scholarly journals Active lakes in Antarctica survive on a sedimentary substrate – Part 1: Theory

2015 ◽  
Vol 9 (2) ◽  
pp. 2053-2099 ◽  
Author(s):  
S. P. Carter ◽  
H. A. Fricker ◽  
M. R. Siegfried
Keyword(s):  
Process Model ◽  
Ice Sheet ◽  
Process Models ◽  
Ice Streams ◽  
Subglacial Lake ◽  
Lake Volume ◽  
Hydraulic Gradients ◽  
Lake Drainage ◽  
Subglacial Lakes ◽  
Lake Systems

Abstract. Over the past decade satellite observations have revealed that active subglacial lake systems are widespread under the Antarctic ice sheet, including the ice streams, yet we have insufficient understanding of the lake-drainage process to incorporate it into ice sheet models. Process models for drainage of ice-dammed lakes based on conventional "R-channels" incised into the base of the ice through melting are unable to reproduce the timing and magnitude of drainage from Antarctic subglacial lakes estimated from satellite altimetry given the low hydraulic gradients along which such lakes drain. We developed a process model in which channels are mechanically eroded into deformable subglacial sediment (till) instead ("T-channel"). When applied to the known lakes of the Whillans/Mercer system, the model successfully reproduced the key characteristics of estimated lake volume changes for the period 2003–2009. If our model is realistic, it implies that most active lakes are shallow and only exist in the presence of saturated sediment, explaining why they are difficult to detect with classical radar methods. It also implies that the lake-drainage process is sensitive to the composition and strength of the underlying till, suggesting that models could be improved with a realistic treatment of sediment – interfacial water exchange.

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 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 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.

scholarly journals Antarctic subglacial lakes drain through sediment-floored canals: theory and model testing on real and idealized domains

2017 ◽  
Vol 11 (1) ◽  
pp. 381-405 ◽  
Author(s):  
Sasha P. Carter ◽  
Helen A. Fricker ◽  
Matthew R. Siegfried
Keyword(s):  
Distributed System ◽  
Process Model ◽  
Ice Sheet ◽  
Drainage System ◽  
Drainage Water ◽  
Process Models ◽  
Altimeter Data ◽  
Laser Altimeter ◽  
Ice Stream ◽  
Subglacial Lakes

Abstract. Over the past decade, satellite observations of ice surface height have revealed that active subglacial lake systems are widespread under the Antarctic Ice Sheet, including the ice streams. For some of these systems, additional observations of ice-stream motion have shown that lake activity can affect ice-stream dynamics. Despite all this new information, we still have insufficient understanding of the lake-drainage process to incorporate it into ice-sheet models. Process models for drainage of ice-dammed lakes based on conventional R-channels incised into the base of the ice through melting are unable to reproduce the timing and magnitude of drainage from Antarctic subglacial lakes estimated from satellite altimetry given the low hydraulic gradients along which such lakes drain. We have developed an alternative process model, in which channels are mechanically eroded into the underlying deformable subglacial sediment. When applied to the known active lakes of the Whillans–Mercer ice-stream system, the model successfully reproduced both the inferred magnitudes and recurrence intervals of lake-volume changes, derived from Ice, Cloud and land Elevation Satellite (ICESat) laser altimeter data for the period 2003–2009. Water pressures in our model changed as the flood evolved: during drainage, water pressures initially increased as water flowed out of the lake primarily via a distributed system, then decreased as the channelized system grew, establishing a pressure gradient that drew water away from the distributed system. This evolution of the drainage system can result in the observed internal variability of ice flow over time. If we are correct that active subglacial lakes drain through canals in the sediment, this mechanism also implies that active lakes are typically located in regions underlain by thick subglacial sediment, which may explain why they are not readily observed using radio-echo-sounding techniques.

scholarly journals Antarctic subglacial lakes drain through sediment-floored canals: Theory and model testing on real and idealized domains

2016 ◽  
Author(s):  
Sasha P. Carter ◽  
Helen A. Fricker ◽  
Matthew R. Siegfried
Keyword(s):  
Distributed System ◽  
Process Model ◽  
Ice Sheet ◽  
Drainage System ◽  
Drainage Water ◽  
Process Models ◽  
Altimeter Data ◽  
Laser Altimeter ◽  
Ice Stream ◽  
Subglacial Lakes

Abstract. Over the past decade, satellite observations of ice surface height have revealed that active subglacial lake systems are widespread under the Antarctic ice sheet, including the ice streams. For some of these systems, additional observations of ice stream motion have shown that lake activity can affect ice-stream dynamics. Despite all this new information, we still have insufficient understanding of the lake-drainage process to incorporate it into ice sheet models. Process models for drainage of ice-dammed lakes based on conventional "R-channels" incised into the base of the ice through melting are unable to reproduce the timing and magnitude of drainage from Antarctic subglacial lakes estimated from satellite altimetry given the low hydraulic gradients along which such lakes drain. We have developed an alternative process model, in which channels are mechanically eroded into the underlying deformable subglacial sediment. When applied to the known active lakes of the Whillans/Mercer ice stream system, the model successfully reproduced both the inferred magnitudes and recurrence intervals of lake volume changes, derived from Ice, Cloud and land Elevation Satellite (ICESat) laser altimeter data for the period 2003–2009. Water pressures in our model changed as the flood evolved: during drainage, water pressures initially increased as water flowed out of the lake primarily via a distributed system, then decreased as the channelized system grew, establishing a pressure gradient that drew water away from the distributed system. This evolution of the drainage system can result in the observed internal variability of ice flow over time. If we are correct that active subglacial lakes drain through canals in the sediment, this mechanism also implies that active lakes are typically located in regions underlain by thick subglacial sediment, which may explain why they are not readily observed using radio-echo sounding techniques.

