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Amundsen Sea

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The Amundsen Sea area of Antarctica
Antarctic iceberg, Amundsen Sea

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The Amundsen Sea is an arm of the Southern Ocean off Marie Byrd Land in western Antarctica. It is bounded by Thurston Island to the east and Cape Dart to the west. Named for the Norwegian polar explorer Roald Amundsen by the Norwegian expedition of 1928-29, under Captain Nils Larsen, while exploring this area in February, 1929.[1]

The sea is mostly ice-covered, and the Thwaites Ice Tongue protrudes into it. The ice sheet which drains into the Amundsen Sea averages about 3 km (2 miles) in thickness; is roughly the size of the state of Texas and the area is known as the Amundsen Sea Embayment (ASE); it forms one of the three major ice drainage basins of the West Antarctic Ice Sheet.

Amundsen Sea Embayment

Large B-22 iceberg breaking off from Thwaites Glacier and remnants of the B-21 iceberg from Pine Island Glacier in Pine Island Bay to the right of the image

The ice sheet which drains into the Amundsen Sea averages about 3 km (2 miles) in thickness; is roughly the size of the state of Texas and the area is known as the Amundsen Sea Embayment (ASE); it forms one of the three major ice drainage basins of the West Antarctic Ice Sheet, the others being the Ross Sea Embayment and the Weddell Sea Embayment. In March 2007, scientists studying the ASE through satellite and airborne surveys announced a significant thinning of the ASE, due to shifts in wind patterns that allow warmer waters to flow beneath the ice sheet.

Some scientists have proposed that this region may be a "weak underbelly" of the West Antarctic Ice Sheet. The Pine Island and Thwaites Glaciers, which both flow into the Amundsen Sea, are two of Antarctica's largest five. Scientists have found that the flow of these glaciers has increased in recent years, if they were to melt completely global sea levels would rise by about 0.9-1.9 m (1-2 yards). Scientist have suggested that the loss of these glaciers would destabilize the entire West Antarctic ice sheet and possibly sections of the East Antarctic Ice Sheet.[2]

A study in October 2004 suggested that because the ice in the Amundsen Sea had been melting rapidly and became riveted with cracks, the offshore ice shelf was set to collapse "within five years". The study projected a sea level rise of 1.3 m (4.3 ft) from the West Antarctic Ice Sheet if all the sea ice in the Amundsen Sea melted.[3]

Measurements made by the British Antarctic Survey in 2005 showed that the ice discharge rate into the Amundsen Sea embayment was about 250 km3 per year. Assuming a steady rate of discharge, this alone is sufficient to raise global sea levels by 0.2 mm per year.[4]

A subglacial volcano has also been detected in the area, just west of the Pine Island Glacier near the Hudson Mountains. It last erupted approximately 2,200 years ago, indicated by widespread ash deposits within the ice, in what was the largest known eruption in Antarctica within the past 10 millennia.[5][6] Volcanic activity in the region may be contributing to the observed increase of glacial flow,[7] although currently the most popular theory amongst the scientists studying this area is that the flow has increased due to warming ocean water.[8][9] This water has warmed due to an upwelling of deep ocean water which is due to variations in pressure systems, which could have been affected by global warming.[10]

In January 2010, a modelling study suggested that the "tipping point" for Pine Island Glacier may have been passed in 1996, with a retreat of 200 km possible by 2100, producing a corresponding 24 cm (0.79 ft) of sea level rise, although it was suggested that these estimates for timespan were conservative.[11] However, the modelling study also states that "Given the complex, three-dimensional nature of the real Pine Island glacier ... it should be clear that the [...] model is a very crude representation of reality."[12]

Pine Island Bay

Pine Island Bay (74°50′S 102°40′W / 74.833°S 102.667°W / -74.833; -102.667) is a bay about 40 miles (65 km) long and 30 miles (50 km) wide, into which flows the ice of the Pine Island Glacier at the southeast extremity of the Amundsen Sea. It was delineated from aerial photographs taken by USN Operation Highjump in December 1946, and named by the Advisory Committee on Antarctic Names (US-ACAN) for the USS Pine Island, seaplane tender and flagship of the eastern task group of USN Operation Highjump which explored this area.[13]

Russell Bay

Russell Bay (73°27′S 123°54′W / 73.450°S 123.900°W / -73.450; -123.900) is a rather open bay in southwestern Amundsen Sea, extending along the north sides of Siple Island, Getz Ice Shelf and Carney Island, from Pranke Island to Cape Gates. It was mapped by United States Geological Survey (USGS) from surveys and U.S. Navy air photos, 1959-66, and named by the Advisory Committee on Antarctic Names (US-ACAN) for Admiral James S. Russell, USN, Vice Chief of Naval Operations during the post 1957-58 IGY period.[14]

References

  1. ^ "Amundsen Sea". Geographic Names Information System. United States Geological Survey. Retrieved 2009-05-03.
  2. ^ Pearce, Fred (2007). With Speed and Violence: Why scientists fear tipping points in climate change. Beacon Press Books. ISBN 978-0-8070-8576-9.
  3. ^ Flannery, Tim F. (2006). The Weather Makers: How man is changing the climate and what it means for life on Earth. HarperCollins. p. 356. ISBN 0002007517.
  4. ^ Strom, Robert (2007). "The Melting Earth". Hot House: Global Climate Change and the Human Condition. Coprenicus Books. p. 302.
  5. ^ BBC NEWS, Ancient Antarctic eruption noted
  6. ^ Corr H.F.J., Vaughan D.G. (2008). "A recent volcanic eruption beneath the West Antarctic ice sheet". Nature Geoscience. 1: 122–125. doi:10.1038/ngeo106.
  7. ^ Mosher, Dave (January 20, 2008). "Buried Volcano Discovered in Antarctica". Imaginova Corp. LiveScience.com. Retrieved 2009-04-11.
  8. ^ Payne A.J., Vieli A., Shepherd A.P., Wingham D.J., Rignot E. (2004). "Recent Warm Ocean is erroding West Antarctic Ice Sheet". Geophys. Res. Lett. 31: L23402. doi:10.1029/2004GL021284.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  9. ^ Shepherd A.P., Wingham D.J., Rignot E. (2004). "Recent dramatic thinning of largest West Antarctic ice stream triggered by oceans". Geophys. Res. Lett. 31: L23401. doi:10.1029/2004GL021106.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  10. ^ Thoma M., Jenkins A., Holland D., Jacobs S. (2008). "Modelling Circumpolar Deep Water intrusions on the Amundsen Sea continental shelf, Antarctica". Geophys. Res. Lett. 35: L18602. doi:10.1029/2008GL034939.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  11. ^ Barley, Shanta (January 13, 2010). "Major Antarctic glacier is 'past its tipping point'". Reed Business Information Ltd. NewScientist. Retrieved 17 January 2010.
  12. ^ Katz R.F., Worster M.G. (2010). "Stability of ice sheet grounding lines". Proceedings of the Royal Society A. 466: 1597. doi:10.1098/rspa.2009.0434.
  13. ^ "Pine Island Bay". Geographic Names Information System. United States Geological Survey. Retrieved 2009-05-03.
  14. ^ "Russell Bay". Geographic Names Information System. United States Geological Survey. Retrieved 2009-05-06.
  • Lubin, Dan, and Robert Massom. Polar Remote Sensing. New York, Springer, 2006.
  • Schnellnhuber, Hans Joachim, et al., eds. Avoiding Dangerous Climate Change. Cambridge, Cambridge University Press, 2006.
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