Preprints
https://doi.org/10.5194/tc-2021-214
https://doi.org/10.5194/tc-2021-214
22 Jul 2021
 | 22 Jul 2021
Status: this preprint was under review for the journal TC but the revision was not accepted.

Changes in Supraglacial Lakes on George VI Ice Shelf, Antarctic Peninsula: 1973–2020

Thomas James Barnes, Amber Alexandra Leeson, Malcolm McMillan, Vincent Verjans, Jeremy Carter, and Christoph Kittel

Abstract. High densities of supraglacial lakes have been associated with ice shelf instability and collapse. 2020 was a record melt year on George VI ice shelf with ~12 % of its northernmost portion being covered by lakes. We use 208 Sentinel-2 and Landsat-1-8 satellite images from the past 47 years, together with climate data and firn modelling, to assess the long-term presence of lakes on George VI, thus placing 2020 within a historical context. We find that the ~12 % lake coverage observed in 2020 is not unprecedented and similar to previous high lake years; events of similar magnitude occurred at least five times previously. Secondly, we find lake coverage is controlled by a combination of melting, accumulation, firn air content and firn build-up strong melting alone does not entail high lake coverage. Instead, while melting contributes positively to lake formation, we find accumulation to act as a limiting factor on the formation of lakes in response to melt, introducing new frozen material to the surface, thus cooling and storing meltwater. We find accumulation’s ability to limit melt to be further enhanced by its build-up, increasing available firn air content, and thus meltwater storage capacity. Our findings are supported by comparative analysis, showing years such as 1989 to have 55 % less melt, but similar lake coverage to 2020. Finally, we find that climate projections suggest future temperature increases, but steady snowfall in this region. Thus, in future there will be a greater propensity for higher lake densities on North George VI ice shelf, and associated risk of instability.

Thomas James Barnes, Amber Alexandra Leeson, Malcolm McMillan, Vincent Verjans, Jeremy Carter, and Christoph Kittel

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on tc-2021-214', Anonymous Referee #1, 06 Aug 2021
    • AC1: 'Reply on RC1', Thomas Barnes, 23 Sep 2021
  • RC2: 'Comment on tc-2021-214', Anonymous Referee #2, 22 Aug 2021
    • AC2: 'Reply on RC2', Thomas Barnes, 23 Sep 2021
  • AC3: 'Comment on tc-2021-214', Thomas Barnes, 18 Mar 2022

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on tc-2021-214', Anonymous Referee #1, 06 Aug 2021
    • AC1: 'Reply on RC1', Thomas Barnes, 23 Sep 2021
  • RC2: 'Comment on tc-2021-214', Anonymous Referee #2, 22 Aug 2021
    • AC2: 'Reply on RC2', Thomas Barnes, 23 Sep 2021
  • AC3: 'Comment on tc-2021-214', Thomas Barnes, 18 Mar 2022
Thomas James Barnes, Amber Alexandra Leeson, Malcolm McMillan, Vincent Verjans, Jeremy Carter, and Christoph Kittel
Thomas James Barnes, Amber Alexandra Leeson, Malcolm McMillan, Vincent Verjans, Jeremy Carter, and Christoph Kittel

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Short summary
We find that the area covered by lakes on George VI ice shelf in 2020 is similar to that seen in other years such as 1989. However, the climate conditions are much more in favour of lakes forming. We find that it is likely that snowfall, and the build up of a surface snow layer limits the development of lakes on the surface of George VI ice shelf in 2020. We also find that in future, snowfall is predicted to decrease, and therefore this limiting effect may be reduced in future.