Increased flow speed on a large East Antarctic outlet glacier caused by subglacial floods

Stearns, L. A.; Smith, B. E.; Hamilton, G. S.

doi:10.1038/ngeo356

Cited by 278 publications

(306 citation statements)

References 23 publications

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“…At peak discharge, the flux of freshwater was two orders of magnitude above the background flow, implying an approximate fourfold increase in the mean melt rate. Stearns et al (2008) observed the discharge of a subglacial lake beneath the upper part of Byrd Glacier. Although the lake was some distance from the grounding line, they inferred from the increase in flow speed of the glacier that the water drained toward the ice shelf.…”

Section: B Whillans Ice Streammentioning

confidence: 99%

“…Laser-altimeter data have revealed an active hydrological system beneath the Antarctic ice sheet with water moving from one subglacial lake to another ) and periodically draining across grounding lines (Fricker et al 2007;Stearns et al 2008). Surface meltwater is known to drain to the bed of the Greenland Ice Sheet, imparting a seasonal variability to the motion of ice in the ablation zone (Zwally et al 2002;Das et al 2008;Joughin et al 2008), and at least some of this meltwater eventually reaches the grounding lines of the tidewater glaciers and upwells at the calving fronts (Chu et al 2009).…”

mentioning

confidence: 99%

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Convection-Driven Melting near the Grounding Lines of Ice Shelves and Tidewater Glaciers

Jenkins

2011

Journal of Physical Oceanography

425

732

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Subglacial meltwater draining along the bed of fast-flowing, marine-terminating glaciers emerges at the grounding line, where the ice either goes afloat to form an ice shelf or terminates in a calving face. The input of freshwater to the ocean provides a source of buoyancy and drives convective motion alongside the ice-ocean interface. This process is modeled using the theory of buoyant plumes that has previously been applied to the study of the larger-scale circulation beneath ice shelves. The plume grows through entrainment of ocean waters, and the heat brought into the plume as a result drives melting at the ice-ocean interface. The equations are nondimensionalized by using scales appropriate for the region where the subglacial drainage, rather than the subsequent addition of meltwater, supplies the majority of the buoyancy forcing. It is found that the melt rate within this region can be approximated reasonably well by a function that is linear in ocean temperature, has a cube root dependence on the flux of subglacial meltwater, and has a complex dependency on the slope of the ice-ocean interface. The model is used to investigate variability in melting induced by changes in both ocean temperature and subglacial discharge for a number of realistic examples of ice shelves and tidewater glaciers. The results show how warming ocean waters and increasing subglacial drainage both generate increases in melting near the grounding line.

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Section: B Whillans Ice Streammentioning

confidence: 99%

mentioning

confidence: 99%

Convection-Driven Melting near the Grounding Lines of Ice Shelves and Tidewater Glaciers

Jenkins

2011

Journal of Physical Oceanography

425

732

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“…Boulton, Dobbie, & Zatsepin, 2001;Schoof, 2010;Stearns, Smith, & Hamilton, 2008). Given the increase in meltwater production as a result of increased warming in polar regions (e.g.…”

Section: Introductionmentioning

confidence: 99%

A map of large Canadian eskers from Landsat satellite imagery

2013

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Meltwater drainage systems beneath ice sheets are a poorly understood, yet fundamentally important environment for understanding glacier dynamics, which are strongly influenced by the nature and quantity of meltwater entering the subglacial system. Contemporary sub-ice sheet meltwater drainage systems are notoriously difficult to study, but we can utilise exposed beds of palaeo-ice sheets to further our understanding of subglacial drainage. In particular, eskers record deposition in glacial drainage channels and are widespread on the exposed beds of former ice sheets. This paper presents a 1:5,000,000 scale map of .20,000 large eskers (typically . 2 km long) deposited by the Laurentide Ice Sheet (LIS), mapped from Landsat imagery of Canada, in order to establish a dataset suitable for analysis of esker morphometry and drainage patterns at the ice sheet scale. Comparisons between eskers mapped from Landsat imagery and aerial photographs indicate that, in most areas, approximately 75% of eskers are detected using Landsat. The data presented in this map build on and extend previous work in providing a consistent map of an unprecedented sample of eskers for quantitative analysis. It offers an alternative perspective on the problems surrounding ice-sheet meltwater drainage and can be used for: (i) detailed investigations of esker morphometry and distribution from a large sample size; (ii), testing of numerical models of meltwater drainage routing that predict esker characteristics (e.g. channel spacing, sinuosity), (iii) assessment of the factors that control esker location and formation; and (iv), a refined understanding of ice margin configurations during retreat of the LIS.

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“…The effect the draining water will have on isochrone layers will depend on the state of the drainage system and how the water is transported downstream (Stearns et al, 2008) but will likely be limited by the swiftness of the ice response compared to the time needed to perturb isochrone layers considerably.…”

Section: Model Experimentsmentioning

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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Increased flow speed on a large East Antarctic outlet glacier caused by subglacial floods

Cited by 278 publications

References 23 publications

Convection-Driven Melting near the Grounding Lines of Ice Shelves and Tidewater Glaciers

Convection-Driven Melting near the Grounding Lines of Ice Shelves and Tidewater Glaciers

A map of large Canadian eskers from Landsat satellite imagery

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

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