Thwaites Glacier | |
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Doomsday Glacier | |
![]() Thwaites Glacier | |
Type | Tidewater valley |
Coordinates | Coordinates: 75°30′S106°45′W / 75.500°S 106.750°W |
Width | 120 kilometers [1] |
Lowest elevation | Below sea level |
Terminus | Pine Island Bay, part of the Amundsen Sea |
Status | Receding |
Thwaites Glacier, nicknamed the Doomsday Glacier, [2] is an unusually broad and vast Antarctic glacier flowing into Pine Island Bay, part of the Amundsen Sea, east of Mount Murphy, on the Walgreen Coast of Marie Byrd Land. [3] Its surface speeds exceed 2 kilometres (1.2 miles) per year near its grounding line. Its fastest-flowing grounded ice is centered between 50 and 100 kilometres (31 and 62 mi) east of Mount Murphy. In 1967, the Advisory Committee on Antarctic Names named the glacier after Fredrik T. Thwaites (1883–1961), a glacial geologist, geomorphologist and professor emeritus at the University of Wisconsin–Madison. [4] [5]
Thwaites Glacier is closely monitored for its potential to raise sea levels. [6] Along with the Pine Island Glacier, it has been described as part of the "weak underbelly" of the West Antarctic Ice Sheet, because of its apparent vulnerability to significant retreat. This hypothesis is based on both theoretical studies of the stability of marine ice sheets and observations of large changes on these two glaciers. In recent years, the flow of both of these glaciers has accelerated, their surfaces have lowered, and their grounding lines have retreated.
The Thwaites Ice Shelf, a floating ice shelf which braces and restrains the eastern portion of Thwaites Glacier, is likely to collapse within a decade from 2021. [7] [8] [9] While the glacier itself would still take approximately several centuries to collapse even after the loss of its ice shelf, its outflow and contribution to sea-level rise would accelerate substantially; while it currently amounts to 4% of global sea level rise, it would become equivalent to 5% in the short term, and likely accelerate further in the longer term. [10] For this reason, Thwaites Glacier and its ice shelf have been proposed as sites for climate engineering interventions to stabilize and preserve its ice. [11]
In 2001, a study of Thwaites Glacier using satellite radar interferometry data from the Earth Remote Sensing Satellite 1 and 2 revealed that the grounding line of Thwaites Glacier was retreating at 1 kilometre (0.62 mi) per year and that the glacier was significantly out of mass balance, hence confirming presumptions of collapse by Terence Hughes, University of Maine, in 1973. In 2002, a team of scientists from Chile and NASA on board a P-3 Orion from the Chilean Navy collected the first radar sounding and laser altimetry survey of the glacier to reveal extensive thinning and acceleration in thinning. This discovery prompted an extensive airborne campaign in 2004 by the University of Texas at Austin, to be followed by subsequent airborne campaigns under NASA's IceBridge Campaign in 2009–2018.
