Brief communication: Subglacial lake drainage beneath Isunguata Sermia, West Greenland: geomorphic and ice dynamic effects

Livingstone, Stephen J.; Sole, Andrew; Storrar, Robert D.; Harrison, Devin; Ross, Neil; Bowling, Jade

doi:10.5194/tc-13-2789-2019

Cited by 21 publications

(37 citation statements)

References 20 publications

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“…We hypothesize that this excess lowering could relate to a loss of subglacially stored water or sediment in this region following lake drainage. Hence, this pattern of persistent uplift downstream of the lake and surface lowering upstream could be explained by some combination of rerouting of the subglacial hydrological system (31) leading to increased water storage beneath the location of the GPS and/or the redistribution of subglacial sediment during rapid lake drainage (32).…”

Section: Discussionmentioning

confidence: 99%

Supraglacial lake drainage at a fast-flowing Greenlandic outlet glacier

Chudley

Christoffersen

Doyle³

et al. 2019

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

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Supraglacial lake drainage events influence Greenland Ice Sheet dynamics on hourly to interannual timescales. However, direct observations are rare, and, to date, no in situ studies exist from fast-flowing sectors of the ice sheet. Here, we present observations of a rapid lake drainage event at Store Glacier, west Greenland, in 2018. The drainage event transported 4.8 × 106m3of meltwater to the glacier bed in ∼5 h, reducing the lake to a third of its original volume. During drainage, the local ice surface rose by 0.55 m, and surface velocity increased from 2.0 m⋅d−1to 5.3 m⋅d−1. Dynamic responses were greatest ∼4 km downstream from the lake, which we interpret as an area of transient water storage constrained by basal topography. Drainage initiated, without any precursory trigger, when the lake expanded and reactivated a preexisting fracture that had been responsible for a drainage event 1 y earlier. Since formation, this fracture had advected ∼500 m from the lake’s deepest point, meaning the lake did not fully drain. Partial drainage events have previously been assumed to occur slowly via lake overtopping, with a comparatively small dynamic influence. In contrast, our findings show that partial drainage events can be caused by hydrofracture, producing new hydrological connections that continue to concentrate the supply of surface meltwater to the bed of the ice sheet throughout the melt season. Our findings therefore indicate that the quantity and resultant dynamic influence of rapid lake drainages are likely being underestimated.

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Section: Discussionmentioning

confidence: 99%

Supraglacial lake drainage at a fast-flowing Greenlandic outlet glacier

Chudley

Christoffersen

Doyle³

et al. 2019

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

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“…Significant water from surface melt may be stored in englacial reservoirs in the Greenland ice sheet and its outlet glaciers (Kendrick et al, 2018). The drainage of supraglacial lakes may recharge the subglacial aquifer (Willis et al, 2015), which in turn can significantly affect ice mass dynamics (Livingstone et al, 2019).…”

Section: Discussionmentioning

confidence: 99%

“…Glacial floods (jökulhlaups) are a dramatic phenomenon of some temperate and polythermal ice masses (Björnsson, 1992; Skidmore & Sharp, 1999); they play a role in the dynamics of some glaciers (Bingham et al, 2006; Björnsson, 1998; Livingstone et al, 2019; Magnússon et al, 2007) and are a significant hazard for human populations near glaciers (Björnsson, 2010). Two subglacial lakes maintained by volcanic heat under the Vatnajökull ice cap, southeastern Iceland, are the source of regular jökulhlaups in the Skaftá River (Figure 1).…”

