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 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 Modeling oscillations in connected glacial lakes

2019 ◽  
Vol 65 (253) ◽  
pp. 745-758 ◽  
Author(s):  
Aaron G. Stubblefield ◽  
Timothy T. Creyts ◽  
Jonathan Kingslake ◽  
Marc Spiegelman
Keyword(s):  
Complex Dynamics ◽  
Equation Model ◽  
Qualitative Behavior ◽  
Glacial Lakes ◽  
West Antarctica ◽  
Ice Streams ◽  
Mountain Glaciers ◽  
Lake Model ◽  
Dependent Model ◽  
Subglacial Lakes

AbstractMountain glaciers and ice sheets often host marginal and subglacial lakes that are hydraulically connected through subglacial drainage systems. These lakes exhibit complex dynamics that have been the subject of models for decades. Here we introduce and analyze a model for the evolution of glacial lakes connected by subglacial channels. Subglacial channel equations are supplied with effective pressure boundary conditions that are determined by a simple lake model. While the model can describe an arbitrary number of lakes, we solve it numerically with a finite element method for the case of two connected lakes. We examine the effect of relative lake size and spacing on the oscillations. Complex oscillations in the downstream lake are driven by discharge out of the upstream lake. These include multi-peaked and anti-phase filling–draining events. Similar filling–draining cycles have been observed on the Kennicott Glacier in Alaska and at the confluence of the Whillans and Mercer ice streams in West Antarctica. We further construct a simplified ordinary differential equation model that displays the same qualitative behavior as the full, spatially-dependent model. We analyze this model using dynamical systems theory to explain the appearance of filling–draining cycles as the meltwater supply varies.

scholarly journals Water Movement At The Base Of Ice Sheets

1979 ◽  
Vol 23 (89) ◽  
pp. 410
Author(s):  
I. M. Whillans
Keyword(s):  
Heat Transfer ◽  
Water Movement ◽  
Ice Sheets ◽  
Differential Heat ◽  
Subglacial Lake ◽  
Basal Sliding ◽  
Subglacial Lakes

Abstract Flat-surfaced subglacial lakes, such as those discovered by Oswald (1975), can form where basal sliding velocities are low. As the glacier moves onto a subglacial lake, its underside retains the shape of the vertical relief at the lake edge. Differential heat transfer from the lake into high and low points in the interface flattens the surface by extra melting of the downward projections or freezing in the high areas. A time of the order of 103 years is required to flatten the fluting, and the down-glacier part of a subglacial lake can be flat-surfaced if the glacier takes longer than some 103 years to traverse the lake. Such a slow traverse time is expected near ice-drainage divides, and it is there that flat-surfaced lakes were discovered by radar sounding.

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 Synthesizing multiple remote-sensing techniques for subglacial hydrologic mapping: application to a lake system beneath MacAyeal Ice Stream, West Antarctica

2010 ◽  
Vol 56 (196) ◽  
pp. 187-199 ◽  
Author(s):  
Helen Amanda Fricker ◽  
Ted Scambos ◽  
Sasha Carter ◽  
Curt Davis ◽  
Terry Haran ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Water Movement ◽  
Satellite Image ◽  
West Antarctica ◽  
Basal Resistance ◽  
Ice Stream ◽  
Radio Echo Sounding ◽  
Satellite Radar ◽  
Remote Sensing Techniques ◽  
Subglacial Lakes

AbstractWe present an analysis of the active hydrologic system of MacAyeal Ice Stream (MacIS), West Antarctica, from a synthesis of multiple remote-sensing techniques: satellite laser altimetry; satellite image differencing; and hydrologic potential mapping (using a satellite-derived DEM and a bedrock DEM from airborne radio-echo sounding). Combining these techniques augments the information provided by each one individually, and allows us to develop a protocol for studying subglacial hydrologic systems in a holistic manner. Our study reveals five large active subglacial lakes under MacIS, the largest of which undergoes volume changes of at least 1.0 km3. We discuss the hydrologic properties of this system and present evidence for links between the lakes. At least three of the lakes are co-located with sticky spots, i.e. regions of high local basal shear stress. We also find evidence for surface elevation changes due to ice-dynamic effects (not just water movement) caused by changes in basal resistance. Lastly, we show that satellite radar altimetry is of limited use for monitoring lake activity on fast-flowing ice streams with surfaces that undulate on ∼10 km length scales.

scholarly journals Water Movement At The Base Of Ice Sheets

1979 ◽  
Vol 23 (89) ◽  
pp. 410-410
Author(s):  
I. M. Whillans
Keyword(s):  
Heat Transfer ◽  
Water Movement ◽  
Ice Sheets ◽  
Differential Heat ◽  
Subglacial Lake ◽  
Basal Sliding ◽  
Subglacial Lakes

AbstractFlat-surfaced subglacial lakes, such as those discovered by Oswald (1975), can form where basal sliding velocities are low. As the glacier moves onto a subglacial lake, its underside retains the shape of the vertical relief at the lake edge. Differential heat transfer from the lake into high and low points in the interface flattens the surface by extra melting of the downward projections or freezing in the high areas. A time of the order of 103 years is required to flatten the fluting, and the down-glacier part of a subglacial lake can be flat-surfaced if the glacier takes longer than some 103 years to traverse the lake. Such a slow traverse time is expected near ice-drainage divides, and it is there that flat-surfaced lakes were discovered by radar sounding.

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 Active subglacial lakes and channelized water flow beneath the Kamb Ice Stream

2016 ◽  
Vol 10 (6) ◽  
pp. 2971-2980 ◽  
Author(s):  
Byeong-Hoon Kim ◽  
Choon-Ki Lee ◽  
Ki-Weon Seo ◽  
Won Sang Lee ◽  
Ted Scambos
Keyword(s):  
Water System ◽  
Topographic Feature ◽  
Ice Shelf ◽  
Ice Streams ◽  
Ross Ice Shelf ◽  
Subglacial Lake ◽  
Ice Stream ◽  
Grounding Line ◽  
Subglacial Lakes ◽  
Kamb Ice Stream

Abstract. We identify two previously unknown subglacial lakes beneath the stagnated trunk of the Kamb Ice Stream (KIS). Rapid fill-drain hydrologic events over several months are inferred from surface height changes measured by CryoSat-2 altimetry and indicate that the lakes are probably connected by a subglacial drainage network, whose structure is inferred from the regional hydraulic potential and probably links the lakes. The sequential fill-drain behavior of the subglacial lakes and concurrent rapid thinning in a channel-like topographic feature near the grounding line implies that the subglacial water repeatedly flows from the region above the trunk to the KIS grounding line and out beneath the Ross Ice Shelf. Ice shelf elevation near the hypothesized outlet is observed to decrease slowly during the study period. Our finding supports a previously published conceptual model of the KIS shutdown stemming from a transition from distributed flow to well-drained channelized flow of subglacial water. However, a water-piracy hypothesis in which the KIS subglacial water system is being starved by drainage in adjacent ice streams is also supported by the fact that the degree of KIS trunk subglacial lake activity is relatively weaker than those of the upstream lakes.

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.

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