An inventory of Antarctic sub-glacial lakes

Siegert, Martín J.; Dowdeswell, Julian A.; Gorman, Michael R.; McIntyre, Neil

doi:10.1017/s0954102096000405

Cited by 121 publications

(73 citation statements)

References 12 publications

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“…Around 50% of the Antarctic ice-sheet bed is known to be wet, as is evident from hundreds of Antarctic subglacial lakes that have been detected using ice-penetrating radar (Siegert et al 1996(Siegert et al , 2005Wright & Siegert 2011. Many of these lakes are connected hydrologically over large (hundreds of kilometres) distances (Wingham et al 2006;Smith et al 2009), some have been identified at the onset of fast flow (Siegert & Bamber 2000;Bell et al 2007) and water issued from a few of them has been shown to influence ice-sheet flow (Stearns et al 2008;Siegfried et al 2016).…”

Section: Water Beneath the Ice Sheetmentioning

confidence: 99%

“…Indeed, where RES data are suitable for synthetic aperture radar (SAR) processing, the specularity content of the bed echoes has been used to directly measure discrete subglacial channels and distinguish them from distributed canals (Schroeder et al 2013). RES is also able to detect deep-water (>10 m) subglacial lakes (Siegert et al 1996(Siegert et al , 2005Wright & Siegert 2012), although not normally 'active subglacial lakes' (Siegert et al 2014).…”

Section: Hydrological and Mechanical Conditions At The Ice-sheet Bedmentioning

confidence: 99%

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Antarctic subglacial groundwater: a concept paper on its measurement and potential influence on ice flow

Siegert

Kulessa

Bougamont

et al. 2017

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Is groundwater abundant in Antarctica and does it modulate ice flow? Answering this question matters because ice streams flow by gliding over a wet substrate of till. Water fed to icestream beds thus influences ice-sheet dynamics and, potentially, sea-level rise. It is recognized that both till and the sedimentary basins from which it originates are porous and could host a reservoir of mobile groundwater that interacts with the subglacial interfacial system. According to recent numerical modelling, up to half of all water available for basal lubrication, and time lags between hydrological forcing and ice-sheet response as long as millennia, may have been overlooked in models of ice flow. Here, we review evidence in support of Antarctic groundwater and propose how it can be measured to ascertain the extent to which it modulates ice flow. We present new seismoelectric soundings of subglacial till, and magnetotelluric and transient electromagnetic forward models of subglacial groundwater reservoirs. We demonstrate that multifaceted and integrated geophysical datasets can detect, delineate and quantify the groundwater contents of subglacial sedimentary basins and, potentially, monitor groundwater exchange rates between subglacial till layers. The paper thus describes a new area of glaciological investigation and how it should progress in future.Gold Open Access: This article is published under the terms of the CC-BY 3.0 license. Water beneath the ice sheetAntarctic ice-sheet flow is fundamentally affected by water at the bed, as it reduces basal friction to encourage sliding and weakens till to enable bed deformation. Subglacial hydrology -the flow of water beneath the ice -is therefore a key element of the ice-sheet system. Studies to date on subglacial hydrology, and its impact on ice flow, have concentrated on water at or very near to the bed of the ice sheet.Basal water modulation of ice flow can be achieved in a number of ways. Over an impermeable bed, water can flow through channels cut either downwards into the substrate or upwards into the ice. Enhanced basal water pressures may occur where the channels and their linkages are distributed, increasing overriding ice flow through a reduction in the substrate's effective pressure. Conversely, where a well-organized channel system is formed, water pressures are lower and the hydrological effect on ice flow is reduced. If the ice stream rests on permeable subglacial till, its strength can affect ice flow as controlled by porewater pressures. High pressures lead to a reduction in material strength by pushing till grains apart, reducing bed friction and thus

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Section: Water Beneath the Ice Sheetmentioning

confidence: 99%

Section: Hydrological and Mechanical Conditions At The Ice-sheet Bedmentioning

confidence: 99%

Antarctic subglacial groundwater: a concept paper on its measurement and potential influence on ice flow

Siegert

Kulessa

Bougamont

et al. 2017

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“…In their analysis of airborne radar surveys of Antarctica, Siegert et al (34) found evidence for at least 77 subglacial lakes, one of which has subsequently proved to be only a few kilometers from the South Pole Station (D. Blankenship and D. Morse, unpublished results). The idea of collecting water, ice, and sediments from the South Pole subglacial lake has both advantages and disadvantages compared with sampling Lake Vostok.…”

Section: Hcoomentioning

confidence: 99%

A habitat for psychrophiles in deep Antarctic ice

2000

Proc. Natl. Acad. Sci. U.S.A.

