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

• Main Authors: Barnes, Thomas James, Leeson, Amber Alexandra, McMillan, Malcolm, Verjans, Vincent, Carter, Jeremy, Kittel, Christoph
• Format: Text
• Language: English
• Published: 2021
• Subjects: Antarctic; Antarctic Peninsula; George VI Ice Shelf; High Lake; Antarc*; Ice Shelf
• Online Access: https://doi.org/10.5194/tc-2021-214; https://tc.copernicus.org/preprints/tc-2021-214/

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.