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 (1883 - 1961), a glacial geologist, geomorphologist and professor emeritus at the University of Wisconsin–Madison. Reuben Gold Thwaites was his father.
Thwaites Glacier is closely watched for its potential to raise sea levels. Along with Pine Island Glacier, it 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.
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. However, the glacier has been considered to be the biggest threat on relevant time scales, for rising seas, current studies aim to better quantify retreat and possible impacts. Since the 1980s, the glacier has had a net loss of over 600 billion tons of ice.
Water drainage beneath the glacier
Swamp-like canal areas and streams underlie the glacier. The upstream swamp canals 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.
A 2014 University of Washington study, using satellite measurements and computer models, predicted that the Thwaites Glacier will gradually melt, leading to an irreversible collapse over the next 200 to 1000 years.
Features and observation
Thwaites Glacier Tongue
The Thwaites Glacier Tongue, or Thwaites Ice Tongue (75°0′S 106°50′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) 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. It was first noted in the 1930s, but finally detached from the ice tongue and broke up in the late 1980s.
In January 2019, NASA discovered an underwater cavity underneath the glacier, with an area two-thirds the size of Manhattan. The cavity formed mostly in the previous three years and is nearly a thousand feet tall, likely speeding up the glacier's decay. Thwaites currently contributes roughly 4% to global sea level rise.
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This article incorporates public domain material from the United States Geological Survey document "Thwaites Glacier" (content from the Geographic Names Information System).