Intra- and inter-annual melt water patterns on George VI Ice Shelf, Antarctic Peninsula, from synthetic aperture radar and optical satellite imagery

Meltwater retention on the surface of ice shelves may lead to hydrofracturing and ultimately their breakup and collapse. Several methods have been used to map surface meltwater on ice shelves from satellite imagery, but a comparison of the methods and a systematic analysis of the results has not been undertaken. Here we bring together two recent inventories of surface meltwater features that use machine learning technologies to map: i) ponds from both Sentinel-2 optical and Sentinel-1 SAR imagery; and ii) both ponds and slush from Landsat 8 optical imagery. We analyse the meltwater products at a bi-monthly (twice a month) timescale over six austral summers between November 2015 and March 2021 for the George VI Ice Shelf, Antarctic Peninsula. We investigate the data sets to reveal the seasonal evolution of surface and shallow subsurface meltwater in terms of the onset, cessation and therefore duration of slush and ponded water, as well as the persistency of slush and ponded water areas from year to year. We find areas where the evolution follows similar patterns from year to year, but also highly anomalous patterns and timings in other years. Finally, a systematic analysis of Sentinel 1 imagery throughout the winter seasons reveals several perennial shallow surface water bodies.