In 2011, using geophysical data collected from flights over Thwaites Glacier (data collected under NASA's IceBridge campaign), a study by scientists at Columbia University's Lamont–Doherty Earth Observatory showed a rock feature, a ridge 700 m (2,300 ft) 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. [12] 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. [13]
Since the 1980s, the glacier had a net loss of over 600 billion tons of ice up to 2017. [14] In 2017, scientists discovered previously unknown volcanoes nearby. [15]
In 2020, scientists discovered warm water underneath the glacier for the first time. [16] [17] The place where the glacier was in contact with the sea had been recorded as 2 degree Celsius above the freezing temperature. [18] The discovery was a part of the International Thwaites Glacier Collaboration, a partnership primarily between US and UK academic institutions. This study has raised alarm regarding the glacier collapse, which can lead to nearly 3 ft (0.9 m) rise in the sea level. [19] Scientists noted that subglacial lakes upstream of Thwaites may have caused a minor speedup of the glacier near the grounding line in early 2013. [20]
Extensive calving at the marine terminus of Thwaites Glacier is monitored by remote sensing and seismological observations, with the largest events being seismically detectable at ranges up to 1,600 km (990 mi). [21]
A 2022 study by Nature Geoscience described the "rapid retreat" of the Thwaites Glacier, inferring its past movement in the pre-satellite era by analyzing "ribs" formed on the ocean floor by tides and the ice. The study found that at some point in the last two centuries, the glacier moved 2.1 km (1.3 mi) per year, twice the rate it did between 2011–2019, making such a rate of retreat a possible threat, if the glacier recedes and is dislodged beyond a sea bed that is currently keeping it somewhat stable. [22] [23]
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. [24]
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 1,000 years. [25] [26] [27] [28] [29] [30]
A 2021 study suggested that the Thwaites Ice Shelf, which currently restrains the eastern portion of the Thwaites Glacier, could start to collapse within five years, leading to the contribution to sea level rise from the eastern portion increasing and eventually becoming equivalent to that of the other, undefended portions of the glacier. [8] Scientists do not assert that the entire glacier will collapse within five years, but that the ice shelf which rests on the ocean and restrains the eastern portion of the Thwaites Glacier. The floating ice shelf acts as a brace that prevents faster flow of the upstream ice. [31] This would mean an increased outflow from the glacier and thus an increased contribution to sea level rise by 66 cm (26 in) [1] (increasing from 4% of sea level rise to 5% of sea level rise in the short term). [7] [9] Under the hypothesis of marine ice cliff instability, the exposing of tall cliffs from the ice shelf's failure may lead to a chain reaction of collapse over centuries, [31] although the accuracy of this hypothesis has been disputed by other studies. [32] [33] [34]
According to Ted Scambos, a glaciologist at the University of Colorado Boulder and a leader of the International Thwaites Glacier Collaboration, in a late 2021 interview from McMurdo Station, "Things are evolving really rapidly here. It's daunting." [17] At a meeting of the American Geophysical Union in New Orleans, Louisiana in December, the situation was described as worrisome. [7] Fellow International Thwaites Glacier Collaboration glaciologist Erin Pettit noted in an interview with Science Magazine that Thwaites, along with the rest of the West Antarctic Ice Sheet, would start to see major losses "within decades" after the ice shelf's failure, and this would be especially pronounced if the anthropogenic emission trajectory does not decrease by then. In her own words: "We’ll start to see some of that before I leave this Earth." [10]
A 2022 assessment of tipping points in the climate system did not consider Thwaites Glacier on its own, but it did note that the entire West Antarctic Ice Sheet would most likely take 2,000 years to disintegrate entirely once it crosses its tipping point, and the minimum plausible timescale is 500 years. (And could even be as long as 13,000 years.) Yet, it also noted that this tipping point for the entire ice sheet is no more than 3 °C of global warming away, and is very likely to be triggered around the near-future levels of 1.5 °C: at worst, it may have even been triggered by now, after the warming passed 1 °C in the recent years. [35] [36]
The Thwaites Glacier Tongue, or Thwaites Ice Tongue ( 75°0′S106°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.
The Thwaites Iceberg Tongue ( 74°0′S108°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. [37] It was first noted in the 1930s, but finally detached from the ice tongue and broke up in the late 1980s. [38] [39]
In January 2019, NASA discovered an underwater cavity beneath the glacier, with an area two-thirds the size of Manhattan. The cavity formed mostly in the previous three years and is nearly 1,000 feet (305 m) tall, likely speeding up the glacier's decay. Thwaites currently contributes roughly 4% to global sea level rise. [40]
A 5-year international collaboration to study the Thwaites Glacier was established in 2018. [41] [42] [8]
At the beginning of 2020, researchers from the ITGC took measurements to develop scenarios for the future of the glacier and to predict the time frame for a possible collapse: The erosion of the glacier by warmed ocean water seems to be stronger than expected. The researchers noted with concern that, at the baseline of the glacier, the temperature of the water is already more than two degrees above freezing point. They confirm thawing of the Thwaites Glacier contributes about four percent of global sea-level rise. [8] The collapse of this glacier alone would raise the sea level by about 65 centimetres (25 inches). [43]
The climate of Antarctica is the coldest on Earth. The continent is also extremely dry, averaging 166 mm (6.5 in) of precipitation per year. Snow rarely melts on most parts of the continent, and, after being compressed, becomes the glacier ice that makes up the ice sheet. Weather fronts rarely penetrate far into the continent, because of the katabatic winds. Most of Antarctica has an ice-cap climate with very cold, generally extremely dry weather.
