Marine ice sheet instability: Difference between revisions
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==Example== |
==Example== |
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{{See also|West Antarctic Ice Sheet#Potential collapse}} |
{{See also|West Antarctic Ice Sheet#Potential collapse}} |
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The [[Thwaites glacier|Thwaites]] and [[Pine Island glacier|Pine Island]] glaciers have been identified to be potentially prone to these processes, since both glaciers [[bedrock]] gets deeper farther inland, exposing them to more warm water intrusion at the grounding line, and with the continued melt, retreat, eventually raising global sea levels.<ref>{{cite web|url=https://www.theatlantic.com/science/archive/2018/06/after-decades-of-ice-loss-antarctica-is-now-hemorrhaging-mass/562748/|work=The Atlantic|year=2018|title=After Decades of Losing Ice, Antarctica Is Now Hemorrhaging It}}</ref><ref>{{cite web|url=http://www.antarcticglaciers.org/glaciers-and-climate/ice-ocean-interactions/marine-ice-sheets/|work=AntarcticGlaciers.org|year=2014|title=Marine ice sheet instability}}</ref> |
The [[Thwaites glacier|Thwaites]] and [[Pine Island glacier|Pine Island]] glaciers have been identified to be potentially prone to these processes, since both glaciers' [[bedrock]] gets deeper farther inland, exposing them to more warm water intrusion at the grounding line, and with the continued melt, retreat, eventually raising global sea levels.<ref>{{cite web|url=https://www.theatlantic.com/science/archive/2018/06/after-decades-of-ice-loss-antarctica-is-now-hemorrhaging-mass/562748/|work=The Atlantic|year=2018|title=After Decades of Losing Ice, Antarctica Is Now Hemorrhaging It}}</ref><ref>{{cite web|url=http://www.antarcticglaciers.org/glaciers-and-climate/ice-ocean-interactions/marine-ice-sheets/|work=AntarcticGlaciers.org|year=2014|title=Marine ice sheet instability}}</ref> |
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==See also== |
==See also== |
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Marine Ice Sheet Instability (MISI) is a regional situation, to describe ice sheets which are grounded below sea level, and where the Ocean floor gets more deep farther upstream. This circumstance can facilitate processes resulting in the acceleration of ice sheet retreat.[1][better source needed][2]
General
If water temperatures at the base of ice shelves are warm enough, melt increases (basal melt), and if the local topography where an ice sheet is located also deepens further inland (retrograde slope), the thinning of ice shelves which stabilize the ice sheet, exert less of an buttressing effect (back stress). This can result in a runaway retreat of an ice sheet, because the depth of the grounding line, the part where a marine terminating glacier is submerged by ocean waters, and meets the seafloor, is strongly linked to ice discharge rates.[1]
A process known as Marine Ice Cliff Instability (MICI) can further speed up ice sheet retreat, where surface melt creates crevasses on the floating ice shelf extensions, fracturing them, accelerating ice discharge, once gone, subsequently further destabilizing the now exposed ocean-facing ice sheet or glacier (Ice cliffs), if the cliffs are ∼90 m above sea level.[3]
The breakup of ice at the ice sheet periphery, at the ice cliffs and ice shelf, is called ice calving, and creates new ice bergs.
Ocean warming
According to a 2016 published study, cold meltwater provides cooling of the ocean's surface layer, acting like a lid, and also affecting deeper waters by increasing subsurface ocean warming and thus facilitating ice melt.
Our “pure freshwater” experiments show that the low-density lid causes deep-ocean warming, especially at depths of ice shelf grounding lines that provide most of the restraining force limiting ice sheet discharge.[4]
Another theory discussed in 2007 for increasing warm bottom water is that that changes in air circulation patterns have led to increased upwelling of warm, deep ocean water along the coast of Antarctica and that this warm water has increased melting of floating ice shelves.[5] An ocean model has shown how changes in winds can help channel the water along deep troughs on the sea floor, toward the ice shelves of outlet glaciers.[6]
Example
The Thwaites and Pine Island glaciers have been identified to be potentially prone to these processes, since both glaciers' bedrock gets deeper farther inland, exposing them to more warm water intrusion at the grounding line, and with the continued melt, retreat, eventually raising global sea levels.[7][8]
See also
References
- ^ a b "Potential Antarctic Ice Sheet retreat driven by hydrofracturing and ice cliff failure". Nature. 2015. doi:10.1016/j.epsl.2014.12.035.
{{cite journal}}: Unknown parameter|authors=ignored (help) - ^ David Docquier (2016). "Marine Ice Sheet Instability "For Dummies"". EGU.
- ^ Pattyn, Frank (2018). "The paradigm shift in Antarctic ice sheet modelling". Nature Communications. 9 (1). doi:10.1038/s41467-018-05003-z. ISSN 2041-1723.
- ^ J. Hansen; M. Sato; P. Hearty; R. Ruedy; M. Kelley; V. Masson-Delmotte; G. Russell; G. Tselioudis; J. Cao; E. Rignot; I. Velicogna; E. Kandiano; K. von Schuckmann; P. Kharecha; A. N. Legrande; M. Bauer; K.-W. Lo (2016). "Ice melt, sea level rise and superstorms: evidence from paleoclimate data, climate modeling, and modern observations that 2 °C global warming could be dangerous". Atmospheric Chemistry and Physics (ACP). 16: 3761–3812. doi:10.5194/acp-16-3761-2016.
{{cite journal}}: Cite has empty unknown parameter:|1=(help)CS1 maint: unflagged free DOI (link) - ^ "Statement: Thinning of West Antarctic Ice Sheet Demands Improved Monitoring to Reduce Uncertainty over Potential Sea-Level Rise". Jsg.utexas.edu. Retrieved 26 October 2017.
- ^ Thoma, M.; Jenkins, A.; Holland, D.; Jacobs, S. (2008). "Modelling Circumpolar Deep Water intrusions on the Amundsen Sea continental shelf, Antarctica". Geophysical Research Letters. 35 (18): L18602. Bibcode:2008GeoRL..3518602T. doi:10.1029/2008GL034939.
- ^ "After Decades of Losing Ice, Antarctica Is Now Hemorrhaging It". The Atlantic. 2018.
- ^ "Marine ice sheet instability". AntarcticGlaciers.org. 2014.