29 Jan 2021

29 Jan 2021

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

Antecedent control on active ice sheet retreat revealed by seafloor geomorphology, offshore Windmill Islands, Antarctica

Alexandra L. Post1, Emrys Phillips2, Christopher J. Carson1, and Jodie Smith1 Alexandra L. Post et al.
  • 1Geoscience Australia, GPO Box 378, Canberra, ACT 2601, Australia
  • 2British Geological Survey, The Lyell Centre, Research Avenue South, Edinburgh EH14 4AP, UK

Abstract. Understanding past retreat of Antarctic ice margins provides valuable insight for predicting how ice sheets may respond to future environmental change. This study, based on high resolution multibeam bathymetry from the nearshore region of the Windmill Islands, East Antarctica, reveals a style of retreat that has been rarely observed on the Antarctic margin. A suite of seafloor features record the final retreat stages of a relatively thin, and increasingly fractured tidewater glacier confined within narrow troughs and embayments, forming a suite of features more typical of warm-based ice, but occurring here in a region of cold-based ice with limited surface meltwater production. The pattern of moraines and crevasse squeeze ridges, reveals strong topographic and substrate control on the nature of ice sheet retreat. Topographic control is indicated by fine-scale variability in the orientation and distribution of glacial landforms, which show that the seabed topography influenced the shape of the ice margin, caused deflection of ice flow and led to the separation of flow downstream from topographic highs. The availability of water saturated marine sediments within the troughs and depressions also had a profound effect on the landform record, facilitating the construction of moraines and crevasse squeeze ridges within topographic lows, corresponding to areas of modern sediment accumulation. Surrounding areas of crystalline bedrock, by contrast, acted as sticky spots and lack a well-developed landform record. This seafloor glacial record emphasises the importance of understanding the bed topography and substrate when predicting the nature of ice margin retreat and provides new perspectives for understanding the stability of the East Antarctic margin.

Alexandra L. Post et al.

Status: open (extended)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on tc-2021-8', Anonymous Referee #1, 03 Mar 2021 reply

Alexandra L. Post et al.

Data sets

Casey Station Multibeam Surveys 2013-2015 M. Spinoccia

Alexandra L. Post et al.


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Short summary
The seafloor is one of the best places to look for evidence of past response of the Antarctic ice sheet to environmental change. This work uses extremely high resolution bathymetry to interpret features imprinted onto the seafloor during last retreat of the Law Dome ice sheet. Seafloor features reveal the influence of pre-existing conditions, such as the underlying topography and the existence of sediment or bedrock, providing context to understand how ice sheets may respond to future change.