Seasonal evolution of Antarctic supraglacial lakes in 2015–2021 and links to environmental controls

Abstract

Abstract. Supraglacial meltwater accumulation on ice shelves may have important implications for future sea-level-rise. Despite recent progress in the understanding of Antarctic surface hydrology, potential influences on ice shelf stability as well as links to environmental drivers remain poorly constrained. In this study, we employ state-of-the-art machine learning on Sentinel-1 Synthetic Aperture Radar (SAR) and optical Sentinel-2 satellite imagery to provide new insight into the inter-annual and intra-annual evolution of surface hydrological features across six major Antarctic Peninsula and East Antarctic ice shelves. For the first time, we produce a record of supraglacial lake extent dynamics for the period 2015–2021 at unprecedented 10 m spatial resolution and bi-weekly temporal scale. Through synergetic use of optical and SAR data, we obtain a more complete mapping record enabling the delineation of also buried lakes. Our results for Antarctic Peninsula ice shelves reveal below average meltwater ponding during most of melting seasons 2015–2018 and above average meltwater ponding throughout summer 2019–2020 and early 2020–2021. Meltwater ponding on investigated East Antarctic ice shelves was far more variable with above average lake extents during most of melting seasons 2016–2019 and below average lake extents during 2020–2021. This study is the first to investigate relationships with climate drivers both, spatially and temporally including time lag analysis. The results indicate that supraglacial lake formation in 2015–2021 is coupled to the complex interplay of varying air temperature, solar radiation, snowmelt, wind and precipitation, each at different time lags and directions and with strong local to regional discrepancies, as revealed through pixel-based correlation analysis. Southern Hemisphere atmospheric modes as well as the local glaciological setting including melt-albedo feedbacks and the firn air content were revealed to strongly influence the spatio-temporal evolution of supraglacial lakes as well as below or above average meltwater ponding despite variations in the strength of forcing. Recent increases of Antarctic Peninsula surface ponding point towards a further reduction of the firn air content implying an increased risk for ponding and hydrofracture. In addition, lateral meltwater transport was observed over both Antarctic regions with similar implications for future ice shelf stability.

Large interannual variability in supraglacial lakes around East Antarctica

“…5 , Supplementary Table 4 ). This implies that more extensive, deeper SGLs form in warmer melt seasons when there is more melting, in agreement with previous observations in East Antarctica 26 , 29 , 31 and on the Antarctic Peninsula 43 . The two regions of the ice sheet where DJF T 2m is most strongly positively correlated with total SGL volumes are the Riiser-Larsen ( r = 0.67, p = 0.03) and West ice shelves ( r = 0.79, p = 0.01) (Fig.…”

“…Most SGLs form around or just downstream of low-albedo blue (bare) ice regions close to ice shelf grounding lines, where snow and firn have been entirely removed by persistent katabatic wind erosion, sublimation or melt 15 , 26 , 29 . Here, there is regular melting because the reduced albedo increases shortwave radiation absorption, and katabatic winds maintain enhanced turbulent surface heating 29 , 31 . This enables SGLs to form at high elevations where low-albedo exposed bedrock and blue ice are abundant 15 , 23 (Fig.…”

“…However, there is limited knowledge of the interannual variability in SGLs over multiple melt seasons and across the whole ice sheet. There have also been few attempts to link the spatial and temporal variability in SGLs on ice shelves to near-surface climatic conditions 22 , 26 , 30 , 31 . Here, we quantify the variability in SGL distributions and volumes around the East Antarctic Ice Sheet (EAIS) during the peak of seven consecutive melt seasons (2014–2020) and investigate potential climatic controls on their development and near-surface (i.e.…”

Regional variability of diatoms in ice cores from the Antarctic Peninsula and Ellsworth Land, Antarctica

“…Despite the widespread glacier retreat across the AP, the recent formation of these landforms is mostly constrained to the northern Antarctic Peninsula (Ruiz-Fernández et al, 2019). Additionally, recent increases in air temperatures and strengthened poleward flow on the western Antarctic Peninsula have promoted the formation of seasonal supraglacial water bodies on top of glaciers and ice shelves (Dirscherl et al, 2021).…”

“…Diatoms have been found in low concentrations in Antarctic subglacial, supraglacial, and epishelf lakes, and cryoconite holes (Smith et al, 2006;Hodgson et al, 2009;Keskitalo et al, 2013;Stanish et al, 2013). However, these non-marine water bodies are confined, scarce, and very localized along the Amundsen-Bellingshausen coast, all located at low-elevation sites and either seasonally or perennially ice-lidded due to low temperatures year-round (Giralt et al, 2020;Dirscherl et al, 2021). Similarly, cryoconite holes have only been reported in regions distant from the ice core sites, such as the northern tip of the Antarctic Peninsula (South Shetland Islands) (Buda et al, 2020), the McMurdo Dry Valleys in Victoria Land (Fountain et al, 2004;MacDonell et al, 2016;Darcy et al, 2018), and the coast of Dronning Maud Land (Weisleitner et al, 2020), all exposed to the same icelidded conditions (Buda et al, 2020).…”