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

2020 ◽  
Vol 14 (11) ◽  
pp. 4103-4120 ◽  
Author(s):  
Jennifer F. Arthur ◽  
Chris R. Stokes ◽  
Stewart S. R. Jamieson ◽  
J. Rachel Carr ◽  
Amber A. Leeson
Keyword(s):  
Climate Model ◽  
Regional Climate ◽  
East Antarctica ◽  
Katabatic Wind ◽  
Ice Shelf ◽  
Ice Shelves ◽  
Shelf Stability ◽  
Seasonal Evolution ◽  
Supraglacial Lakes ◽  
Area And Volume

Abstract. 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 km2, a mean depth of 0.96 m and a mean total meltwater volume of 7.45×106 m3. At their most extensive, SGLs cover a cumulative area of 50.7 km2 and are clustered near to the grounding line, where densities approach 0.27 km2 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.

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

2020 ◽  
Author(s):  
Jennifer F. Arthur ◽  
Chris R. Stokes ◽  
Stewart S. R. Jamieson ◽  
J. Rachel Carr ◽  
Amber A. Leeson
Keyword(s):  
Climate Model ◽  
Regional Climate ◽  
East Antarctica ◽  
Katabatic Wind ◽  
Ice Shelf ◽  
Ice Shelves ◽  
Shelf Stability ◽  
Seasonal Evolution ◽  
Supraglacial Lakes ◽  
Area And Volume

Abstract. 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 km2, a mean depth of 0.96 m, and a mean total meltwater volume of 7.45 x 106 m3. At their most extensive, SGLs cover a cumulative area of 50.7 km2 and are clustered near to the grounding line, where densities approach 0.27 km2 per km2. 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.

Evolution of supraglacial lakes on Shackleton Ice Shelf, East Antarctica

2020 ◽  
Author(s):  
Jennifer Arthur ◽  
Chris Stokes ◽  
Stewart Jamieson ◽  
Rachel Carr ◽  
Amber Leeson
Keyword(s):  
Climate Model ◽  
High Surface ◽  
Surface Melting ◽  
East Antarctica ◽  
Ice Shelf ◽  
Ice Shelves ◽  
Shelf Stability ◽  
Supraglacial Lakes ◽  
Surface Melt ◽  
The Impact

<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>

Inter-annual variability in supraglacial lakes around East Antarctica

2021 ◽  
Author(s):  
Jennifer Arthur ◽  
Chris Stokes ◽  
Stewart Jamieson ◽  
Rachel Carr ◽  
Amber Leeson
Keyword(s):  
Climate Model ◽  
Regional Climate ◽  
Ice Sheet ◽  
Landsat 8 ◽  
Ice Shelf ◽  
Ice Shelves ◽  
Flow Acceleration ◽  
Air Content ◽  
Supraglacial Lakes ◽  
Global Sea Level

<p>Surface meltwater ponding can weaken and trigger the rapid disintegration of Antarctic ice shelves which buttress the ice sheet, causing ice flow acceleration and global sea-level rise. While supraglacial lakes (SGLs) are relatively well documented during some years and selected ice shelves in Antarctica, we have little understanding of how Antarctic-wide SGL coverage varies between melt seasons. Here, we present a record of SGL evolution around the peak of the melt season on the East Antarctic Ice Sheet (EAIS) over seven consecutive years. Our findings are based on a threshold-based algorithm applied to 2175 Landsat 8 images during the month of January from 2014 to 2020. We find that EAIS-wide SGL volume fluctuates inter-annually by up to ~80%. Moreover, patterns within regions and on neighbouring ice shelves are not necessarily synchronous. Over the whole EAIS, total SGL volume was greatest in January 2017, dominated by the Amery and Roi Baudouin ice shelves, and lowest in January 2016. Excluding these two ice shelves, SGL volume peaked in January 2020. Preliminary results suggest EAIS-wide total SGL volume and extent are weakly correlated with firn model simulations of firn air content, surface melt and minimum ice lens depth predicted by the regional climate model MAR. On certain ice shelves, years with peak SGL volume correspond with minimum firn air content. This work provides important constraints for numerical ice-shelf and ice-sheet model predictions of future Antarctic surface meltwater distributions and the potential impact on ice-sheet stability and flow.  </p>

scholarly journals Surface meltwater drainage and ponding on Amery Ice Shelf, East Antarctica, 1973–2019

2021 ◽  
pp. 1-14
Author(s):  
Julian J. Spergel ◽  
Jonathan Kingslake ◽  
Timothy Creyts ◽  
Melchior van Wessem ◽  
Helen A. Fricker
Keyword(s):  
Climate Model ◽  
Regional Climate ◽  
Drainage System ◽  
East Antarctica ◽  
Lake Area ◽  
Ice Shelf ◽  
Ice Shelves ◽  
Lake Volume ◽  
Amery Ice Shelf ◽  
Elevation Model

Abstract Surface melting on Amery Ice Shelf (AIS), East Antarctica, produces an extensive supraglacial drainage system consisting of hundreds of lakes connected by surface channels. This drainage system forms most summers on the southern portion of AIS, transporting meltwater large distances northward, toward the ice front and terminating in lakes. Here we use satellite imagery, Landsat (1, 4 and 8), MODIS multispectral and Sentinel-1 synthetic aperture radar to examine the seasonal and interannual evolution of the drainage system over nearly five decades (1972–2019). We estimate seasonal meltwater input to one lake by integrating output from the regional climate model [Regional Atmospheric Climate Model (RACMO 2.3p2)] over its catchment defined using the Reference Elevation Model of Antarctica. We find only weak positive relationships between modeled seasonal meltwater input and lake area and between meltwater input and lake volume. Consecutive years of extensive melting lead to year-on-year expansion of the drainage system, potentially through a link between melt production, refreezing in firn and the maximum extent of the lakes at the downstream termini of drainage. These mechanisms are important when evaluating the potential of drainage systems to grow in response to increased melting, delivering meltwater to areas of ice shelves vulnerable to hydrofracture.