292

202

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Microbes, some of which may be viable, have been found in ice cores drilled at Vostok Station at depths down to Ϸ3,600 m, close to the surface of the huge subglacial Lake Vostok. Two types of ice have been found. The upper 3,500 m comprises glacial ice containing traces of nutrients of aeolian origin including sulfuric acid, nitric acid, methanosulfonic acid (MSA), formic acid, sea salts, and mineral grains. Ice below Ϸ3,500 m comprises refrozen water from Lake Vostok, accreted to the bottom of the glacial ice. Nutrients in the accretion ice include salts and dissolved organic carbon. There is great interest in searching for living microbes and especially for new species in deepest Antarctic ice. I propose a habitat consisting of interconnected liquid veins along three-grain boundaries in ice in which psychrophilic bacteria can move and obtain energy and carbon from ions in solution. In the accretion ice, with an age of a few 10 4 years and a temperature a few degrees below freezing, the carbon and energy sources in the veins can maintain significant numbers of cells per cubic centimeter that are metabolizing but not multiplying. In the 4 ؋ 10 5 -year-old colder glacial ice, at least 1 cell per cm 3 in acid veins can be maintained. With fluorescence microscopy tuned to detect NADH in live organisms, motile bacteria could be detected by direct scanning of the veins in ice samples.

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“…Three different lakes sizes are used, based on typical sizes of subglacial lakes found in Antarctica (Siegert et al, 1996;Siegert and Kwok, 2000). The lakes are all elliptical in shape, with major and minor axes defined in Table 2.…”

Section: Computational Domainmentioning

confidence: 99%

“…Subglacial lakes are typically located either in the ice-sheet interior, close to ice divides where surface slopes are low and ice is thick, or in areas of higher ice velocity where internal ice deformation and sliding add to geothermal energy to produce melting at the base (Siegert et al, 1996;Dowdeswell and Siegert, 1999).…”

Section: Introductionmentioning

confidence: 99%

The influence of a model subglacial lake on ice dynamics and internal layering

et al. 2016

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Abstract.As ice flows over a subglacial lake, the drop in bed resistance leads to an increase in ice velocities and a draw down of isochrones and cold ice. The ice surface flattens as it adjusts to the lack of resisting forces at the base. The rapid transition in velocity induces changes in ice viscosity and releases deformation energy that can raise the temperature locally. Recent studies of Antarctic subglacial lakes indicate that many lakes experience very fast and possibly episodic drainage, during which the lake size is rapidly reduced as water flows out. Questions that arise are what effect this would have on internal layers within the ice and whether such past drainage events could be inferred from isochrone structures downstream.Here, we study the effect of a subglacial lake on ice dynamics as well as the influence that such short timescale drainage would have on the internal layers of the ice. To this end, we use a full Stokes, polythermal ice flow model. An enthalpy-gradient method is used to account for the evolution of temperature and water content within the ice.We find that a rapid transition between slow-moving ice outside the lake, and full sliding over the lake, can release considerable amounts of deformational energy, with the potential to form a temperate layer at depth in the transition zone. In addition, we provide an explanation for a characteristic surface feature commonly seen at the edges of subglacial lakes, a hummocky surface depression in the transition zone between little to full sliding. We also conclude that rapid changes in the horizontal extent of subglacial lakes and slippery patches, compared to the average ice column velocity, can create a traveling wave at depth within the isochrone structure that transfers downstream with the advection of ice, thus indicating the possibility of detecting past drainage events with ice penetrating radar.

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An inventory of Antarctic sub-glacial lakes

Cited by 121 publications

References 12 publications

Antarctic subglacial groundwater: a concept paper on its measurement and potential influence on ice flow

Antarctic subglacial groundwater: a concept paper on its measurement and potential influence on ice flow

A habitat for psychrophiles in deep Antarctic ice

The influence of a model subglacial lake on ice dynamics and internal layering

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