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94-714: The British-Irish Ice Sheet (BIIS), also known as the Irish Sea Glacier was an ice sheet during the Pleistocene Ice Age that, probably on more than one occasion, flowed southwards from its source areas in Scotland and Ireland and across the Isle of Man , Anglesey and Pembrokeshire . It probably reached its maximum extent during the Anglian Glaciation , and it was also extensive during

188-487: A climate change feedback if it is gradually released through meltwater, thus increasing overall carbon dioxide emissions . For comparison, 1400–1650 billion tonnes are contained within the Arctic permafrost . Also for comparison, the annual human caused carbon dioxide emissions amount to around 40 billion tonnes of CO 2 . In Greenland, there is one known area, at Russell Glacier , where meltwater carbon

282-581: A 1 m tidal oscillation can be felt as much as 100 km from the sea. During larger spring tides , an ice stream will remain almost stationary for hours at a time, before a surge of around a foot in under an hour, just after the peak high tide; a stationary period then takes hold until another surge towards the middle or end of the falling tide. At neap tides, this interaction is less pronounced, and surges instead occur approximately every 12 hours. Increasing global air temperatures due to climate change take around 10,000 years to directly propagate through

376-425: A buttressing effect on the ice sheet, the so-called back stress increases and the grounding line is pushed backwards. The ice sheet is likely to start losing more ice from the new location of the grounding line and so become lighter and less capable of displacing seawater. This eventually pushes the grounding line back even further, creating a self-reinforcing mechanism . Because the entire West Antarctic Ice Sheet

470-580: A camp was operated at the Ford Ranges (FRD) in western Marie Byrd Land, supporting a part of a United States Antarctic Program (USAP) airborne survey initiated by UCSB and supported by the UTIG flying out of Siple Dome. In 2004–05, a large camp, Thwaites (THW) was established by the USAP 150 km (93 mi) north of NBY, in order to support a large airborne geophysical survey of eastern Marie Byrd Land by

564-587: A flat long profile would be difficult to explain. Tightly confined "valley glaciers" do not exist on open tundra situations (such as this must have been at the time) especially if the glacier bed rises southwards. Glacier ice in those circumstances must have "backed up" and spread sideways. It is most likely that when the Irish Sea Glacier reached its southernmost extent, the glacier surface must have been at c 2,000m in St George's Channel, c 2,250m over

658-482: A higher level of warming. Isostatic rebound of ice-free land may also add around 1 m (3 ft 3 in) to the global sea levels over another 1,000 years. The East Antarctic Ice Sheet (EAIS) lies between 45° west and 168° east longitudinally. It was first formed around 34 million years ago, and it is the largest ice sheet on the entire planet, with far greater volume than the Greenland ice sheet or

752-432: A much greater area than this minimum definition, measuring at 1.7 million km and 14 million km , respectively. Both ice sheets are also very thick, as they consist of a continuous ice layer with an average thickness of 2 km (1 mi). This ice layer forms because most of the snow which falls onto the ice sheet never melts, and is instead compressed by the mass of newer snow layers. This process of ice sheet growth

846-705: A portion of the ice sheet collapses. External factors might also play a role in forcing ice sheets. Dansgaard–Oeschger events are abrupt warmings of the northern hemisphere occurring over the space of perhaps 40 years. While these D–O events occur directly after each Heinrich event, they also occur more frequently – around every 1500 years; from this evidence, paleoclimatologists surmise that the same forcings may drive both Heinrich and D–O events. Hemispheric asynchrony in ice sheet behavior has been observed by linking short-term spikes of methane in Greenland ice cores and Antarctic ice cores. During Dansgaard–Oeschger events ,

940-488: A series of reference points and benchmarks throughout much of Marie Byrd Land during 1966–1968. USS  Glacier  (AGB-4) explored the parts of the Walgreen Coast and Eights Coast in 1960–61. It had parties of geologists and surveyors along that were deployed to outcrops on land. This expedition to the far eastern reaches of Marie Byrd Land determined that Thurston Peninsula as proposed by earlier expeditions

