scholarly journals Brief communication: Heterogenous thinning and subglacial lake activity on Thwaites Glacier, West Antarctica

2020 ◽  
Vol 14 (12) ◽  
pp. 4603-4609
Author(s):  
Andrew O. Hoffman ◽  
Knut Christianson ◽  
Daniel Shapero ◽  
Benjamin E. Smith ◽  
Ian Joughin
Keyword(s):  
Time Series ◽  
Austral Winter ◽  
West Antarctica ◽  
Subglacial Lake ◽  
Satellite Velocity ◽  
Ice Velocity ◽  
Subglacial Lakes ◽  
Speed Fluctuations ◽  
Lake Systems

Abstract. A system of subglacial lakes drained on Thwaites Glacier from 2012–2014. To improve coverage for subsequent drainage events, we extended the elevation and ice-velocity time series on Thwaites Glacier through austral winter 2019. These new observations document a second drainage cycle in 2017/18 and identified two new lake systems located in the western tributaries of Thwaites and Haynes glaciers. In situ and satellite velocity observations show temporary < 3 % speed fluctuations associated with lake drainages. In agreement with previous studies, these observations suggest that active subglacial hydrology has little influence on thinning and retreat of Thwaites Glacier on decadal to centennial timescales.

scholarly journals Brief Communication: Heterogenous thinning and subglacial lake activity on Thwaites Glacier, West Antarctica

2020 ◽  
Author(s):  
Andrew O. Hoffman ◽  
Knut Christianson ◽  
Daniel Shapero ◽  
Benjamin E. Smith ◽  
Ian Joughin
Keyword(s):  
Time Series ◽  
Austral Winter ◽  
West Antarctica ◽  
Subglacial Lake ◽  
Satellite Velocity ◽  
Ice Velocity ◽  
Subglacial Lakes ◽  
Lake Systems

Abstract. A system of subglacial lakes drained on Thwaites Glacier from 2012–2014. To improve coverage for subsequent drainage events, we extended the elevation and ice velocity time series on Thwaites Glacier through austral winter 2019. These new observations document a second drainage cycle and identified two new lake systems located in the western tributaries of Thwaites and Haynes Glaciers. In situ and satellite velocity observations show temporary

scholarly journals Subglacial Lake CECs: Discovery and in situ survey of a privileged research site in West Antarctica

2015 ◽  
Vol 42 (10) ◽  
pp. 3944-3953 ◽  
Author(s):  
Andrés Rivera ◽  
José Uribe ◽  
Rodrigo Zamora ◽  
Jonathan Oberreuter
Keyword(s):  
West Antarctica ◽  
Subglacial Lake ◽  
Research Site

scholarly journals Basal melting over Subglacial Lake Ellsworth and its catchment: insights from englacial layering

2020 ◽  
Vol 61 (81) ◽  
pp. 198-205
Author(s):  
Neil Ross ◽  
Martin Siegert
Keyword(s):  
High Resolution ◽  
West Antarctica ◽  
Microbial Life ◽  
Lake Vostok ◽  
Subglacial Lake ◽  
Lake Outlet ◽  
Hydrological System ◽  
Subglacial Lakes ◽  
Basal Melting ◽  
Insight Into

AbstractDeep-water ‘stable’ subglacial lakes likely contain microbial life adapted in isolation to extreme environmental conditions. How water is supplied into a subglacial lake, and how water outflows, is important for understanding these conditions. Isochronal radio-echo layers have been used to infer where melting occurs above Lake Vostok and Lake Concordia in East Antarctica but have not been used more widely. We examine englacial layers above and around Lake Ellsworth, West Antarctica, to establish where the ice sheet is ‘drawn down’ towards the bed and, thus, experiences melting. Layer drawdown is focused over and around the northwest parts of the lake as ice, flowing obliquely to the lake axis becomes afloat. Drawdown can be explained by a combination of basal melting and the Weertman effect, at the transition from grounded to floating ice. We evaluate the importance of these processes on englacial layering over Lake Ellsworth and discuss implications for water circulation and sediment deposition. We report evidence of a second subglacial lake near the head of the hydrological catchment and present a new high-resolution bed DEM and hydropotential model of the lake outlet zone. These observations provide insight into the connectivity between Lake Ellsworth and the wider subglacial hydrological system.

