scholarly journals Dynamic flows create potentially habitable conditions in Antarctic subglacial lakes

2021 ◽  
Vol 7 (8) ◽  
pp. eabc3972
Author(s):  
Louis-Alexandre Couston ◽  
Martin Siegert
Keyword(s):  
Bulk Water ◽  
Water Sampling ◽  
Stable Layer ◽  
Microbial Life ◽  
Subglacial Lake ◽  
Physical Conditions ◽  
Dynamic Flows ◽  
Subglacial Lakes ◽  
Ice Water ◽  
The Antarctic

Trapped beneath the Antarctic ice sheet lie over 400 subglacial lakes, which are considered to be extreme, isolated, yet viable habitats for microbial life. The physical conditions within subglacial lakes are critical to evaluating how and where life may best exist. Here, we propose that Earth’s geothermal flux provides efficient stirring of Antarctic subglacial lake water. We demonstrate that most lakes are in a regime of vigorous turbulent vertical convection, enabling suspension of spherical particulates with diameters up to 36 micrometers. Thus, dynamic conditions support efficient mixing of nutrient- and oxygen-enriched meltwater derived from the overlying ice, which is essential for biome support within the water column. We caution that accreted ice analysis cannot always be used as a proxy for water sampling of lakes beneath a thin (<3.166 kilometers) ice cover, because a stable layer isolates the well-mixed bulk water from the ice-water interface where freezing may occur.

scholarly journals Antarctic subglacial lake exploration: first results and future plans

2016 ◽  
Vol 374 (2059) ◽  
pp. 20140466 ◽  
Author(s):  
Martin J. Siegert ◽  
John C. Priscu ◽  
Irina A. Alekhina ◽  
Jemma L. Wadham ◽  
W. Berry Lyons
Keyword(s):  
Lake Water ◽  
Ice Core ◽  
Hot Water ◽  
Microbial Life ◽  
Lake Vostok ◽  
Subglacial Lake ◽  
Coastal Margin ◽  
First Results ◽  
Scientific Results ◽  
Subglacial Lakes

After more than a decade of planning, three attempts were made in 2012–2013 to access, measure in situ properties and directly sample subglacial Antarctic lake environments. First, Russian scientists drilled into the top of Lake Vostok, allowing lake water to infiltrate, and freeze within, the lower part of the ice-core borehole, from which further coring would recover a frozen sample of surface lake water. Second, UK engineers tried unsuccessfully to deploy a clean-access hot-water drill, to sample the water column and sediments of subglacial Lake Ellsworth. Third, a US mission successfully drilled cleanly into subglacial Lake Whillans, a shallow hydraulically active lake at the coastal margin of West Antarctica, obtaining samples that would later be used to prove the existence of microbial life and active biogeochemical cycling beneath the ice sheet. This article summarizes the results of these programmes in terms of the scientific results obtained, the operational knowledge gained and the engineering challenges revealed, to collate what is known about Antarctic subglacial environments and how to explore them in future. While results from Lake Whillans testify to subglacial lakes as being viable biological habitats, the engineering challenges to explore deeper more isolated lakes where unique microorganisms and climate records may be found, as exemplified in the Lake Ellsworth and Vostok missions, are considerable. Through international cooperation, and by using equipment and knowledge of the existing subglacial lake exploration programmes, it is possible that such environments could be explored thoroughly, and at numerous sites, in the near future.

scholarly journals Potential subglacial lake locations and meltwater drainage pathways beneath the Antarctic and Greenland ice sheets

2013 ◽  
Vol 7 (6) ◽  
pp. 1721-1740 ◽  
Author(s):  
S. J. Livingstone ◽  
C. D. Clark ◽  
J. Woodward ◽  
J. Kingslake
Keyword(s):  
Ice Sheets ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Simplified Approach ◽  
Subglacial Lake ◽  
Ice Stream ◽  
Geophysical Surveys ◽  
Subglacial Lakes ◽  
The Antarctic ◽  
Subglacial Drainage

Abstract. We use the Shreve hydraulic potential equation as a simplified approach to investigate potential subglacial lake locations and meltwater drainage pathways beneath the Antarctic and Greenland ice sheets. We validate the method by demonstrating its ability to recall the locations of >60% of the known subglacial lakes beneath the Antarctic Ice Sheet. This is despite uncertainty in the ice-sheet bed elevation and our simplified modelling approach. However, we predict many more lakes than are observed. Hence we suggest that thousands of subglacial lakes remain to be found. Applying our technique to the Greenland Ice Sheet, where very few subglacial lakes have so far been observed, recalls 1607 potential lake locations, covering 1.2% of the bed. Our results will therefore provide suitable targets for geophysical surveys aimed at identifying lakes beneath Greenland. We also apply the technique to modelled past ice-sheet configurations and find that during deglaciation both ice sheets likely had more subglacial lakes at their beds. These lakes, inherited from past ice-sheet configurations, would not form under current surface conditions, but are able to persist, suggesting a retreating ice-sheet will have many more subglacial lakes than advancing ones. We also investigate subglacial drainage pathways of the present-day and former Greenland and Antarctic ice sheets. Key sectors of the ice sheets, such as the Siple Coast (Antarctica) and NE Greenland Ice Stream system, are suggested to have been susceptible to subglacial drainage switching. We discuss how our results impact our understanding of meltwater drainage, basal lubrication and ice-stream formation.