1034-460: A shallow fjord and stabilized) could have involved MICI, but there weren't enough observations to confirm or refute this theory. The retreat of Greenland ice sheet 's three largest glaciers - Jakobshavn , Helheim , and Kangerdlugssuaq Glacier - did not resemble predictions from ice cliff collapse at least up until the end of 2013, but an event observed at Helheim Glacier in August 2014 may fit

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1128-407: A worst-case of about 33 cm (13 in). For comparison, melting has so far contributed 1.4 cm ( 1 ⁄ 2  in) since 1972, while sea level rise from all sources was 15–25 cm (6–10 in) between 1901 and 2018. Historically, ice sheets were viewed as inert components of the carbon cycle and were largely disregarded in global models. In 2010s, research had demonstrated

1222-409: Is about 1 million years old. Due to anthropogenic greenhouse gas emissions , the ice sheet is now the warmest it has been in the past 1000 years, and is losing ice at the fastest rate in at least the past 12,000 years. Every summer, parts of the surface melt and ice cliffs calve into the sea. Normally the ice sheet would be replenished by winter snowfall, but due to global warming the ice sheet

1316-456: Is believed that the loss of the ice sheet would take place between 2,000 and 13,000 years in the future, although several centuries of high emissions may shorten this to 500 years. 3.3 m (10 ft 10 in) of sea level rise would occur if the ice sheet collapses but leaves ice caps on the mountains behind. Total sea level rise from West Antarctica increases to 4.3 m (14 ft 1 in) if they melt as well, but this would require

1410-468: Is evidence of large glaciers in Greenland for most of the past 18 million years, these ice bodies were probably similar to various smaller modern examples, such as Maniitsoq and Flade Isblink , which cover 76,000 and 100,000 square kilometres (29,000 and 39,000 sq mi) around the periphery. Conditions in Greenland were not initially suitable for a single coherent ice sheet to develop, but this began to change around 10 million years ago , during

1504-483: Is grounded below the sea level, it would be vulnerable to geologically rapid ice loss in this scenario. In particular, the Thwaites and Pine Island glaciers are most likely to be prone to MISI, and both glaciers have been rapidly thinning and accelerating in recent decades. As the result, sea level rise from the ice sheet could be accelerated by tens of centimeters within the 21st century alone. The majority of

1598-724: Is known to vary on seasonal to interannual timescales. The Wilkes Basin is the only major submarine basin in Antarctica that is not thought to be sensitive to warming. Ultimately, even geologically rapid sea level rise would still most likely require several millennia for the entirety of these ice masses (WAIS and the subglacial basins) to be lost. A related process known as Marine Ice Cliff Instability (MICI) posits that ice cliffs which exceed ~ 90 m ( 295 + 1 ⁄ 2  ft) in above-ground height and are ~ 800 m ( 2,624 + 1 ⁄ 2  ft) in basal (underground) height are likely to collapse under their own weight once

1692-501: Is melting two to five times faster than before 1850, and snowfall has not kept up since 1996. If the Paris Agreement goal of staying below 2 °C (3.6 °F) is achieved, melting of Greenland ice alone would still add around 6 cm ( 2 + 1 ⁄ 2  in) to global sea level rise by the end of the century. If there are no reductions in emissions, melting would add around 13 cm (5 in) by 2100, with

1786-487: Is released into the atmosphere as methane , which has a much larger global warming potential than carbon dioxide. However, it also harbours large numbers of methanotrophic bacteria, which limit those emissions. Normally, the transitions between glacial and interglacial states are governed by Milankovitch cycles , which are patterns in insolation (the amount of sunlight reaching the Earth). These patterns are caused by

1880-589: Is smaller. Prominent ranges include the Ford Ranges in western MBL, The Flood Range , the Executive Committee Range, and the Kohler Range . The Ford Ranges are the most extensive and include more than six individual named mountain groups. The Executive Committee Range includes five volcanoes, some proposed to be dormant or active. The Flood Range comprises a linear chain of Neogene and Quaternary age volcanoes. The Fosdick mountains in

