Amundsen Sea

The Amundsen Sea, an arm of the Southern Ocean off Marie Byrd Land in western Antarctica, lies between Cape Flying Fish (the northwestern tip of Thurston Island) to the east and Cape Dart on Siple Island to the west. Cape Flying Fish marks the boundary between the Amundsen Sea and the Bellingshausen Sea. West of Cape Dart there is no named marginal sea of the Southern Ocean between the Amundsen and Ross Seas. The Norwegian expedition of 1928–1929 under Captain Nils Larsen named the body of water for the Norwegian polar explorer Roald Amundsen 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 (1.9 mi) in thickness; roughly the size of the state of Texas, this 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.

AmundsenSea
The Amundsen Sea area of Antarctica
Antarctic Sea Ice - Amundsen Sea
Antarctic iceberg, Amundsen Sea

Amundsen Sea Embayment

Amundsen Sea Icebergs
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 (1.9 mi) 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 destabilise 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 riven 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 north 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]

Antarctic-seas-en
Amundsen Sea as part of the Southern Ocean

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) is a bay about 40 miles (64 km) long and 30 miles (48 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) 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 23 October 2011.
  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 978-0-00-200751-1.
  4. ^ Strom, Robert (2007). "The Melting Earth". Hot House: Global Climate Change and the Human Condition. Coprenicus Books. p. 302.
  5. ^ Black, Richard (20 January 2008). "Ancient Antarctic eruption noted". BBC News. London: BBC. Retrieved 22 October 2011.
  6. ^ Corr, H. F. J.; Vaughan, D. G. (2008). "A recent volcanic eruption beneath the West Antarctic ice sheet". Nature Geoscience. 1 (2): 122–125. Bibcode:2008NatGe...1..122C. doi:10.1038/ngeo106.
  7. ^ Mosher, Dave (20 January 2008). "Buried Volcano Discovered in Antarctica". Imaginova Corp. LiveScience.com. Retrieved 11 April 2009.
  8. ^ Payne, A. J.; Vieli, A.; Shepherd, A. P.; Wingham, D. J.; Rignot, E. (2004). "Recent dramatic thinning of largest West Antarctic ice stream triggered by oceans". Geophysical Research Letters. 31 (23): L23401. Bibcode:2004GeoRL..3123401P. CiteSeerX 10.1.1.1001.6901. doi:10.1029/2004GL021284.
  9. ^ Shepherd, A. P.; Wingham, D. J.; Rignot, E. (2004). "Warm ocean is eroding West Antarctic Ice Sheet". Geophysical Research Letters. 31 (23): L23402. Bibcode:2004GeoRL..3123402S. doi:10.1029/2004GL021106.
  10. ^ 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.
  11. ^ Barley, Shanta (13 January 2010). "Major Antarctic glacier is 'past its tipping point'". Reed Business Information Ltd. New Scientist. Archived from the original on 16 January 2010. 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 (2118): 1597. Bibcode:2010RSPSA.466.1597K. doi:10.1098/rspa.2009.0434.
  13. ^ "Pine Island Bay". Geographic Names Information System. United States Geological Survey. Retrieved 23 October 2011.
  14. ^ "Russell Bay". Geographic Names Information System. United States Geological Survey. Retrieved 23 October 2011.
  • Lubin, Dan; Massom, Robert (2006). Polar Remote Sensing. New York: Springer.
  • Schnellnhuber, Hans Joachim, ed. (2006). Avoiding Dangerous Climate Change. Cambridge: Cambridge University Press.

External links

Coordinates: 73°S 112°W / 73°S 112°W

Beakley Glacier

Beakley Glacier (73°51′S 119°50′W) is a glacier on the west side of the Duncan Peninsula on Carney Island, flowing north into the Amundsen Sea. It was delineated by the United States Geological Survey from aerial photos taken by U.S. Navy Operation Highjump in January 1947, and named by the Advisory Committee on Antarctic Names for Vice Admiral W.M. Beakley, U.S. Navy, Deputy Chief of Naval Operations for Ship Operations and Readiness during the IGY period, 1957–58.

