Greenland subglacial lakes detected by radar

Palmer, S. J.; Dowdeswell, Julian A.; Christoffersen, Poul; Young, D. A.; Blankenship, D. D.; Greenbaum, J. S.; Benham, Toby; Bamber, Jonathan; Siegert, Martín J.

doi:10.1002/2013gl058383

Cited by 78 publications

(91 citation statements)

References 40 publications

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“…However, subglacial water pressure varies spatially and temporally due to heterogeneities in the drainage system structure and water delivery, causing hydraulic gradients to evolve and even reverse on timescales ranging from diurnal to seasonal [58••, 59]. Under certain topographic conditions, meltwaters may also be stored in subglacial lakes [60], temporally delaying the routing of waters to the ice sheet margin if the lakes are connected to the wider ice sheet subglacial drainage system.…”

Section: Subglacial Meltwater Processesmentioning

confidence: 99%

Recent Advances in Our Understanding of the Role of Meltwater in the Greenland Ice Sheet System

Nienow

Sole

Slater

et al. 2017

Curr Clim Change Rep

100

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Purpose of the Review This review discusses the role that meltwater plays within the Greenland ice sheet system. The ice sheet's hydrology is important because it affects mass balance through its impact on meltwater runoff processes and ice dynamics. The review considers recent advances in our understanding of the storage and routing of water through the supraglacial, englacial, and subglacial components of the system and their implications for the ice sheet. Recent Findings There have been dramatic increases in surface meltwater generation and runoff since the early 1990s, both due to increased air temperatures and decreasing surface albedo. Processes in the subglacial drainage system have similarities to valley glaciers and in a warming climate, the efficiency of meltwater routing to the ice sheet margin is likely to increase. The behaviour of the subglacial drainage system appears to limit the impact of increased surface melt on annual rates of ice motion, in sections of the ice sheet that terminate on land, while the large volumes of meltwater routed subglacially deliver significant volumes of sediment and nutrients to downstream ecosystems. Summary Considerable advances have been made recently in our understanding of Greenland ice sheet hydrology and its wider influences. Nevertheless, critical gaps persist both in our understanding of hydrology-dynamics coupling, notably at tidewater glaciers, and in runoff processes which ensure that projecting Greenland's future mass balance remains challenging.

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Section: Subglacial Meltwater Processesmentioning

confidence: 99%

Recent Advances in Our Understanding of the Role of Meltwater in the Greenland Ice Sheet System

Nienow

Sole

Slater

et al. 2017

Curr Clim Change Rep

100

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“…A weaker contrast in basal traction inside and outside the lake, or a less pronounced switch in flow mode such as one might expect beneath an ice stream (Leysinger Vieli et al, 2007;Parrenin and Hindmarsh, 2007), decreases the amplitude of the dip and ridge features as can be witnessed in Fig. 5a, where surface profiles for simulations with different sliding coefficients and ice thickness are compared (n = 3).…”

Section: Model Experimentsmentioning

confidence: 88%

“…In addition, the large supply of surface meltwater to the base of the Greenland Ice Sheet through hydrofracturing means that the drainage networks in place are probably already highly efficient and, thus, capable of draining subglacial water effectively and preventing or limiting subglacial lake development (Palmer et al, 2013).…”

Section: E Gudlaugsson Et Al: the Influence Of A Subglacial Lake Onmentioning

confidence: 99%

“…In addition to the balance equations above, we solve a separate equation for the ice age (χ) to determine the influence of the lake on the isochrone structure (Hindmarsh et al, 2009;Parrenin et al, 2006;Parrenin and Hindmarsh, 2007;Leysinger Vieli et al, 2007):…”

Section: Age Equationmentioning

confidence: 99%

“…Nearly 400 subglacial lakes have been identified in Antarctica based on radar data and satellite measurements (Wright and Siegert, 2012), as well as at least two subglacial lakes in Greenland, all of which satisfy established criteria for identification of subglacial lakes (Palmer et al, 2013). 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%

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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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A model for subglacial flooding through a preexisting hydrological network during the rapid drainage of supraglacial lakes

Adhikari

Tsai

2015

JGR Earth Surface

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Key Points:• Accounting for preexisting water causes subglacial flooding to be faster • Prior to flooding, water flow direction reverses, causing surface subsidence • The model is compatible with continuum subglacial hydrological models Abstract Increasingly large numbers of supraglacial lakes form and drain every summer on the Greenland Ice Sheet. Some of these lakes drain rapidly within the timescale of a few hours, and the vertical discharge of water during these events may find a preexisting film of water potentially within a distributed drainage system of linked cavities. Here we present a model for subglacial flooding applied specifically to such circumstances. One of many interesting results we find is that water flows in from the far field prior to the arrival of flooding. We systematically evaluate the effect of initial ice/bed opening on the degree of perturbation to the subglacial system. Of particular importance, we find that floods propagate much faster and vertical displacements are much greater for larger openings. For 10 and 1 cm of initial opening, for example, floods travel about 68% and 50% farther than in the fully coupled ice/bed scenario after 2 h of drainage, respectively. For the same choices of initial opening, the elastostatic displacement at the injection point is about 1.39 and 1.26 times that of the fully coupled scenario. Using the framework with a preexisting water film results in avoiding the pressure singularity that is inherent to classical hydrofracture models, thus opening an avenue for integrating the likes of our model within continuum subglacial hydrological models. Furthermore, we foresee that the theory presented can be used to potentially infer subglacial hydrological conditions from surface observables.

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Greenland subglacial lakes detected by radar

Cited by 78 publications

References 40 publications

Recent Advances in Our Understanding of the Role of Meltwater in the Greenland Ice Sheet System

Recent Advances in Our Understanding of the Role of Meltwater in the Greenland Ice Sheet System

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

A model for subglacial flooding through a preexisting hydrological network during the rapid drainage of supraglacial lakes

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