scholarly journals Connected subglacial lake activity on lower Mercer and Whillans Ice Streams, West Antarctica, 2003–2008

2009 ◽  
Vol 55 (190) ◽  
pp. 303-315 ◽  
Author(s):  
Helen Amanda Fricker ◽  
Ted Scambos
Keyword(s):  
Water Movement ◽  
Quantitative Information ◽  
West Antarctica ◽  
Ice Streams ◽  
Image Differencing ◽  
Subglacial Lake ◽  
Modis Image ◽  
Hydrologic System ◽  
Image Pairs ◽  
Subglacial Lakes

AbstractWe examine patterns of localized surface elevation change in lower Mercer and Whillans Ice Streams, West Antarctica, which we interpret as subglacial water movement through a system of lakes and channels. We detect and measure the lake activity using repeat-track laser altimetry from ICESat and image differencing from MODIS image pairs. A hydrostatic-potential map for the region shows that the lakes are distributed across three distinct hydrologic regimes. Our analysis shows that, within these regimes, some of the subglacial lakes appear to be linked, with drainage events in one reservoir causing filling and follow-on drainage in adjacent lakes. We also observe changes near ice raft ‘a’ in lower Whillans Ice Stream, and interpret them as evidence of subglacial water and other changes at the bed. The study provides quantitative information about the properties of this complex subglacial hydrologic system, and a relatively unstudied component of ice-sheet mass balance: subglacial drainage across the grounding line.

scholarly journals The "tipping" temperature within Subglacial Lake Ellsworth, West Antarctica and its implications for lake access

2011 ◽  
Vol 5 (2) ◽  
pp. 1003-1020 ◽  
Author(s):  
M. Thoma ◽  
K. Grosfeld ◽  
C. Mayer ◽  
A. M. Smith ◽  
J. Woodward ◽  
...  
Keyword(s):  
Lake Water ◽  
Critical Pressure ◽  
Empirical Equation ◽  
Time Span ◽  
West Antarctica ◽  
Subglacial Lake ◽  
The North ◽  
Temperature Regimes ◽  
Subglacial Lakes ◽  
Semi Empirical

Abstract. We present results from new geophysical data allowing 3-D modelling of the water flow within Subglacial Lake Ellsworth (SLE), West Antarctica. Our simulations indicate that this lake has a novel temperature distribution due to significantly thinner ice than other surveyed subglacial lakes. The critical pressure boundary (tipping depth), established from the semi-empirical Equation of State, defines whether the lake's flow regime is convective or stratified. It passes through SLE and separates different temperature (and flow) regimes on either side of the lake. Our results have implications for the location of proposed access holes into SLE, the choice of which will depend on scientific or operational priorities. If an understanding of subglacial lake water properties and dynamics is the priority, holes are required in a basal freezing area at the North end of the lake. This would be the preferred priority suggested by this paper, requiring temperature and salinity profiles in the water column. A location near the Southern end, where bottom currents are lowest, is optimum for detecting the record of life in the bed sediments; to minimise operational risk and maximise the time span of a bed sediment core, a location close to the middle of the lake, where the basal interface is melting and the lake bed is at its deepest, remains the best choice. Considering potential lake-water salinity and ice-density variations, we estimate the critical tipping depth, separating different temperature regimes within subglacial lakes, to be in about 2900 to 3045 m depth.

scholarly journals The "tipping" temperature within Subglacial Lake Ellsworth, West Antarctica and its implications for lake access

2011 ◽  
Vol 5 (3) ◽  
pp. 561-567 ◽  
Author(s):  
M. Thoma ◽  
K. Grosfeld ◽  
C. Mayer ◽  
A. M. Smith ◽  
J. Woodward ◽  
...  
Keyword(s):  
Lake Water ◽  
Critical Pressure ◽  
Empirical Equation ◽  
Time Span ◽  
West Antarctica ◽  
Subglacial Lake ◽  
The North ◽  
Temperature Regimes ◽  
Subglacial Lakes ◽  
Semi Empirical

