Thwaites Glacier

The Thwaites Glacier

Thwaites Glacier (75°30′S 106°45′W / 75.500°S 106.750°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.^[1] Its surface speeds exceed 2 km/yr near its grounding line, and its fastest flowing grounded ice is centred between 50 and 100 km east of Mount Murphy. It was named by ACAN^[2] after Fredrik T. Thwaites, a glacial geologist, geomorphologist and professor emeritus at the University of Wisconsin–Madison.^[3] Thwaites Glacier drains into West Antarctica’s Amundsen Sea and 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 both theoretical studies of the stability of marine ice sheets and recent observations of large changes on both of these glaciers. In recent years, the flow of both of these glaciers have accelerated, their surfaces lowered, and the grounding lines retreated.

In 2011, using geophysical data collected from flights over Thwaites Glacier (data collected under NASA's Ice Bridge campaign), a study by scientists at Columbia University’s Lamont-Doherty Earth Observatory showed a rock feature, a ridge 700 meters tall that helps anchor the glacier and helped slow the glacier's slide into the sea. The study also confirmed the importance of seafloor topography in predicting how the glacier will behave in the near future.^[4]

Thwaites Glacier Tongue

The B-22 iceberg broken off from the Thwaites Glacier Tongue

The Thwaites Glacier Tongue, or Thwaites Ice Tongue (75°0′S 106°50′W / 75.000°S 106.833°W), is about 50 km wide and has progressively shortened due to ice calving, based on the observational record. It was initially delineated from aerial photographs collected during Operation Highjump in January 1947.

On 15 March 2002, the National Ice Center reported that an iceberg named B-22 broke off from the ice tongue. This iceberg was about 85 km long by 65 km wide, with a total area of some 5,490 km². As of 2003, B-22 had broken into five pieces, with B-22A still in the vicinity of the tongue, while the other smaller pieces had drifted farther west.

Thwaites Iceberg Tongue

The Thwaites Iceberg Tongue (74°0′S 108°30′W / 74.000°S 108.500°W) was a large iceberg tongue which was aground in the Amundsen Sea, about 32 km northeast of Bear Peninsula. The feature was about 112 km long and 32 km wide, and in January 1966 its southern extent was only 5 km north of Thwaites Glacier Tongue. It consisted of icebergs which had broken off from the Thwaites Ice Tongue and ran aground, and should not be confused with the latter, which is still attached to the grounded ice. It was delineated by the USGS from aerial photographs collected during Operation Highjump and Operation Deepfreeze.^[5] It was first noted in the 1930s, but finally detached from the ice tongue and broke up in the late 1980s.^[6][7]

Water drainage beneath the glacier

Swamp-like areas and streams underlie the glacier. The upstream swamps feed streams with dry areas between the streams which retard flow of the glacier. Due to this friction the glacier is considered stable in the short term.^[8]

Predicted collapse

A University of Washington study, using satellite measurements and computer models, determined that the Thwaites Glacier will gradually melt, leading to an irreversible collapse over the next 200 to 1000 years.^[9]

See also

• Retreat of glaciers since 1850

References

1. "Thwaites Glacier: Antarctica, name, geographic coordinates, description, map". Geographic.org. Retrieved 2014-05-13.
2. "Thwaites Glacier Tongue". Geographic Names Information System. United States Geological Survey. Retrieved 23 October 2011.
3. "Thwaites Glacier". Geographic Names Information System. United States Geological Survey. Retrieved 23 October 2011.
4. http://www.earth.columbia.edu/articles/view/2904
5. "Thwaites Iceberg Tongue". Geographic Names Information System. United States Geological Survey. Retrieved 23 October 2011.
6. Reynolds, Larry (4 March 2000). "Where a cold tongue isn't". Teachers Experiencing Antarctica. Retrieved 16 June 2009.
7. Lucchitta, B.K.; Smith, C.E.; Bowel, J.; Mullins, K.F. (1994). "Velocities and mass balance of Pine Island Glacier, West Antarctica, derived from ERS-1 SAR". Pub. SP-361, 2nd ERS-1 Symposium, Space at the Service of Our Environment, Hamburg, Germany, 11–14, Oct. 1993 Proceedings. pp. 147–151.
8. "Scientists Image Vast Subglacial Water System Underpinning West Antarctica’s Thwaites Glacier". University of Texas. July 9, 2013. Retrieved July 9, 2013.
9. "Irreversible collapse of Antarctic glaciers has begun, studies say". Los Angeles Times. May 12, 2014. Retrieved May 13, 2014.

•  This article incorporates public domain material from the United States Geological Survey document "Thwaites Glacier" (content from the Geographic Names Information System).