Abstract

<strong class="journal-contentHeaderColor">Abstract.</strong> The discovery of Antarctica's deepest subglacial trough beneath the Denman Glacier, combined with high rates of basal melt at the grounding line, has caused significant concern over its vulnerability to retreat. Recent attention has therefore been focusing on understanding the controls driving Denman Glacier's dynamic evolution. Here we consider the Shackleton system, comprised of the Shackleton Ice Shelf, Denman Glacier, and the adjacent Scott, Northcliff, Roscoe and Apfel glaciers, about which almost nothing is known. We widen the context of previously observed dynamic changes in the Denman Glacier to the wider region of the Shackleton system, with a multi-decadal time frame and an improved biannual temporal frequency of observations in the last 7 years (2015–2022). We integrate new satellite observations of ice structure and airborne radar data with changes in ice front position and ice flow velocities to investigate changes in the system. Over the 60-year period of observation we find significant rift propagation on the Shackleton Ice Shelf and Scott Glacier and notable structural changes in the floating shear margins between the ice shelf and the outlet glaciers, as well as features indicative of ice with elevated salt concentration and brine infiltration in regions of the system. Over the period 2017–2022 we observe a significant increase in ice flow speed (up to 50 %) on the floating part of Scott Glacier, coincident with small-scale calving and rift propagation close to the ice front. We do not observe any seasonal variation or significant change in ice flow speed across the rest of the Shackleton system. Given the potential vulnerability of the system to accelerating retreat into the overdeepened, potentially sediment-filled bedrock trough, an improved understanding of the glaciological, oceanographic and geological conditions in the Shackleton system are required to improve the certainty of numerical model predictions, and we identify a number of priorities for future research. With access to these remote coastal regions a major challenge, coordinated internationally collaborative efforts are required to quantify how much the Shackleton region is likely to contribute to sea level rise in the coming centuries.

Highlights

  • The health of the West Antarctic Ice Sheet (WAIS) has attracted much scientific scrutiny in recent decades but there has been less focus on the East Antarctic Ice Sheet (EAIS) where historically the consensus was one of relative stability (Silvano et al, 2016)

  • With access to these remote coastal regions a major challenge, coordinated internationally collaborative efforts are required to quantify how much the Queen Mary and Knox coastal region is likely contribute to sea level rise in the coming centuries

  • 5 Conclusions 340 We conclude that over the 60-year period of observation, the Queen Mary and Knox coasts do not appear to have changed significantly and higher frequency observations have not revealed any significant annual or sub-annual variations in ice flow

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Summary

Introduction

The health of the West Antarctic Ice Sheet (WAIS) has attracted much scientific scrutiny in recent decades but there has been less focus on the East Antarctic Ice Sheet (EAIS) where historically the consensus was one of relative stability (Silvano et al, 2016). 50 The Shackleton system flows from a major drainage basin at the EAIS margin, located at the intersection of the Queen Mary and Knox coasts (Fig. 1a) It is supplied by several outlet glaciers, including Denman, Scott, Northcliffe, Roscoe and Apfel. The floating component of the system is comprised of the Shackleton Ice Shelf together with the distinctive floating tongues of Denman, Scott and Roscoe, and an area of fast ice to the west of the Denman floating tongue (Fig. 1b) It is one of the 55 largest drainage basins in East Antarctica, located close to the margin of the continental shelf, and is thought connect to the western portion of the Aurora subglacial basin via the Knox Basin (Fig. 1a). The Denman Glacier alone is thought to hold an equivalent of 1.5 m sea level rise (Rignot et al, 2019)

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