Abstract. We present results from new geophysical data allowing modelling of the water flow within Subglacial Lake Ellsworth (SLE), West Antarctica. Our simulations indicate that this lake has a novel temperature distribution due to significantly thinner ice than other surveyed subglacial lakes. The critical pressure boundary (tipping depth), established from the semi-empirical Equation of State, defines whether the lake's flow regime is convective or stratified. It passes through SLE and separates different temperature (and flow) regimes on either side of the lake. Our results have implications for the location of proposed access holes into SLE, the choice of which will depend on scientific or operational priorities. If an understanding of subglacial lake water properties and dynamics is the priority, holes are required in a basal freezing area at the North end of the lake. This would be the preferred priority suggested by this paper, requiring temperature and salinity profiles in the water column. A location near the Southern end, where bottom currents are lowest, is optimum for detecting the record of life in the bed sediments; to minimise operational risk and maximise the time span of a bed sediment core, a location close to the middle of the lake, where the basal interface is melting and the lake bed is at its deepest, remains the best choice. Considering potential lake-water salinity and ice-density variations, we estimate the critical tipping depth, separating different temperature regimes within subglacial lakes, to be in about 2900 to 3045 m depth.

scholarly journals Basal melting over Subglacial Lake Ellsworth and its catchment: insights from englacial layering

2020 ◽  
Author(s):  
Neil Ross ◽  
Martin Siegert
Keyword(s):  
High Resolution ◽  
West Antarctica ◽  
Microbial Life ◽  
Lake Vostok ◽  
Subglacial Lake ◽  
Lake Outlet ◽  
Hydrological System ◽  
Subglacial Lakes ◽  
Basal Melting ◽  
Insight Into

&lt;p&gt;Deep-water &amp;#8216;stable&amp;#8217; subglacial lakes likely contain microbial life adapted in isolation to extreme environmental conditions. How water is supplied into a subglacial lake, and how water outflows, is important for understanding these conditions. Isochronal radio-echo layers have been used to infer where melting occurs above Lake Vostok and Lake Concordia in East Antarctica but have not been used more widely. We examine englacial layers above and around Lake Ellsworth, West Antarctica, to establish where the ice sheet is &amp;#8216;drawn down&amp;#8217; towards the bed and, thus, experiences melting. Layer drawdown is focused over and around the NW parts of the lake as ice, flowing obliquely to the lake axis, becomes afloat. Drawdown can be explained by a combination of basal melting and the Weertman effect, at the transition from grounded to floating ice. We evaluate the importance of these processes on englacial layering over Lake Ellsworth and discuss implications for water circulation and sediment deposition. We report evidence of a second subglacial lake near the head of the hydrological catchment and present a new high-resolution bed DEM and hydropotential model of the lake outlet zone. These observations provide insight into the connectivity between Lake Ellsworth and the wider subglacial hydrological system.&lt;/p&gt;

scholarly journals Past water flow beneath Pine Island and Thwaites glaciers, West Antarctica

2019 ◽  
Author(s):  
James D. Kirkham ◽  
Kelly A. Hogan ◽  
Robert D. Larter ◽  
Neil S. Arnold ◽  
Frank O. Nitsche ◽  
...  
Keyword(s):  
Water Flow ◽  
Ice Sheet ◽  
Dry Valleys ◽  
West Antarctica ◽  
Ice Streams ◽  
Subglacial Lake ◽  
Lake Drainage ◽  
Subglacial Lakes ◽  
Glacial Periods ◽  
The Antarctic