The Ross Ice Shelf is the largest ice shelf of Antarctica. It is several hundred metres thick. The nearly vertical ice front to the open sea is more than 600 kilometres (370 mi) long, and between 15 and 50 metres high above the water surface. Ninety percent of the floating ice, however, is below the water surface.
An ice shelf is a large floating platform of ice that forms where a glacier or ice sheet flows down to a coastline and onto the ocean surface. Ice shelves are only found in Antarctica, Greenland, Northern Canada, and the Russian Arctic. The boundary between the floating ice shelf and the anchor ice that feeds it is the grounding line. The thickness of ice shelves can range from about 100 m (330 ft) to 1,000 m (3,300 ft).
The Filchner-Ronne Ice Shelf, also known as Ronne-Filchner Ice Shelf, is an Antarctic ice shelf bordering the Weddell Sea.
The Amundsen Sea, an arm of the Southern Ocean off Marie Byrd Land in western Antarctica, lies between Cape Flying Fish 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.
The Western Antarctic Ice Sheet (WAIS) is the segment of the continental ice sheet that covers West Antarctica, the portion of Antarctica on the side of the Transantarctic Mountains that 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.
The Larsen Ice Shelf is a long ice shelf in the northwest part of the Weddell Sea, extending along the east coast of the Antarctic Peninsula from Cape Longing to Smith Peninsula. It is named after Captain Carl Anton Larsen, the master of the Norwegian whaling vessel Jason, who sailed along the ice front as far as 68°10' South during December 1893. In finer detail, the Larsen Ice Shelf is a series of shelves that occupy distinct embayments along the coast. From north to south, the segments are called Larsen A, Larsen B, and Larsen C by researchers who work in the area. Further south, Larsen D and the much smaller Larsen E, F and G are also named.
The Antarctic ice sheet is one of the two polar ice caps of Earth. It covers about 98% of the Antarctic continent and is the largest single mass of ice on Earth, with an average thickness of over 2 kilometers. It covers an area of almost 14 million square kilometres and contains 26.5 million cubic kilometres of ice. A cubic kilometer of ice weighs approximately 0.92 metric gigatonnes, meaning that the ice sheet weighs about 24,380,000 gigatonnes. It holds approximately 61% of all fresh water on Earth, equivalent to about 58 meters of sea level rise if all the ice were above sea level. In East Antarctica, the ice sheet rests on a major land mass, while in West Antarctica the bed can extend to more than 2,500 m below sea level.
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.
Denman Glacier is a glacier 11 to 16 km wide, descending north some 110 km (70 mi), which debouches into the Shackleton Ice Shelf east of David Island, Queen Mary Land. It was discovered in November 1912 by the Western Base party of the Australasian Antarctic Expedition under Sir Douglas Mawson. Mawson named the glacier for Lord Denman, Governor-General of Australia in 1911, a patron of the expedition.
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 retreat of glaciers since 1850 affects the availability of fresh water for irrigation and domestic use, mountain recreation, animals and plants that depend on glacier-melt, and, in the longer term, the level of the oceans. Deglaciation occurs naturally at the end of ice ages, but glaciologists find the current glacier retreat is accelerated by the measured increase of atmospheric greenhouse gases—an effect of climate change. Mid-latitude mountain ranges such as the Himalayas, Rockies, Alps, Cascades, Southern Alps, and the southern Andes, as well as isolated tropical summits such as Mount Kilimanjaro in Africa, are showing some of the largest proportionate glacial losses. Excluding peripheral glaciers of ice sheets, the total cumulated global glacial losses over the 26 year period from 1993–2018 were likely 5500 gigatons, or 210 gigatons per yr.