Bellingshausen Sea

The Bellingshausen Sea is an area along the west side of the Antarctic Peninsula between 57°18'W and 102°20'W, west of Alexander Island, east of Cape Flying Fish on Thurston Island, and south of Peter I Island (there the southern Vostokkysten). In the south are, from west to east, Eights Coast, Bryan Coast and English Coast (west part) of West Antarctica. To the west of Cape Flying Fish it joins the Amundsen Sea.

Bellingshausen Sea has an area of 487,000 km2 (188,000 sq mi) and reaches a maximum depth of 4.5 kilometers (2.8 mi). It contains the undersea plain Bellingshausen Plain.

It takes its name from Admiral Thaddeus Bellingshausen, who explored in the area in 1821.

In the late Pliocene Epoch, about 2.15 million years ago, the Eltanin asteroid (about 1-4 km in diameter) impacted at the edge of the Bellingshausen sea (at the South Pacific Ocean). This is the only known impact in a deep-ocean basin in the world.

Burke Island

Burke Island is an ice-covered island about 30 km (16 nmi) long and 11 km (6 nmi) wide, lying 69 km (37 nmi) southwest of Cape Waite, King Peninsula, in the Amundsen Sea. Burke Island was delineated from aerial photographs taken by U.S. Navy Squadron VX-6 in January 1960. Burke Island was named by the United States Advisory Committee on Antarctic Names (US-ACAN) for Admiral Arleigh A. Burke, U.S. Navy, Chief of Naval Operations during Operation Deep Freeze (1956–1961).

Canisteo Peninsula

Canisteo Peninsula (73°48′S 102°20′W) is an ice-covered peninsula, about 30 miles (50 km) long and 20 miles (30 km) wide, which projects between Ferrero Bay and Cranton Bay into the eastern extremity of the Amundsen Sea. It was delineated from air photos taken by U.S. Navy Operation Highjump in December 1946, and named by the Advisory Committee on Antarctic Names for the USS Canisteo, a tanker with the eastern task group of this expedition.

Cape Flying Fish

Cape Flying Fish (72°3′S 102°20′W, also known as Cape Dart) is an ice-covered cape which forms the western extremity of Thurston Island. It was discovered by Rear Admiral Richard E. Byrd and members of the US Antarctic Service in a flight from the Bear in February 1940. It was named by the Advisory Committee on Antarctic Names for the United States Exploring Expedition ship Flying Fish, commanded by Lieutenant William M. Walker, U.S. Navy, which reached a point within 125 miles of this cape; the ship's position on the morning of March 23, 1839 was 70°0′S 100°16′W.Cape Flying Fish separates the Amundsen Sea in the west from the Bellingshausen Sea in the east. It constitutes the eastern boundary of the Walgreen Coast, and the western boundary of the Eights Coast.

Cranton Bay

Cranton Bay is a bay about 20 nmi (37 km; 23 mi) long and wide, lying south of the Canisteo Peninsula at the eastern end of the Amundsen Sea. The southern limit of the bay is formed by the Backer Islands and an ice shelf which separates this bay from Pine Island Bay. It was mapped from air photos taken by U.S. Navy Operation Highjump, 1946–47, and named by the Advisory Committee on Antarctic Names for Lieutenant Elmer M. Cranton, U.S. Navy, medical officer and officer in charge at Byrd Station, 1967.

Early Islands

The Early Islands (73°40′S 101°40′W) are a group of small islands lying just west of the Cosgrove Ice Shelf in the southeast corner of Ferrero Bay, Amundsen Sea. They were mapped by the United States Geological Survey from ground surveys and U.S. Navy air photos, 1960–66, and were named by the Advisory Committee on Antarctic Names for Tommy Joe Early, a biologist with the Ellsworth Land Survey, 1968–69.

Eights Coast

Eights Coast is that portion of the coast of West Antarctica between Cape Waite and Pfrogner Point. To the west is the Walgreen Coast, and to the east is the Bryan Coast. It is part of Ellsworth Land and stretches between 103°24'W and 89°35'W. This coast is bordered by Thurston Island, Abbot Ice Shelf and some islands within the ice shelf, and for most of its length touches the Bellingshausen Sea (west of Thurston Island by the Amundsen Sea). Most of Eights Coast is not claimed by any nation. In the east, Eights Coast borders the sector claimed by Chile as part of its southernmost province. Peter I Island, 450 km north of the coast, is claimed by Norway as a dependency.

