how much, is known only for a few locations because direct evidence lies within or beneath the ice sheet, which is challenging to access. Here, we describe how retreat and readvance (henceforth “readvance”) of AIS grounding lines during the Holocene could be detected and quantified using subglacial bedrock, subglacial sediments, marine sediment cores, relative sea-level (RSL) records, radar data, and ice cores. Of these, only subglacial bedrock and subglacial sediments can provide direct evidence for readvance. Marine archives are of limited utility because readvance commonly covers evidence of earlier retreat. Nevertheless, stratigraphic transitions documenting change in environment may provide support for direct evidence from subglacial records, as can the presence of transgressions in RSL records. With independent age control, past changes in ice structure and flow patterns revealed by radar can be used to infer ice volume changes commensurate with readvance. Since ice cores capture changes in surface mass balance, elevation, and changes in atmospheric and oceanic circulation that are known to drive grounding-line migration, they also have potential for identifying readvance. A multidisciplinary approach is likely to provide the strongest evidence for or against a smaller-than-present AIS in the Holocene.

Joanne S. Johnson et al.

Status: open (until 15 Feb 2022)

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Joanne S. Johnson et al.

Joanne S. Johnson et al.

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Short summary
Recent studies have suggested that some portions of the Antarctic Ice Sheet were less extensive than present in the last few thousand years. We discuss how past ice loss and regrowth during this time would leave its mark on geological and glaciological records and suggest ways in which future studies could detect such changes. Determining timing of ice loss and gain around Antarctica and conditions under which they occurred is critical for preparing for future climate warming-induced changes.