Through-Ice-Shelf Drainage of Surface Meltwater Lakes and its Implications for Antarctic Ice Shelf Stability

Ice rumples are locally-grounded features of flowing ice shelves, elevated tens of meters above the surrounding surface. These features may significantly impact the dynamics of ice-shelf grounding lines, which are strongly related to shelf stability. In this study, we used TanDEM-X data to construct high-resolution DEMs of the Thwaites ice shelf in West Antarctica from 2011 to 2013. We also generated surface deformation maps which allowed us to detect and monitor the elevation changes of an ice rumple that appeared sometime between the observations of a grounding line of the Thwaites glacier using Double-Differential Interferometric SAR (DDInSAR) in 1996 and 2011. The observed degradation of the ice rumple during 2011–2013 may be related to a loss of contact with the underlying bathymetry caused by the thinning of the ice shelf. We subsequently used a viscoelastic deformation model with a finite spherical pressure source to reproduce the surface expression of the ice rumple. Global optimization allowed us to fit the model to the observed deformation map, producing reasonable estimates of the ice thickness at the center of the pressure source. Our conclusion is that combining the use of multiple high-resolution DEMs and the simple viscoelastic deformation model is feasible for observing and understanding the transient nature of small ice rumples, with implications for monitoring ice shelf stability.

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Brief Communication: Newly developing rift in Larsen C Ice Shelf presents significant risk to stability

The Cryosphere ◽

10.5194/tc-9-1223-2015 ◽

2015 ◽

Vol 9 (3) ◽

pp. 1223-1227 ◽

Cited By ~ 24

Author(s):

D. Jansen ◽

A. J. Luckman ◽

A. Cook ◽

S. Bevan ◽

B. Kulessa ◽

...

Keyword(s):

At Risk ◽

Numerical Model ◽

Significant Risk ◽

Suture Zone ◽

Ice Shelf ◽

Minimum Area ◽

Shelf Stability ◽

Near Future

Abstract. An established rift in the Larsen C Ice Shelf, formerly constrained by a suture zone containing marine ice, grew rapidly during 2014 and is likely in the near future to generate the largest calving event since the 1980s and result in a new minimum area for the ice shelf. Here we investigate the recent development of the rift, quantify the projected calving event and, using a numerical model, assess its likely impact on ice shelf stability. We find that the ice front is at risk of becoming unstable when the anticipated calving event occurs.

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Basal crevasses in Larsen C Ice Shelf and implications for their global abundance

The Cryosphere Discussions ◽

10.5194/tcd-5-2035-2011 ◽

2011 ◽

Vol 5 (4) ◽

pp. 2035-2060 ◽

Cited By ~ 5

Author(s):

A. Luckman ◽

D. Jansen ◽

B. Kulessa ◽

E. C. King ◽

P. Sammonds ◽

...

Keyword(s):

Snow Accumulation ◽

Ice Accretion ◽

Ice Shelf ◽

Ice Shelves ◽

Shelf Stability ◽

Geometrical Properties ◽

Linear Elastic ◽

Grounding Line ◽

Modis Imagery ◽

Elastic Fracture

Abstract. Basal crevasses extend upwards from the base of ice bodies and can penetrate more than halfway through the ice column under conditions found commonly on ice shelves. As a result, they may locally modify the exchange of mass and energy between ice shelf and ocean, and by altering the shelf's mechanical properties could play a fundamental role in ice shelf stability. Although early studies revealed that such features may be abundant on Antarctic ice shelves, their geometrical properties and spatial distribution has gained little attention. We investigate basal crevasses in Larsen C Ice Shelf using field radar survey, remote sensing and numerical modelling. We demonstrate that a group of features visible in MODIS imagery are the surface expressions of basal crevasses in the form of surface troughs, and find that basal crevasses can be generated as a result of stresses well downstream of the grounding line. We show that linear elastic fracture mechanics modelling is a good predictor of basal crevasse penetration height where stresses are predominantly tensile, and that measured surface trough depth does not always reflect this height, probably because of snow accumulation in the trough, marine ice accretion in the crevasse, or stress bridging from the surrounding ice. We conclude that all features visible in MODIS imagery of ice shelves and previously labelled simply as "crevasses", where they are not full thickness rifts, must be basal crevasse troughs, highlighting a fundamental structural property of many ice shelves that may have been previously overlooked.

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

10.5194/tc-2021-203 ◽

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.

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Ice Shelf Stability

Encyclopedia of Ocean Sciences ◽

10.1016/b978-0-12-409548-9.10791-2 ◽

2019 ◽

pp. 127-133

Author(s):

C. Branecky Begeman ◽

C.S.M. Doake

Keyword(s):

Ice Shelf ◽

Shelf Stability

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Ice-shelf Stability

Encyclopedia of Ocean Sciences ◽

10.1006/rwos.2001.0005 ◽

2001 ◽

pp. 1282-1290 ◽

Cited By ~ 3

Author(s):

C.S.M. Doake

Keyword(s):

Ice Shelf ◽

Shelf Stability

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Brief Communication: Newly developing rift in Larsen C Ice Shelf presents significant risk to stability

The Cryosphere Discussions ◽

10.5194/tcd-9-861-2015 ◽

2015 ◽

Vol 9 (1) ◽

pp. 861-872 ◽

Cited By ~ 1

Author(s):

D. Jansen ◽

A. J. Luckman ◽

A. Cook ◽

S. Bevan ◽

B. Kulessa ◽

...

