Evolution of supraglacial lakes on Shackleton Ice Shelf, East Antarctica

Abstract

<p>Supraglacial lakes (SGLs) enhance surface melting and their development and subsequent drainage can flex and fracture ice shelves, leading to their disintegration. However, the seasonal evolution of SGLs and their potential influence on ice shelf stability in East Antarctica remains poorly understood, despite a number of potentially vulnerable ice shelves. Using optical satellite imagery, climate reanalysis data and surface melt predicted by a regional climate model, we provide the first multi-year analysis (1974-2019) of seasonal SGL evolution on Shackleton Ice Shelf in Queen Mary Land, which is Antarctica’s northernmost remaining ice shelf. We mapped >43,000 lakes on the ice shelf and >5,000 lakes on grounded ice over the 45-year analysis period, some of which developed up to 12 km inland from the grounding line. Lakes clustered around the ice shelf grounding zone are strongly linked to the presence of blue ice and exposed rock, associated with an albedo-lowering melt-enhancing feedback. Lakes either drain supraglacially, refreeze at the end of the melt season, or shrink in-situ. Furthermore, we observe some relatively rapid (≤ 7 days) lake drainage events and infer that some lakes may be draining by hydrofracture. Our observations suggest that enhanced surface meltwater could increase the vulnerability of East Antarctic ice shelves already preconditioned for hydrofracture, namely those experiencing high surface melt rates, firn air depletion, and extensional stress regimes with minimum topographic confinement. Our results could be used to constrain simulations of current melt conditions on the ice shelf and to investigate the impact of increased surface melting on future ice shelf stability.</p>

Distribution and seasonal evolution of supraglacial lakes on Shackleton Ice Shelf, East Antarctica

“…Although RACMO2.3p1 output is available at a 5.5 km resolution in some regions of Antarctica, it does not yet extend to our study region. This finding underscores the need for finer-resolution regional climate model simulations of surface melt when considering future lake distributions (Arthur et al, 2020a;Stokes et al, 2019). The weak relationship that we observe between SGL extents and near-surface temperature is perhaps unsurprising given the resolution of ERA5 is insufficient to resolve localised mixing and albedo-lowering processes around the ice shelf grounding zone, but our preliminary comparison between SGL development and climate offers some clear hints that short-lived melt events are more important than longer-term seasonal conditions.…”

“…This version of the NDWI has been widely applied for mapping surface meltwater in Antarctica (Arthur et al, 2020a;Banwell et al, 2019;Bell et al, 2017) and Greenland (Doyle et al, 2013;Williamson et al, 2017;Yang and Smith, 2013). We found NDWI ice produced fewer false SGL classifications over blue-ice and slush areas than with other versions of the NDWI, such as those using the near-infrared band (Fig.…”

“…Data availability. The supraglacial lake extents and depths discussed in this paper are available at https://doi.org/10.5285/649bbe03-8109-45be-92e5-bcef44a4703a (Arthur et al, 2020a). Sentinel imagery is available from the Copernicus Open Access Hub (https://scihub.copernicus.eu, last access: February 2020; Copernicus Open Access Hub, 2020), and Landsat scenes are available from United States Geological Survey EarthExplorer (https://earthexplorer.usgs.gov/, last access: February 2020; EarthExplorer, 2020).…”

“…Supraglacial lakes (SGLs) are widespread around the margins of Antarctica and can influence ice shelf dynamics both directly and indirectly (Arthur et al, 2020a;Stokes et al, 2019). Ice shelves flex when SGLs pond and drain on their surfaces, which can weaken them and make them more prone to break-up (Banwell et al, 2013(Banwell et al, , 2019Banwell and MacAyeal, 2015).…”

“…Thus, the evolution and interaction of SGLs on ice shelves has important consequences for the stability of ice shelves, many of which exert a buttressing effect on inland ice flow (Fürst et al, 2016(Fürst et al, ). et al, 2017Langley et al, 2016;Lenaerts et al, 2017;Moussavi et al, 2020;Kingslake et al, 2017;Stokes et al, 2019) and are particularly widespread on the Antarctic Peninsula and around the margins of the East Antarctic Ice Sheet (Arthur et al, 2020a;Kingslake et al, 2017;Stokes et al, 2019). However, few studies have conducted detailed analyses of the seasonal behaviour and spatial distribution of SGLs on ice shelves in East Antarctica.…”