The coast was sighted by members of the US Antarctic Service by flights from the USS Bear during February 1940. It was mapped in detail by the United States Geological Survey from surveys and from U.S. Navy air photographs, 1960–66. Eights Coast was named by the Advisory Committee on Antarctic Names for James Eights of Albany, New York, a geologist on the ship Annawan during 1830, who performed geological investigations of the South Shetland Islands, and who cruised westward on the Annawan, in company with the ship Penguin, to 103°W. Eights, the earliest American scientist in the Antarctic, discovered the first known fossils in the Antarctic region, a tree section in the South Shetland Islands. As a result of these investigations Eights, during 1833, published in the Transactions of the Albany Institute (Vol. 2) what proved to be remarkably accurate observations and conclusions concerning the natural phenomena of the region.

Erickson Bluffs

The Erickson Bluffs (75°2′S 136°30′W) are a series of conspicuous rock bluffs extending from Gilbert Bluff to Mount Sinha, forming the southwest edge of the McDonald Heights, near the coast of Marie Byrd Land, Antarctica. A portion of the bluffs were photographed from aircraft of the United States Antarctic Service, 1939–41. They were mapped by the United States Geological Survey from surveys and U.S. Navy air photos, 1959–65, and were named by the Advisory Committee on Antarctic Names for Albert W. Erickson, leader of a biology party that made population studies of seals, whales, and birds in the pack ice of the Bellingshausen Sea and Amundsen Sea using USCGC Southwind and its two helicopters, 1971–72.

Hudson Mountains

The Hudson Mountains is a group of parasitic cones, forming nunataks just above the Antarctic ice sheet in west Ellsworth Land. These mountains lie just east of Cranton Bay and Pine Island Bay at the eastern extremity of Amundsen Sea, and are bounded on the north by Cosgrove Ice Shelf and on the south by Pine Island Glacier.

King Peninsula

King Peninsula (72°12′S 100°15′W) is an ice-covered peninsula, 100 nautical miles (200 km) long and 20 nautical miles (40 km) wide, lying south of Thurston Island and forming the south side of Peacock Sound, Antarctica. It projects from the continental ice sheet and trends west between the Abbot Ice Shelf and Cosgrove Ice Shelf to terminate at the Amundsen Sea. The feature was photographed from the air by U.S. Navy Operation Highjump, 1946–47, and was plotted from these photos as a long island, or possible peninsula. Photos taken by the U.S. Navy in 1966 show it is a peninsula but the US Board on Geographic Names published its list of names that same year and designated the area as an island.King Peninsula was named by the Advisory Committee on Antarctic Names for Fleet Admiral Ernest J. King, U.S. Navy, Chief of Naval Operations from 1942–45, who approved the preliminary work for Operation Highjump.

Lindsey Islands

Lindsey Islands (73°37′S 103°18′W) is a group of islands lying just off the northwest tip of Canisteo Peninsula in Amundsen Sea. Delineated from air photos taken by U.S. Navy Operation Highjump in December 1946. Named by Advisory Committee on Antarctic Names (US-ACAN) for Alton A. Lindsey, biologist with the Byrd Antarctic Expedition, 1933-35.

Melanella antarctica

Melanella antarctica is a species of sea snail, a marine gastropod mollusk in the family Eulimidae. The species is one of many species known to exist within the genus, Melanella. As the biological classification states, this species is notable for being mainly distributed in southern waters, these would include the Amundsen Sea, Bellingshausen Sea, Weddell Sea and the Ross Sea respectively.