Totten Glacier is a large glacier draining a major portion of the East Antarctic Ice Sheet, through the Budd Coast of Wilkes Land in the Australian Antarctic Territory. The catchment drained by the glacier is estimated at 538,000 km2 (208,000 sq mi), extending approximately 1,100 km (680 mi) into the interior and holds the potential to raise sea level by at least 3.5 m (11 ft). Totten drains northeastward from the continental ice but turns northwestward at the coast where it terminates in a prominent tongue close east of Cape Waldron. It was first delineated from aerial photographs taken by USN Operation Highjump (1946–47), and named by Advisory Committee on Antarctic Names (US-ACAN) for George M. Totten, midshipman on USS Vincennes of the United States Exploring Expedition (1838–42), who assisted Lieutenant Charles Wilkes with correction of the survey data obtained by the expedition.
Ice sheet dynamics describe the motion within large bodies of ice, such those currently on Greenland and Antarctica. Ice motion is dominated by the movement of glaciers, whose gravity-driven activity is controlled by two main variable factors: the temperature and the strength of their bases. A number of processes alter these two factors, resulting in cyclic surges of activity interspersed with longer periods of inactivity, on both hourly and centennial time scales. Ice-sheet dynamics are of interest in modelling future sea level rise.
Between 1901 and 2018, the globally averaged sea level rose by 15–25 cm (6–10 in), or 1–2 mm per year on average. This rate is accelerating, and the sea levels are now rising by 3.7 mm per year. This is caused by human-induced climate change, as it continually heats the ocean and melts land-based ice sheets and glaciers. Over the period between 1993 and 2018, the thermal expansion of water contributed 42% to sea level rise ; melting of temperate glaciers, 21%; Greenland, 15%; and Antarctica, 8%. Because sea level rise lags changes in Earth temperature, it will continue to accelerate between now and 2050 purely in response to warming which has already occurred: whether it continues to accelerate after that is dependent on the human greenhouse gas emissions. Even if sea level rise does not accelerate, it will continue for a very long time: over the next 2000 years, it is projected to amount to 2–3 m (7–10 ft) if global warming is limited to 1.5 °C (2.7 °F), to 2–6 m (7–20 ft) if it peaks at 2 °C (3.6 °F) and to 19–22 metres (62–72 ft) if it peaks at 5 °C (9.0 °F).
Eric J. Rignot is a chancellor professor of Earth system science at the University of California, Irvine, and senior research scientist for the Radar Science and Engineering Section at NASA's Jet Propulsion Laboratory.
Helen Amanda Fricker is a glaciologist and professor at Scripps Institution of Oceanography at the University of California, San Diego where she is a director of the Scripps Polar Center. She won the 2010 Martha T. Muse Prize for Science and Policy in Antarctica.
Marine ice sheet instability (MISI) describes the potential for ice sheets grounded below sea level to destabilize in a runaway fashion. The mechanism was first proposed in the 1970s by Johannes Weertman and was quickly identified as a means by which even gradual anthropogenic warming could lead to relatively rapid sea level rise. In Antarctica, the West Antarctic Ice Sheet, the Aurora Subglacial Basin, and the Wilkes Basin are each grounded below sea level and are inherently subject to MISI.
Thwaites Ice Shelf, is an Antarctic ice shelf in the Amundsen Sea. It was named by ACAN after Fredrik T. Thwaites, a glacial geologist and geomorphologist. The Thwaites Ice Shelf is one of the biggest ice shelves in West Antarctica, though it is highly unstable and disintegrating rapidly. Since the 1980s, the Thwaites glacier, nicknamed the "Doomsday glacier", has had a net loss of over 600 billion tons of ice, though pinning of the Thwaites Ice Shelf has served to slow the process. The Thwaites Ice Shelf has acted like a dam for the eastern portion of glacier, bracing it and allowing for a slow melt rate, in contrast to the undefended western portion.
Kirsteen Jane Tinto is a glaciologist known for her research on the behavior and subglacial geology of the Greenland and Antarctic ice sheets.
Because Thwaites sits below sea level on ground that dips away from the coast, the warm water is likely to melt its way inland, beneath the glacier itself, freeing its underbelly from bedrock. A collapse of the entire glacier, which some researchers think is only centuries away, would raise global sea level by 65 centimeters.
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