Section: Introductionmentioning

confidence: 99%

Après Nous, le Déluge: A Human‐Triggered Jökulhlaup From a Subglacial Lake

Gaidos

Jøhannesson

Einarsson

et al. 2020

Geophysical Research Letters

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Glacial floods (jökulhlaups) are a phenomenon of some temperate ice masses; they are a significant natural hazard, but their complex hydrology is incompletely understood. We document a jökulhlaup from a subglacial lake in Iceland that was inadvertently triggered by a borehole drilled through the overlying ice. We propose that this borehole allowed an englacial water body to drain into the lake, inducing a transient rise in pressure that overwhelmed the lake's subglacial seal 5 days later. Runaway melting of a subglacial conduit by 4 • C lake water then initiated a flood to the outlet glacier margin. This incident suggests that draining of englacial water bodies via hydrofracturing crevasses and flooding of moulins by precipitation events are potential natural triggers of jökulhlaups and explains a correlation between surface melting and jökulhlaups. This hydraulic trigger could have wider implications for relations between meteorological conditions, drainage, and dynamics of some glaciers. Plain Language Summary Some ice caps and mountain glaciers contain water bodies that drain episodically and catastrophically as subglacial floods, sometimes threatening human life and property. Our observations suggest that we unintentionally triggered such a flood from a subglacial lake in Iceland by boring through the overlying ice. Our conduit allowed water inside the glacier to drain into the lake, causing the pressure to rise and lifting the ice shelf enough to allow the lake to rapidly drain beneath the glacier toward its edge. This event revealed a mechanism by which natural drainage events can trigger such floods and why floods from this particular lake are more likely to occur in summer. Hydrographs (flow vs. time) provide insight into causative mechanisms and dynamics of glacial floods, classifying them as either "slow rising" (1-2 weeks to peak discharge) or "fast rising" (up to 1-2 days).

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“…Although subglacial lakes were first mapped in Antarctica 28,29 and Iceland 30 over 50 years ago, they have only been identified beneath the Greenland Ice Sheet in the past decade 31,32 . Recently, dynamically active Greenlandic lakes have been discovered, which, unlike their Antarctic counterparts, are primarily fed by seasonal inputs of surface meltwater [32][33][34][35][36] . Active subglacial lakes have wider importance because they provide a mechanism to force large volumes of water and sediment through the subglacial hydrological system when they drain.…”

Section: Mainmentioning

confidence: 99%

Surface outburst of a subglacial flood from the Greenland Ice Sheet

Bowling

Leeson

McMillan

et al. 2021

Preprint

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As Earth’s climate warms, surface melting of the Greenland Ice Sheet is projected to intensify, contributing to rising sea levels1–4. Observations5–7 and theory8–10 indicate that meltwater generated at the surface of an ice sheet can drain to its bed via crevasses and moulins, where it flows relatively unhindered to the coast. This understanding of the movement of water within, and beneath, ice sheets, underpins theoretical models which are used to make projections of ice sheet change11. In this study, we show the first evidence of a disruptive drainage pathway in Greenland, whereby a subglacial flood – triggered by a draining subglacial lake – breaks through the ice sheet surface. This unprecedented outburst of water causes fracturing of the ice sheet, and the formation of 25-metre-high ice blocks. These observations reveal a complex, bidirectional coupling between the surface and basal hydrological systems of an ice sheet, which was previously unknown in Greenland. Analysis of over 30 years of satellite imagery confirms that the subglacial lake has drained at least once previously. However, on that occasion the floodwater failed to breach the ice surface. The two contrasting drainage regimes, coupled with the increased rates of ice melting and thinning that have occurred over the past three decades years, suggest that Arctic climate warming may have facilitated a new, disruptive mode of hydrological drainage on the ice sheet. As such, our observations reveal an emerging and poorly understood phenomenon, which is not currently captured in physical ice sheet models.

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Brief communication: Subglacial lake drainage beneath Isunguata Sermia, West Greenland: geomorphic and ice dynamic effects

Cited by 21 publications

References 20 publications

Supraglacial lake drainage at a fast-flowing Greenlandic outlet glacier

Supraglacial lake drainage at a fast-flowing Greenlandic outlet glacier

Après Nous, le Déluge: A Human‐Triggered Jökulhlaup From a Subglacial Lake

Surface outburst of a subglacial flood from the Greenland Ice Sheet

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