Keyword(s):

At Risk ◽

Numerical Model ◽

Significant Risk ◽

Suture Zone ◽

Ice Shelf ◽

Minimum Area ◽

Shelf Stability ◽

Near Future

Abstract. An established rift in the Larsen C Ice Shelf, formerly constrained by a suture zone containing marine ice, grew rapidly during 2014 and is likely in the near future to generate the largest calving event since the 1980s and result in a new minimum area for the ice shelf. Here we investigate the recent development of the rift, quantify the projected calving event and, using a numerical model, assess its likely impact on ice shelf stability. We find that the ice front is at risk of becoming unstable when the anticipated calving event occurs.

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

10.5194/tc-2020-101 ◽

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.

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An updated seabed bathymetry beneath Larsen C Ice Shelf, west Antarctic

10.5194/essd-2019-205 ◽

2019 ◽

Author(s):

Alex Brisbourne ◽

Bernd Kulessa ◽

Thomas Hudson ◽

Lianne Harrison ◽

Paul Holland ◽

...

Keyword(s):

Ocean Circulation ◽

Tidal Mixing ◽

Gridded Data ◽

Ice Shelf ◽

Data Set ◽

Outlet Glacier ◽

Shelf Stability ◽

Data Product ◽

West Antarctic ◽

Basal Melting

Abstract. In recent decades, rapid ice-shelf disintegration along the Antarctic Peninsula has had a global impact through enhancing outlet glacier flow, and hence sea level rise, and the freshening of Antarctic Bottom Water. Ice shelf thinning due to basal melting results from the circulation of relatively warm water in the underlying ocean cavity. However, the effect of sub-shelf circulation on future ice-shelf stability cannot be predicted accurately with computer simulations if the geometry of the ice-shelf cavity is unknown. To address this deficit for Larsen C Ice Shelf, west Antarctica, we integrate new water-column thickness measurements with existing observations. We present these new data here along with an updated bathymetry grid of the ocean cavity. Key findings include relatively deep seabed to the south-east of the Kenyon Peninsula, along the grounding line and around the key ice shelf pinning point of Bawden Ice Rise. In addition, we can confirm that the cavity’s southern trough stretches from Mobiloil Inlet to the open ocean. These areas of deep seabed will influence ocean circulation and tidal mixing, and will therefore affect the basal-melt distribution. These results will help constrain models of ice-shelf cavity circulation with the aim of improving our understanding of sub-shelf processes and their potential influence on ice shelf stability. The data set comprises all point measurements of seabed depth and a gridded data product, derived using additional measurements of both offshore seabed depth and the thickness of grounded ice. We present all new depth measurements here as well as a compilation of previously published measurements used in the gridding process. The gridded data product is included in the supplementary material. The underlying seismic data sets which were used to determine bed depth and ice thickness are available at https://doi.org/10.5285/315740B1-A7B9-4CF0-9521-86F046E33E9A (Brisbourne et al., 2019), https://doi.org/10.5285/5D63777D-B375-4791-918F-9A5527093298 (Booth, 2019), https://doi.org/10.5285/FFF8AFEE-4978-495E-9210-120872983A8D (Kulessa and Bevan, 2019) and https://doi.org/10.5285/147BAF64-B9AF-4A97-8091-26AEC0D3C0BB (Booth et al., 2019).

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Airborne and ground-based geophysical evaluation of the surface and englacial hydrological system of the Sørsdal Glacier, East Antarctica, and implications for ice-shelf stability

10.5194/egusphere-egu21-14890 ◽

2021 ◽

Author(s):

Bernd Kulessa ◽

Sarah Thompson ◽

Sue Cook ◽

Glenn Jones ◽

Christopher Watson ◽

...

Keyword(s):

Temporal Evolution ◽

Austral Summer ◽

East Antarctica ◽

Ice Shelf ◽

Ice Dynamics ◽

Shelf Stability ◽

Passive Seismic ◽

Hydrological System ◽

Ground Penetrating ◽

The Antarctic

<p>Large swathes of the margin of the East Antarctic Ice Sheet experience pronounced surface melting during the austral summer. The nature and temporal evolution of evolving surface hydrological systems are poorly known, however, as are their potential connections with englacial and subglacial water systems and their effects on ice dynamics. We have acquired helicopter-based ground-penetrating radar (GPR), electrical self-potential (SP), broadband passive seismic and GNSS data to delineate the geometry and monitor the temporal evolution of the subsurface hydrological system of the marine-terminating S&#248;rsdal Glacier, Princess Elizabeth Land, East Antarctica, between the austral summers of 2017-18 and 2018-19. Our data reveal the presence of a shallow englacial hydrological system that is connected to surface lakes upstream of the grounding line and, surprisingly, is active not only in the austral summer but also through the Antarctic winter. Here we illustrate the spatial and temporal characteristics of the englacial hydrological system and its susceptibility to tidal forcing through the Antarctic winter. Our observations are consistent with persistent year-round redistribution of mass from grounded to floating portions of at the East Antarctic margin, with far-reaching consequences for ice shelf stability.</p>

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