32-year record-high surface melt in 2019/2020 on north George VI Ice Shelf, Antarctic Peninsula

Abstract

Abstract. In the 2019/2020 austral summer, the surface melt duration and extent on the northern George VI Ice Shelf (GVIIS) was exceptional compared to the 31 previous summers of dramatically lower melt. This finding is based on analysis of near-continuous 41-year satellite microwave radiometer (and scatterometer) data, which are sensitive to meltwater on the ice-shelf surface and in the near-surface snow. Using optical satellite imagery from Landsat 8 (since 2013) and Sentinel-2 (since 2017), record volumes of surface meltwater ponding are also observed on north GVIIS in 2019/2020, with 23 % of the surface area covered by 0.62 km3 of meltwater on January 19. These exceptional melt and surface ponding conditions in 2019/2020 were driven by sustained air temperatures ≥ 0 °C for anomalously long periods (55–90 hours) from late November onwards, likely driven by warmer northwesterly and northeasterly low-speed winds. Increased surface ponding on ice shelves may threaten their stability through increased potential for hydrofracture initiation; a risk that may increase due to firn air content depletion in response to near-surface melting.

Large interannual variability in supraglacial lakes around East Antarctica

“…containing pixels that were classified as lake on at least one day in January) by stacking and merging lake outlines for all dates within January for which we were able to classify lakes. We did this to be able to calculate maximum lake volume masks (below) due to temporally varying satellite paths and/or variable cloud cover around the EAIS margin 63 . We used the REMA (Reference Elevation Model of Antarctica 64 ) mosaic (200-m resolution) to extract SGL elevations.…”

“…For January of each year (2014–2020), we created a maximum lake depth mask by assigning all water pixels in the maximum lake area mask a depth equal to the maximum water depth observed out of all images during January following ref. 63 , using the Cell Statistics tool in ArcGIS. Spatiotemporally variable satellite image acquisition and/or variable cloud cover around the EAIS margin mean that, for different ice shelves, lake depths are calculated on different days in January (Supplementary Fig.…”

Remote Sensing of Surface Melt on Antarctica: Opportunities and Challenges

“…Finally, we used a digital elevation model (DEM) of Antarctica based on CryoSat-2 observations between July 2010 and July 2016 [99] to eliminate elevations over 1700 meters (similar to e.g. [100]), at which melt is not expected.…”

“…Extensive areas of ponded surface water have been observed over the northern part of the George VI Ice Shelf since the early 1940s [100], [114], [115]. Where ASCAT, Sentinel-1, and SSMIS M+3S detect melt of 99%, 97%, and 85% averaged over melt season 2017-2018, this is lower for SSMIS DAV (i.e., 72%) in Fig.…”

Local‐ and Large‐Scale Drivers of Variability in the Coastal Freshwater Budget of the Western Antarctic Peninsula

“…Climatic change at the WAP continues, and recently there have been observations of 32‐year record‐high surface melt rates at George VI Ice Shelf, concurrent with atmospheric temperatures over 20°C at the northern WAP that have been dubbed an Antarctic heatwave (Banwell et al., 2020). Given these extrema and their profound potential implications, combined with limited predictive skill concerning their future evolution, it is important that we improve our mechanistic understanding of the WAP system and its response to climate change.…”