scholarly journals Repeat Subglacial Lake Drainage and Filling Beneath Thwaites Glacier

2021 ◽  
Author(s):  
George Malczyk ◽  
Noel Gourmelen ◽  
Daniel Goldberg ◽  
Jan Wuite ◽  
Thomas Nagler
Keyword(s):  
High Resolution ◽  
Closed System ◽  
Drainage System ◽  
Subglacial Lake ◽  
New Methods ◽  
Potential Applications ◽  
Ice Sheet Mass Balance ◽  
Lake Drainage ◽  
Subglacial Lakes ◽  
Subglacial Environments

<p>Active subglacial lakes have been identified throughout Antarctica, offering a window into subglacial environments and their impact on ice sheet mass balance. We use high-resolution altimetry measurements over the Thwaites Glacier to show that a lake system underwent a second episode of drainage activity in 2017, only four years after another substantial drainage event. Our observations suggest significant modifications of the drainage system between the two events, with 2017 experiencing greater upstream discharge, faster lake-to-lake connectivity, and the transfer of water within a closed system. Measured rates of lake recharge during the inter-drainage period are significantly larger than modelled estimates, suggesting processes which drive subglacial melt production are currently underestimated. Our study highlights new methods of exploring subglacial environments through the application of altimetry, with potential applications for studying subglacial lakes across Antarctica</p>

scholarly journals Investigating the stability of subglacial lakes with a full Stokes ice-sheet model

2008 ◽  
Vol 54 (185) ◽  
pp. 353-361 ◽  
Author(s):  
Frank Pattyn
Keyword(s):  
Ice Sheet ◽  
Drainage System ◽  
Potential Gradient ◽  
Surface Slope ◽  
Ice Flow ◽  
Subglacial Lake ◽  
Lake Drainage ◽  
Subglacial Lakes ◽  
The Impact ◽  
Subglacial Drainage

AbstractDespite the large amount of subglacial lakes present underneath the East Antarctic ice sheet and the melt processes involved, the hydrology beneath the ice sheet is poorly understood. Changes in subglacial potential gradients may lead to subglacial lake outbursts, discharging excess water through a subglacial drainage system underneath the ice sheet. Such processes can eventually lead to an increase in ice flow. In this paper, a full Stokes numerical ice-sheet model was employed which takes into account the ice flow over subglacial water bodies in hydrostatic equilibrium with the overlying ice. Sensitivity experiments were carried out for small perturbations in ice flow and basal melt rate as a function of ice thickness, general surface slope, ice viscosity and lake size, in order to investigate their influence on the subglacial potential gradient and the impact on subglacial lake drainage. Experiments clearly demonstrate that small changes in surface slope are sufficient to start and sustain episodic subglacial drainage events. Lake drainage can therefore be regarded as a common feature of the subglacial hydrological system and may influence, to a large extent, the present and future behavior of large ice sheets.

scholarly journals Modeling Antarctic subglacial lake filling and drainage cycles

2016 ◽  
Vol 10 (4) ◽  
pp. 1381-1393 ◽  
Author(s):  
Christine F. Dow ◽  
Mauro A. Werder ◽  
Sophie Nowicki ◽  
Ryan T. Walker
Keyword(s):  
Internal Controls ◽  
Water Volume ◽  
Lake Basin ◽  
Subglacial Lake ◽  
Subglacial Environment ◽  
Ice Surface ◽  
Ice Stream ◽  
Slow Moving ◽  
Lake Drainage ◽  
Subglacial Lakes

Abstract. The growth and drainage of active subglacial lakes in Antarctica has previously been inferred from analysis of ice surface altimetry data. We use a subglacial hydrology model applied to a synthetic Antarctic ice stream to examine internal controls on the filling and drainage of subglacial lakes. Our model outputs suggest that the highly constricted subglacial environment of our idealized ice stream, combined with relatively high rates of water flow funneled from a large catchment, can combine to create a system exhibiting slow-moving pressure waves. Over a period of years, the accumulation of water in the ice stream onset region results in a buildup of pressure creating temporary channels, which then evacuate the excess water. This increased flux of water beneath the ice stream drives lake growth. As the water body builds up, it steepens the hydraulic gradient out of the overdeepened lake basin and allows greater flux. Eventually this flux is large enough to melt channels that cause the lake to drain. Lake drainage also depends on the internal hydrological development in the wider system and therefore does not directly correspond to a particular water volume or depth. This creates a highly temporally and spatially variable system, which is of interest for assessing the importance of subglacial lakes in ice stream hydrology and dynamics.

scholarly journals Filling and drainage of a subglacial lake beneath the Flade Isblink ice cap, northeast Greenland

2022 ◽  
Author(s):  
Qi Liang ◽  
Wanxin Xiao ◽  
Ian Howat ◽  
Xiao Cheng ◽  
Fengming Hui ◽  
...  
Keyword(s):  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Aquifer Storage ◽  
Subglacial Lake ◽  
Ice Cap ◽  
Lake Volume ◽  
Basin Surface ◽  
Multi Temporal ◽  
Lake Drainage ◽  
Subglacial Lakes