Abstract. Outburst floods from subglacial lakes beneath the Antarctic Ice Sheet modulate ice flow velocities over periods of months to years. Although subglacial lake drainage events have been observed from satellite altimetric data, little is known about their role in the long term evolution of ice sheet basal hydrology. Here, we systematically map and model past water flow through an extensive area containing over 1000 subglacial channels and 19 former lake basins exposed on over 19,000 km2 of seafloor by the retreat of Pine Island and Thwaites glaciers, West Antarctica. At 560 m wide and 50 m deep on average, the channels offshore of present day Pine Island and Thwaites glaciers are approximately twice as deep, three times as wide, and cover an area over 400 times larger than the terrestrial meltwater channels comprising the Labyrinth in the Antarctic Dry Valleys. The channels incised into bedrock offshore of contemporary Pine Island and Thwaites glaciers would have been capable of accommodating discharges of up to 8.8 × 106 m3 s−1. We suggest that the channels were formed by episodic, high magnitude discharges from subglacial lakes trapped during ice sheet advance and retreat over multiple glacial periods. Our results document the widespread influence of episodic subglacial drainage events during past glacial periods, in particular beneath large ice streams similar to those that continue to dominate contemporary ice-sheet discharge.

scholarly journals Connected subglacial lake drainage beneath Thwaites Glacier, West Antarctica

2016 ◽  
Author(s):  
Benjamin E. Smith ◽  
Noel Gourmelen ◽  
Alexander Huth ◽  
Ian Joughin
Keyword(s):  
Water Flow ◽  
Large Scale ◽  
Potential Gradient ◽  
Altimetry Data ◽  
West Antarctica ◽  
Subglacial Lake ◽  
Speed Change ◽  
Lake Drainage ◽  
Subglacial Lakes ◽  
Scale Motion

Abstract. We present conventional and swath altimetry data from Cryosat-2 revealing a system of subglacial lakes that drained between June 2013 and January 2014 under the central part of Thwaites Glacier, West Antarctica. Much of the drainage happened in less than six months, with an apparent connection between three lakes spanning more than 130 km. Hydropotential analysis of the glacier bed shows a large number of small closed basins that should trap water produced by subglacial melt, although the observed large-scale motion of water suggests that water can sometimes locally move against the apparent potential gradient, at least during lake-drainage events, suggesting that there are important limitations in the ability of hydropotential maps to predict subglacial water flow. An interpretation based on a map of the melt rate suggests that lake drainages of this type should take place every 20–80 years, depending on the connectivity of the water flow at the bed. Although we observed an acceleration in the downstream part of TWG immediately before the start of the lake drainage, there is no clear connection between the drainage and any speed change of the glacier.

scholarly journals Thirteen years of subglacial lake activity in Antarctica from multi-mission satellite altimetry

2018 ◽  
Vol 59 (76pt1) ◽  
pp. 42-55 ◽  
Author(s):  
Matthew R. Siegfried ◽  
Helen A. Fricker
Keyword(s):  
Time Series ◽  
Ice Sheet ◽  
Surface Expression ◽  
Ice Dynamics ◽  
Ice Cloud ◽  
Subglacial Lake ◽  
Near Term ◽  
Velocity Changes ◽  
Subglacial Lakes ◽  
The Antarctic

ABSTRACTThe ability to detect the surface expression of moving water beneath the Antarctic ice sheet by satellite has revealed a dynamic basal environment, with implications for regional ice dynamics, grounding-line stability, and fluxes of freshwater and nutrients to the Southern Ocean. Knowledge of subglacial activity on timescales important for near-term prediction of ice-sheet fluctuations (decadal to century) is limited by the short observational record of NASA's Ice, Cloud, and land Elevation Satellite (ICESat) laser altimetry mission used to generate the last continent-wide survey (2003–08). Here, we use synthetic aperture radar-interferometric-mode data from ESA's CryoSat-2 radar altimetry mission (2010–present), which samples 45 of the ICESat-derived subglacial lakes, to extend their time series to the end of 2016. The extended time series show that there have been surface-height changes at 20 of the 45 lakes since 2008, indicating that some of these features are persistent and potentially cyclic, while other features show negligible changes, suggesting these may be transient or nonhydrological features. Continued monitoring of active lakes for both height and velocity changes, as well as developing methods for identifying additional lakes, is critical to quantifying the full distribution of active subglacial lakes in Antarctica.

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