scholarly journals The Atmospheric River Threat to Antarctic Peninsula Ice-Shelf Stability

2021 ◽  
Author(s):  
Jonathan Wille ◽  
Vincent Favier ◽  
Nicolas Jourdain ◽  
Christoph Kittel ◽  
Jenny Turton ◽  
...  
Keyword(s):  
Antarctic Peninsula ◽  
Climate Model ◽  
Regional Climate ◽  
Detection Algorithm ◽  
Ice Shelf ◽  
Ice Shelves ◽  
Atmospheric River ◽  
The Antarctic ◽  
Collapse Theories ◽  
Temperature Surface

Abstract The disintegration of the ice shelves along the Antarctic Peninsula have spurred much discussion on the various processes leading to their eventual dramatic collapse, but without a consensus on an atmospheric forcing that could connect these processes. Here, using an atmospheric river (AR) detection algorithm along with a regional climate model and satellite observations, we show that particularly intense ARs have a ~40% probability of inducing extreme events of temperature, surface melt, sea-ice disintegration, or large swells; all processes proven to induce ice-shelf destabilization. This was observed during the collapses of the Larsen A, B, and overall, 60% of calving events triggered by ARs from 2000-2020. The loss of the buttressing effect from these ice shelves leads to further continental ice loss and subsequent sea-level rise. Understanding how ARs connect various disparate processes cited in ice-shelf collapse theories is essential for identifying other at-risk ice shelves like the Larsen C.

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

2021 ◽  
Author(s):  
Mariel Christina Dirscherl ◽  
Andreas J. Dietz ◽  
Claudia Kuenzer
Keyword(s):  
Antarctic Peninsula ◽  
Time Lags ◽  
Ice Shelf ◽  
Ice Shelves ◽  
Shelf Stability ◽  
Air Content ◽  
Supraglacial Lakes ◽  
Environmental Controls ◽  
Lake Formation ◽  
Increased Risk

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.

Supplementary material to "Distribution and seasonal evolution of supraglacial lakes on Shackleton Ice Shelf, East Antarctica"

2020 ◽  
Author(s):  
Jennifer F. Arthur ◽  
Chris R. Stokes ◽  
Stewart S. R. Jamieson ◽  
J. Rachel Carr ◽  
Amber A. Leeson
Keyword(s):  
East Antarctica ◽  
Ice Shelf ◽  
Seasonal Evolution ◽  
Supraglacial Lakes ◽  
Supplementary Material

scholarly journals Bathymetry Beneath Ice Shelves of Western Dronning Maud Land, East Antarctica, and Implications on Ice Shelf Stability

2020 ◽  
Vol 47 (12) ◽  
Author(s):  
Hannes Eisermann ◽  
Graeme Eagles ◽  
Antonia Ruppel ◽  
Emma Clare Smith ◽  
Wilfried Jokat
Keyword(s):  
East Antarctica ◽  
Ice Shelf ◽  
Ice Shelves ◽  
Shelf Stability ◽  
Dronning Maud Land

scholarly journals Modelling perennial firn aquifers in the Antarctic Peninsula (1979–2016)

2020 ◽  
Author(s):  
J. Melchior van Wessem ◽  
Christian R. Steger ◽  
Nander Wever ◽  
Michiel R. van den Broeke
Keyword(s):  
Antarctic Peninsula ◽  
Climate Model ◽  
Liquid Water Content ◽  
Ice Shelf ◽  
Ice Shelves ◽  
Supraglacial Lakes ◽  
Order Of Magnitude ◽  
Grid Points ◽  
One Year ◽  
The Antarctic

Abstract. We use two snow models, the IMAU Firn Densification Model (IMAU-FDM) and SNOWPACK, to model firn characteristics in the Antarctic Peninsula (AP). We force these models with mass and energy fluxes from the Regional Atmospheric Climate MOdel (RACMO2.3p2) to construct a 1979–2016 climatology of AP firn density, temperature and liquid water content. A comparison with 75 snow temperature observations at 10 m depth and with density from 11 firn cores, suggests that both snow models perform adequately. In this study, we focus on the detection of so-called perennial firn aquifers (PFAs), that are formed when surface meltwater percolates into the firnpack in summer, is then buried by snowfall, and does not refreeze during the following winter. In 941 model grid points, covering ~ 28,000 km2, PFAs existed for at least one year in the simulated period, most notably in the western AP. At these locations, surface meltwater production exceeds 150 to 300 mm w.e. yr−1, with accumulation at least an order of magnitude larger. Most pronounced and widespread are PFAs modelled on and around Wilkins ice shelf. Here, both meltwater production and accumulation rates are sufficiently high to cause PFA formation in most years in the 1979–2016 period, covering a large part of the ice shelf. Other notable PFA locations are Wordie ice shelf, an ice shelf that has almost completely disappeared in recent decades, and the relatively warm northwestern mountain ranges of Palmer Land, where accumulations rates can be extremely large and PFAs are formed frequently. We find that not only the magnitude of melt and accumulation is important, but also the timing. If large accumulation events occur in the months following an above average summer melt event, this favours PFA formation in that year. Finally, we find that most PFAs are predicted near the grounding lines of the (former) Prince Gustav, Wilkins and Wordie ice shelves. This highlights the need to further investigate how PFAs may impact ice shelf disintegration events, in a similar way as supraglacial lakes do.

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