Abstract. The generation, transport, storage and drainage of meltwater beneath the ice sheet play important roles in the Greenland ice sheet (GrIS) system. Active subglacial lakes, common features in Antarctica, have recently been detected beneath GrIS and may impact ice sheet hydrology. Despite their potential importance, few repeat subglacial lake filling and drainage events have been identified under Greenland Ice Sheet. Here we examine the surface elevation change of a collapse basin at the Flade Isblink ice cap, northeast Greenland, which formed due to sudden subglacial lake drainage in 2011. We estimate the subglacial lake volume evolution using multi-temporal ArcticDEM data and ICESat-2 altimetry data acquired between 2012 and 2021. Our long-term observations show that the subglacial lake was continuously filled by surface meltwater, with basin surface rising by up to 55 m during 2012–2021 and we estimate 138.2 × 106 m3 of meltwater was transported into the subglacial lake between 2012 and 2017. A second rapid drainage event occurred in late August 2019, which induced an abrupt ice dynamic response. Comparison between the two drainage events shows that the 2019 drainage released much less water than the 2011 event. We conclude that multiple factors, e.g., the volume of water stored in the subglacial lake and bedrock relief, regulate the episodic filling and drainage of the lake. By comparing the surface meltwater production and the subglacial lake volume change, we find only ~64 % of the surface meltwater successfully descended to the bed, suggesting potential processes such as meltwater refreezing and firn aquifer storage, need to be further quantified.

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 Brief communication: Subglacial lake drainage beneath Isunguata Sermia, West Greenland: geomorphic and ice dynamic effects

2019 ◽  
Vol 13 (10) ◽  
pp. 2789-2796 ◽  
Author(s):  
Stephen J. Livingstone ◽  
Andrew J. Sole ◽  
Robert D. Storrar ◽  
Devin Harrison ◽  
Neil Ross ◽  
...  
Keyword(s):  
Water Bodies ◽  
Lateral Margin ◽  
Dynamic Effects ◽  
Ice Flow ◽  
West Greenland ◽  
Subglacial Lake ◽  
Ice Surface ◽  
Geophysical Investigations ◽  
Lake Drainage ◽  
Subglacial Lakes

Abstract. We report three active subglacial lakes within 2 km of the lateral margin of Isunguata Sermia, West Greenland, identified by differencing time-stamped ArcticDEM strips. Each lake underwent one drainage–refill event between 2009 and 2017, with two lakes draining in < 1 month in August 2014 and August 2015. The 2015 drainage caused a ∼ 1-month down-glacier slowdown in ice flow and flooded the foreland, aggrading the proglacial channel by 8 m. The proglacial flooding confirms the ice-surface elevation anomalies as subglacial water bodies and demonstrates how their drainage can significantly modify proglacial environments. These subglacial lakes offer accessible targets for geophysical investigations and exploration.

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 Modeling Antarctic subglacial lake filling and drainage cycles

2015 ◽  
Vol 9 (6) ◽  
pp. 6545-6579
Author(s):  
C. F. Dow ◽  
M. A. Werder ◽  
S. Nowicki ◽  
R. T. Walker
Keyword(s):  
High Water ◽  
Water Volume ◽  
Lake Basin ◽  
Subglacial Lake ◽  
Subglacial Environment ◽  
Ice Surface ◽  
Ice Stream ◽  
Drainage Channels ◽  
Lake Drainage ◽  
Subglacial Lakes

Abstract. The growth and drainage of active subglacial lakes in Antarctica has previously been inferred from analysis of ice surface altimetry data. We use a subglacial hydrology model applied to a synthetic Antarctic ice stream to determine internal controls on the filling and drainage of subglacial lakes and their impact on ice stream dynamics. Our model outputs suggest that the highly constricted subglacial environment of the ice stream, combined with relatively high rates of water flow funneled from large catchments, can combine to create a system exhibiting slow-moving pressure waves. Over a period of years, the accumulation of water in the ice stream onset region results in a buildup of pressure creating temporary channels, which then evacuate the excess water. This increased flux of water through the ice stream drives lake growth. As the water body builds up, it too steepens the hydraulic gradient and allows greater flux out of the overdeepened lake basin. Eventually this flux is large enough to create channels that cause the lake to drain. Due to the presence of the channels, the drainage of the lake causes high water pressures around 50 km downstream of the lake rather than immediately in the vicinity of the overdeepening. Following lake drainage, channels again shut down. Lake drainage depends on the internal hydrological development in the wider system and therefore does not directly correspond to a particular water volume or depth. This creates a highly temporally and spatially variable system, which is of interest for assessing the importance of subglacial lakes in ice stream hydrology and dynamics.

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

2017 ◽  
Vol 11 (1) ◽  
pp. 451-467 ◽  
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 (TWG). Much of the drainage happened in less than 6 months, with an apparent connection between three lakes spanning more than 130 km. Hydro-potential 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. This shows that there are important limitations in the ability of hydro-potential 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.

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