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211:. In such a flood, the lake water releases rushes down a valley. These events are sudden and catastrophic and thus provide little warning to people who live downstream, in the path of the water. In Himalayan regions, villages cluster around water sources, such as proglacial streams; these streams are the same pathways the glacial lake outburst floods travel down.
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Sedimentary particles often accumulate in supraglacial lakes; they are washed in by the meltwater or rainwater that supplies the lakes. The character of the sediment depends upon this water source, as well as the proximity of a sampled area to both the edge of the glacier and the edge of the lake.
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is increasing the abundance of supraglacial lakes on the
Greenland Ice Sheet. However, recent research has shown that supraglacial lakes have been forming in new areas. In fact, satellite photos show that since the 1970s, when satellite measurements began, supraglacial lakes have been forming at
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data also reveal that high-elevation lakes rarely form new moulins there. Thus, the role of supraglacial lakes in the basal hydrology of the ice sheet is unlikely to change in the near future: they will continue to bring water to the bed by forming moulins within a few tens of kilometers of the
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Climate change is having a more severe effect on supraglacial lakes on mountain glaciers. In the
Himalaya, many glaciers are covered by a thick layer of rocks, dirt, and other debris; this debris layer insulates the ice from the warmth of the sun, allowing more ice to stay solid when air
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temperatures rise above the melting point. Water collecting on the ice surface has the opposite effect, due to its high albedo as described in a previous section. Thus, more supraglacial lakes lead to a vicious cycle of more melting and more supraglacial lakes. A good example is the
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The drainage of supraglacial lakes on mountain glaciers can disrupt the internal plumbing structure of the glacier. Natural events such as landslides or the slow melting of a frozen
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Lakes may be created by surface melting during summer months, or over the period of years by rainfall, such as monsoons. They may dissipate by overflowing their banks, or creating a
77:. When these crevasses form, it can take a mere 2–18 hours to empty a lake, supplying warm water to the base of the glacier - lubricating the bed and causing the glacier to
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Sediments are dominated by coarser (coarse sand/gravel) fragments, and the accumulation rate can be immense: up to 1 metre per year near the shores of larger lakes.
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steadily higher elevations on the ice sheet as warmer air temperatures have caused melting to occur at steadily higher elevations. However, satellite imagery and
267:
Climate Change 2007: The
Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change
43:, they may reach kilometers in diameter and be several meters deep. They may last for months or even decades at a time, but can empty in the course of hours.
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The amount of debris atop the glacier also has a large effect. Naturally, long lived lakes have a different sedimentary record to shorter lived pools.
115:; some are deep enough to be density stratified. Most have been growing since the 1950s; the glaciers have been retreating constantly since then.
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Lakes of a diameter greater than ~300 m are capable of driving a fluid-filled crevasse to the glacier/bed interface, through the process of
258:
Lemke, P.; Ren, J.; Alley, R.B.; Allison, I.; Carrasco, J.; Flato, G.; Fujii, Y.; Kaser, G.; Mote, P.; Thomas, R.H.; Zhang, T. (2007).
409:“Response of Debris-Covered Glaciers in the Mount Everest Region to Recent Warming, and Implications for Outburst Flood Hazards.”
230:"Constraints on melt-water flux through the West Greenland ice-sheet: modeling of hydro-fracture drainage of supraglacial lakes"
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Such lakes are also prominent in
Greenland, where they have recently been understood to contribute somewhat to ice movement.
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Benn, D I, T Bolch, K Hands, J Gulley, A Luckman, L I Nicholson, D Quincey, S Thompson, R Toumi, and S Wiseman. 2012.
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produce vast and long lived lakes, many kilometres in diameter and scores of metres deep. These may be bounded by
285:
Chikita, K.; Jha, J.; Yamada, T. (2001). "Sedimentary effects on the expansion of a
Himalayan supraglacial lake".
265:. In Solomon, S.; Qin, D.; Manning, M.; Chen, Z.; Marquis, M.; Averyt, K.B.; Tignor, M.; Miller, H.L. (eds.).
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than ice, the water absorbs more of the sun's energy, causing warming and (potentially) further melting.
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396:“Limits to Future Expansion of Surface‐Melt‐Enhanced Ice Flow Into the Interior of Western Greenland.”
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Earth-Science
Reviews 114 (1-2). Elsevier B.V.: 156–74. doi:10.1016/j.earscirev.2012.03.008.
8:
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Howat, I M, S de la Peña, J H van
Angelen, J T M Lenaerts, and M R van den Broeke. 2013.
89:, may penetrate to the underlying ocean and contribute to the breakup of the ice shelf.
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200:, the longest glacier in the Himalayas, which counts numerous supraglacial lakes.
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236:. Vol. 88. pp. Fall Meet. Suppl., Abstract C41B–0474. Archived from
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Supraglacial lakes also have a warming effect on the glaciers; having a lower
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323:"Sediment record of short-lived ice-contact lakes, Burroughs Glacier, Alaska"
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Upon melting of the glacier, deposits may be preserved as superglacial till (
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A proliferation of supraglacial lakes preceded the collapse of the
Antarctic
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81:. The rate of emptying such a lake is equivalent to the rate of flow of the
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73:. A surface-to-bed connection made in this way is referred to as a
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36:
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Krawczynski, M.J.; Behn, M.D.; Das, S.B.; Joughin, I. (2007).
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383:“Expansion of Meltwater Lakes on the Greenland Ice Sheet.”
398:
Geophysical
Research Letters. doi:10.1002/2015GL063192.
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can incite drainage of a supraglacial lake, creating a
260:"Observations: Changes in Snow, Ice and Frozen Ground"
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Supraglacial lakes can occur in all glaciated areas.
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394:Poinar, K, I Joughin, S B Das, and M D Behn. 2015.
137:Accumulated supraglacial debris, Ngozumpa glacier.
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385:The Cryosphere 7 (1). doi:10.5194/tc-7-201-2013.
122:ice shelf in 2001, and may have been connected.
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187:A supraglacial lake on the surface of the
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366:Details of supraglacial lake research
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85:. Such crevasses, when forming on
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339:10.1111/j.1502-3885.1998.tb00866.x
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372:, a specialist. Contains images.
107:The retreating glaciers of the
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299:10.1016/S0921-8181(00)00062-X
269:. Cambridge University Press.
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165:It was once unclear whether
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39:. Although these pools are
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287:Global and Planetary Change
209:glacial lake outburst flood
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156:Effect of global warming
321:Syverson, K.M. (1998).
152:supraglacial moraine).
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215:References
63:See also:
370:Sarah Das
347:129000793
129:Sediments
41:ephemeral
422:Category
179:Himalaya
120:Larsen B
113:moraines
109:Himalaya
47:Lifetime
27:in 1995.
205:moraine
175:coast.
100:Context
37:glacier
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327:Boreas
94:albedo
75:moulin
53:moulin
368:from
343:S2CID
263:(PDF)
150:alias
79:surge
335:doi
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