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 5 years of subglacial lake activity in the MacAyeal Ice Stream (Antarctica) catchment through assimilation of ICESat laser altimetry

2011 ◽  
Vol 57 (206) ◽  
pp. 1098-1112 ◽  
Author(s):  
Sasha P. Carter ◽  
Helen A. Fricker ◽  
Donald D. Blankenship ◽  
Jesse V. Johnson ◽  
William H. Lipscomb ◽  
...  
Keyword(s):  
Water Distribution ◽  
Large Scale ◽  
Transport Model ◽  
Laser Altimetry ◽  
Volume Changes ◽  
Ice Streams ◽  
Subglacial Lake ◽  
Lake Volume ◽  
Ice Stream ◽  
Subglacial Lakes

AbstractSubglacial lakes beneath Antarctica’s fast-moving ice streams are known to undergo ∼1 km3 volume changes on annual timescales. Focusing on the MacAyeal Ice Stream (MacIS) lake system, we create a simple model for the response of subglacial water distribution to lake discharge events through assimilation of lake volume changes estimated from Ice, Cloud and land Elevation Satellite (ICESat) laser altimetry. We construct a steady-state water transport model in which known subglacial lakes are treated as either sinks or sources depending on the ICESat-derived filling or draining rates. The modeled volume change rates of five large subglacial lakes in the downstream portion of MacIS are shown to be consistent with observed filling rates if the dynamics of all upstream lakes are considered. However, the variable filling rate of the northernmost lake suggests the presence of an undetected lake of similar size upstream. Overall, we show that, for this fast-flowing ice stream, most subglacial lakes receive >90% of their water from distant distributed sources throughout the catchment, and we confirm that water is transported from regions of net basal melt to regions of net basal freezing. Our study provides a geophysically based means of validating subglacial water models in Antarctica and is a potential way to parameterize subglacial lake discharge events in large-scale ice-sheet models where adequate data are available.

Repeat Subglacial Lake Drainage and Filling Beneath Thwaites Glacier, West-Antarctic Ice Sheet

2020 ◽  
Author(s):  
George Malczyk ◽  
Daniel Goldberg ◽  
Noel Gourmelen ◽  
Jan Wuite ◽  
Thomas Nagler
Keyword(s):  
Ice Sheet ◽  
Catchment Scale ◽  
Amundsen Sea ◽  
Ice Dynamics ◽  
Antarctic Ice Sheet ◽  
West Antarctic Ice Sheet ◽  
Subglacial Lake ◽  
West Antarctic ◽  
Lake Drainage ◽  
Subglacial Lakes

<p>Active subglacial lakes have been identified throughout Antarctica, offering a window into subglacial environments and into controls on ice dynamics. Between June 2013 and January 2014 a system of connected subglacial lakes drained in unison under the Thwaites glacier in the West Antarctic ice sheet, the first time that such a system has been observed in the Amundsen Sea Sector. Estimates based on catchment scale melt production suggested that lake drainages of this type should occur every 20 to 80 years. We collected elevations from January 2011 to December 2019 over the Thwaites lake region using the CryoSat-2 swath interferometric mode and ICEsat-2 land ice elevations, as well as ice velocity from the Sentinel-1 SAR mission since 2014. Using various elevation time series approaches, we obtain time dependent elevations over each lake. Results indicate that the upstream lakes undertake a second episode of drainage during mid-2017, only 3 years after the previous event, and that a new lake drained. Unlike the 2013-2014 episode, this new drainage episode contributed to filling one of the downstream lake with no evidence of further downstream activity. This new sub-glacial lake activity under Thwaites offer the possibility to explore lake connectivity, subglacial melt production and the interaction with ice dynamics.</p>

scholarly journals Subglacial water-sheet floods, drumlins and ice-sheet lobes

1999 ◽  
Vol 45 (150) ◽  
pp. 201-213 ◽  
Author(s):  
E.M. Shoemaker
Keyword(s):  
New York ◽  
Lake Michigan ◽  
New York State ◽  
Ice Sheet ◽  
Lake Ontario ◽  
High Water ◽  
Green Bay ◽  
Subglacial Lake ◽  
Western Lake ◽  
Subglacial Lakes

AbstractThe effect of subglacial lakes upon ice-sheet topography and the velocity patterns of subglacial water-sheet floods is investigated. A subglacial lake in the combined Michigan–Green Bay basin, Great Lakes, North America, leads to: (1) an ice-sheet lobe in the lee of Lake Michigan; (2) a change in orientations of flood velocities across the site of a supraglacial trough aligned closely with Green Bay, in agreement with drumlin orientations; (3) low water velocities in the lee of Lake Michigan where drumlins are absent; and (4) drumlinization occurring in regions of predicted high water velocities. The extraordinary divergence of drumlin orientations near Lake Ontario is explained by the presence of subglacial lakes in the Ontario and Erie basins, along with ice-sheet displacements of up to 30 km in eastern Lake Ontario. The megagrooves on the islands in western Lake Erie are likely to be the product of the late stage of a water-sheet flood when outflow from eastern Lake Ontario was dammed by displaced ice and instead flowed westward along the Erie basin. The Finger Lakes of northern New York state, northeastern U.S.A., occur in a region of likely ice-sheet grounding where water sheets became channelized. Green Bay and Grand Traverse Bay are probably the products of erosion along paths of strongly convergent water-sheet flow.

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.

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