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.

Hard thermal turbulence in Antarctic Subglacial Lakes

2020 ◽  
Author(s):  
Martin Siegert ◽  
Louis-Alexandre Couston
Keyword(s):  
Water Depth ◽  
Temperature Fluctuations ◽  
Ice Cover ◽  
Stable Layer ◽  
Convective Turbulence ◽  
Physical Conditions ◽  
Thermal Turbulence ◽  
Melt Water ◽  
Subglacial Lakes ◽  
Geothermal Flux

&lt;p&gt;Over 250 stable and isolated subglacial lakes exist at and close to the ice-sheet center in Antarctica. The physical conditions within subglacial lakes, and the differences between distinct lake settings, are critical to evaluating how and where life may best exist. Here, we demonstrate that upward heating by Earth&amp;#8217;s geothermal flux provides efficient stirring of Antarctic subglacial lakes&amp;#8217; water, in a variety of ways related to their water depth, ice overburden and ceiling slope. We show that most lakes are in a regime of hard convective turbulence, enabling efficient mixing of nutrient- and oxygen-enriched top melt-water, which is essential for biome formation. Lakes beneath a thin (about less than 3 km) ice cover and lakes with a thick (more than 3 km) ice cover experience similarly-large velocities, but the latter have significantly larger temperature fluctuations and have a stable layer up to several tens of meters thick adjacent to the ice. We discuss the implications of hydrological conditions on the concentration of particulates in the water column.&lt;/p&gt;

scholarly journals Assessing the subglacial lake coverage of Antarctica

2016 ◽  
Vol 57 (72) ◽  
pp. 109-117 ◽  
Author(s):  
Sebastian Goeller ◽  
Daniel Steinhage ◽  
Malte Thoma ◽  
Klaus Grosfeld
Keyword(s):  
Remote Sensing ◽  
East Antarctica ◽  
Ice Dynamics ◽  
Potential Equation ◽  
Subglacial Lake ◽  
Covered Area ◽  
Radio Echo Sounding ◽  
Dronning Maud Land ◽  
Subglacial Lakes ◽  
The Antarctic

ABSTRACTLakes beneath the Antarctic Ice Sheet are known to decrease traction at the ice base and therefore can have a great impact on ice dynamics. However, the total extent of Antarctic subglacial lakes is still unknown. We address this issue by combining modeling and remote-sensing strategies to predict potential lake locations using the general hydraulic potential equation. We are able to reproduce the majority of known lakes, as well as predict the existence of many new and so far undetected potential lakes. To validate our predictions, we analyzed ice-penetrating radar profiles from radio-echo sounding flights acquired over 1994–2013 in Dronning Maud Land, East Antarctica, and this led to the identification of 31 new subglacial lakes. Based on these findings, we estimate the total number of Antarctic subglacial lakes to be ~1300, a factor of three higher than the total number of lakes discovered to date. We estimate that only ~30% of all Antarctic subglacial lakes and ~65% of the total estimated lake-covered area have been discovered, and that lakes account for 0.6% of the Antarctic ice/bed interface.

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 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.

Reviewing the origin of subglacial Lake Vostok and its sensitivity to ice sheet changes

2005 ◽  
Vol 29 (2) ◽  
pp. 156-170 ◽  
Author(s):  
Martin J. Siegert
Keyword(s):  
Ice Sheet ◽  
Extreme Environment ◽  
Ice Cover ◽  
Ice Growth ◽  
Lake Vostok ◽  
Subglacial Lake ◽  
Ice Surface ◽  
Ice Flows ◽  
Subglacial Lakes ◽  
Ice Water

The history of Lake Vostok, the huge East Antarctic subglacial lake, is critical to the unique biota expected in this extreme environment. One theory is that the lake existed prior to the mid-Miocene glaciation of the continent at around 15 million years ago, survived the subsequent period of ice growth intact, and then remained relatively stable beneath its thick ice cover to the present day. The alternative is that the lake was formed by subglacial water flow into an existing and/or glacially eroded trough after the ice sheet reached its present configuration. Here, the onset of persistent ice cover in Antarctica is reviewed and a simple model for continental ice growth discussed. This information is used to argue against the preglacial origin of subglacial lakes. Lake Vostok is large because ice flows essentially perpendicular to the trough’s long axis, permitting the slopes of the ice surface and the ice-water interface to be low. During the onset of glaciation ice flow across Lake Vostok would have been more akin to flow across an ice marginal trough such as the Astrolabe Subglacial Basin, which holds the thickest ice in Antarctica: 4776 m where the bed is over 2 km below the sea level. Hence, regardless of whether Lake Vostok was a lake prior to glaciation, its trough is likely to have been occupied by grounded ice during the period of ice growth. Although the lake is stable today, its size and extent will be affected by ice sheet changes that occur over glacial-interglacial cycles. Such changes are reviewed and the potential consequences for the lake’s volume are discussed.

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

2019 ◽  
Vol 13 (7) ◽  
pp. 1959-1981 ◽  
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 507 m wide and 43 m deep on average, the channels offshore of present-day Pine Island and Thwaites glaciers are approximately twice as deep, 3 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 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.

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