Search

Antarctic supraglacial lakes (SGLs) have been linked to ice shelf collapse and the subsequent acceleration of inland ice flow, but observations of SGLs remain relatively scarce and their interannual variability is largely unknown. This makes it difficult to assess whether some ice shelves are close to thresholds of stability under climate warming. Here, we present the first observations of SGLs across the entire East Antarctic Ice Sheet over multiple melt seasons (2014–2020). Interannual variability in SGL volume is >200% on some ice shelves, but patterns are highly asynchronous. More extensive, deeper SGLs correlate with higher summer (December-January-February) air temperatures, but comparisons with modelled melt and runoff are complex. However, we find that modelled January melt and the ratio of November firn air content to summer melt are important predictors of SGL volume on some potentially vulnerable ice shelves, suggesting large increases in SGLs should be expected under future atmospheric warming. Antarctic supraglacial lakes (SGLs) have been linked to ice-shelf collapse and the subsequent acceleration of inland ice flow, but observations of SGLs remain relatively scarce and their interannual variability is largely unknown. This new study shows that lake area and volume vary substantially from year-to-year around the East Antarctic Ice Sheet and between ice shelves. [ABSTRACT FROM AUTHOR]

The weakening and/or removal of floating ice shelves in Antarctica can induce inland ice flow acceleration. Numerical modelling suggests these processes will play an important role in Antarctica's future sea-level contribution, but our understanding of the mechanisms that lead to ice tongue/shelf collapse is incomplete and largely based on observations from the Antarctic Peninsula and West Antarctica. Here, we use remote sensing of structural glaciology and ice velocity from 2001 to 2020 and analyse potential ocean-climate forcings to identify mechanisms that triggered the rapid disintegration of ~2445 km2 of ice mélange and part of the Voyeykov Ice Shelf in Wilkes Land, East Antarctica between 27 March and 28 May 2007. Results show disaggregation was pre-conditioned by weakening of the ice tongue's structural integrity and was triggered by mélange removal driven by a regional atmospheric circulation anomaly and a less extensive latent-heat polynya. Disaggregation did not induce inland ice flow acceleration, but our observations highlight an important mechanism through which floating termini can be removed, whereby the break-out of mélange and multiyear landfast sea ice triggers disaggregation of a structurally-weak ice shelf. These observations highlight the need for numerical ice-sheet models to account for interactions between sea-ice, mélange and ice shelves. [ABSTRACT FROM AUTHOR]

Supraglacial lakes (SGLs) are now known to be widespread in Antarctica, where they represent an important component of ice sheet mass balance. This paper reviews how recent progress in satellite remote sensing has substantially advanced our understanding of SGLs in Antarctica, including their characteristics, geographic distribution and impacts on ice sheet dynamics. Important advances include: (a) the capability to resolve lakes at sub-metre resolution at weekly timescales; (b) the measurement of lake depth and volume changes at seasonal timescales, including sporadic observations of lake drainage events and (c) the integration of multiple optical satellite datasets to obtain continent-wide observations of lake distributions. Despite recent progress, however, there remain important gaps in our understanding, most notably: (a) the relationship between seasonal variability in SGL development and near-surface climate; (b) the prevalence and impact of SGL drainage events on both grounded and floating ice and (c) the sensitivity of individual ice shelves to lake-induced hydrofracture. Given that surface melting and SGL development is predicted to play an increasingly important role in the surface mass balance of Antarctica, bridging these gaps will help constrain predictions of future rapid ice loss from Antarctica. [ABSTRACT FROM AUTHOR]

Supraglacial lakes (SGLs) enhance surface melting and can flex and fracture ice shelves when they grow and subsequently drain, potentially leading to ice shelf disintegration. However, the seasonal evolution of SGLs and their influence on ice shelf stability in East Antarctica remains poorly understood, despite some potentially vulnerable ice shelves having high densities of SGLs. Using optical satellite imagery, air temperature data from climate reanalysis products and surface melt predicted by a regional climate model, we present the first long-term record (2000–2020) of seasonal SGL evolution on Shackleton Ice Shelf, which is Antarctica's northernmost remaining ice shelf and buttresses Denman Glacier, a major outlet of the East Antarctic Ice Sheet. In a typical melt season, we find hundreds of SGLs with a mean area of 0.02 km 2 , a mean depth of 0.96 m and a mean total meltwater volume of 7.45×106 m 3. At their most extensive, SGLs cover a cumulative area of 50.7 km 2 and are clustered near to the grounding line, where densities approach 0.27 km 2 km -2. Here, SGL development is linked to an albedo-lowering feedback associated with katabatic winds, together with the presence of blue ice and exposed rock. Although below-average seasonal (December–January–February, DJF) temperatures are associated with below-average peaks in total SGL area and volume, warmer seasonal temperatures do not necessarily result in higher SGL areas and volumes. Rather, peaks in total SGL area and volume show a much closer correspondence with short-lived high-magnitude snowmelt events. We therefore suggest seasonal lake evolution on this ice shelf is instead more sensitive to snowmelt intensity associated with katabatic-wind-driven melting. Our analysis provides important constraints on the boundary conditions of supraglacial hydrology models and numerical simulations of ice shelf stability. [ABSTRACT FROM AUTHOR]