Pine Island Glacier

Pine Island Glacier (PIG) is a large ice stream, and the fastest melting glacier in Antarctica, responsible for about 25% of Antarctica's ice loss. The glacier ice streams flow west-northwest along the south side of the Hudson Mountains into Pine Island Bay, Amundsen Sea, Antarctica. It was mapped by the United States Geological Survey (USGS) from surveys and United States Navy (USN) air photos, 1960–66, and named by the Advisory Committee on Antarctic Names (US-ACAN) in association with Pine Island Bay.The area drained by Pine Island Glacier comprises about 10% of the West Antarctic Ice Sheet. Satellite measurements have shown that the Pine Island Glacier Basin has a greater net contribution of ice to the sea than any other ice drainage basin in the world and this has increased due to recent acceleration of the ice stream.The ice stream is extremely remote, with the nearest continually occupied research station at Rothera, nearly 1,300 km (810 mi) away. The area is not claimed by any nations and the Antarctic Treaty prohibits any new claims while it is in force.

Smith Glacier

Smith Glacier is a low-gradient Antarctic glacier, over 160 km (100 mi) long, draining from Toney Mountain in an ENE direction to Amundsen Sea. A northern distributary, Kohler Glacier, drains to Dotson Ice Shelf but the main flow passes to the sea between Bear Peninsula and Mount Murphy, terminating at Crosson Ice Shelf.

Mapped by USGS from ground surveys and USN air photos, 1959–65. Named by US-ACAN after Philip M. Smith (Smith Bluffs), Deputy Director, Office of Polar Programs, National Science Foundation, who in the period 1956–71 participated in a large number of expeditions to Antarctica in field and supervisory capacities.

Thurston Island

Thurston Island is an ice-covered, glacially dissected island, 215 km (134 mi) long, 90 km (56 mi) wide and 15,700 km2 (6,062 sq mi) in area, lying a short way off the northwest end of Ellsworth Land, Antarctica. It is the third largest island of Antarctica, after Alexander Island and Berkner Island.

The island was discovered from the air by Rear Admiral Byrd on February 27, 1940, who named it for W. Harris Thurston, New York textile manufacturer, designer of the windproof "Byrd Cloth" and sponsor of Antarctic expeditions.Thurston Island is separated from the mainland by Peacock Sound, which is occupied by the western portion of Abbot Ice Shelf. It divides Bellingshausen Sea to the east from Amundsen Sea to the west.

Originally charted as a peninsula, the feature was not recognised an island until 1960.

Thwaites Glacier

Thwaites Glacier (75°30′S 106°45′W) is an unusually broad and fast Antarctic glacier flowing into Pine Island Bay, part of the Amundsen Sea, east of Mount Murphy, on the Walgreen Coast of Marie Byrd Land. Its surface speeds exceed 2 km/yr near its grounding line. Its fastest flowing grounded ice is centred between 50 and 100 km east of Mount Murphy. It was named by ACAN after Fredrik T. Thwaites, a glacial geologist, geomorphologist and professor emeritus at the University of Wisconsin–Madison. Thwaites Glacier is closely watched for its potential to raise sea levels.Along with Pine Island Glacier, Thwaites Glacier has been described as part of the "weak underbelly" of the West Antarctic Ice Sheet, due to its apparent vulnerability to significant retreat. This hypothesis is based on theoretical studies of the stability of marine ice sheets and observations of large changes on both of these glaciers. In recent years, the flow of both of these glaciers has accelerated, their surfaces have lowered, and the grounding lines have retreated.

Waite Islands

Waite Islands is a group of small islands in the Amundsen Sea, lying 11 kilometres (6 nmi) west of Cape Waite, the northwest extremity of King Peninsula. Mapped by United States Geological Survey (USGS) from surveys and U.S. Navy air photos, 1960-66. Named by Advisory Committee on Antarctic Names (US-ACAN) for their proximity to Cape Waite.

West Antarctic Ice Sheet

The Western Antarctic Ice Sheet (WAIS) is the segment of the continental ice sheet that covers West (or Lesser) Antarctica, the portion of Antarctica on the side of the Transantarctic Mountains which lies in the Western Hemisphere. The WAIS is classified as a marine-based ice sheet, meaning that its bed lies well below sea level and its edges flow into floating ice shelves. The WAIS is bounded by the Ross Ice Shelf, the Ronne Ice Shelf, and outlet glaciers that drain into the Amundsen Sea.

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Atlantic Ocean
Indian Ocean
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Endorheic basins

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