1974-484: Is still occurring nowadays, as can be clearly seen in an example that occurred in World War II . A Lockheed P-38 Lightning fighter plane crashed in Greenland in 1942. It was only recovered 50 years later. By then, it had been buried under 81 m (268 feet) of ice which had formed over that time period. Even stable ice sheets are continually in motion as the ice gradually flows outward from the central plateau, which

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2068-524: Is still open for debate. The icing of Antarctica began in the Late Palaeocene or middle Eocene between 60 and 45.5 million years ago and escalated during the Eocene–Oligocene extinction event about 34 million years ago. CO 2 levels were then about 760 ppm and had been decreasing from earlier levels in the thousands of ppm. Carbon dioxide decrease, with a tipping point of 600 ppm,

2162-680: Is the Russian station Russkaya , which was occupied 1980–1990 and is now closed. East of the Siple Coast off the Ross Ice Shelf, Siple Dome was established as a summer science camp in 1996. Ice cores have been drilled here to retrieve the climate history of the last 100,000 years. This camp also served as a base for airborne geophysical surveys supported by the University of Texas Institute for Geophysics (UTIG). In 1998–1999,

2256-702: Is the largest unclaimed territory on Earth. It was named after the wife of American naval officer Richard E. Byrd , who explored the region in the early 20th century. The territory lies in West Antarctica , east of the Ross Ice Shelf and the Ross Sea and south of the Pacific Ocean portion of the Antarctic or Southern Ocean , extending eastward approximately to a line between the head of

2350-644: 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 . It 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

2444-577: Is the tallest point of the ice sheet, and towards the margins. The ice sheet slope is low around the plateau but increases steeply at the margins. Increasing global air temperatures due to climate change take around 10,000 years to directly propagate through the ice before they influence bed temperatures, but may have an effect through increased surface melting, producing more supraglacial lakes . These lakes may feed warm water to glacial bases and facilitate glacial motion. In previous geologic time spans ( glacial periods ) there were other ice sheets. During

2538-456: Is the tallest point of the ice sheet, and towards the margins. The ice sheet slope is low around the plateau but increases steeply at the margins. This difference in slope occurs due to an imbalance between high ice accumulation in the central plateau and lower accumulation, as well as higher ablation , at the margins. This imbalance increases the shear stress on a glacier until it begins to flow. The flow velocity and deformation will increase as

2632-512: The Amundsen Sea . As a smaller part of Antarctica, WAIS is also more strongly affected by climate change . There has been warming over the ice sheet since the 1950s, and a substantial retreat of its coastal glaciers since at least the 1990s. Estimates suggest it added around 7.6 ± 3.9 mm ( 19 ⁄ 64  ±  5 ⁄ 32  in) to the global sea level rise between 1992 and 2017, and has been losing ice in

2726-633: The Bindschadler and Whillans ice streams are the most extensive. The seven ice streams discharge 40 percent of the WAIS. Besides the Ross Ice Shelf, significant ice shelves on the coast of the Southern Ocean include the Sulzberger , and Nickerson . Due to the burial of the continental basement of MBL by the WAIS, mountain ranges are exposed towards the coast of MBL where ice thickness

2820-638: The Fosdick Mountains in 1934. Aerial exploration discovered lands farther east along the Ruppert Coast . The Third Byrd Antarctic Expedition, also called the United States Antarctic Service Expedition , took place from 1939 to 1941. This expedition established two base camps 2,600 kilometres (1,600 miles) apart. West Base was near the former Little America base (68° 29' S, 163° 57' W) and East Base

2914-659: The International Geophysical Year (IGY; from July 1957 to end of 1958) that saw several exploratory overland traverses with tractor trains ( Sno-cats and modified bulldozers ). Starting in January 1957 (pre-IGY) Charles R. Bentley led a traverse from Little America V to the new Byrd station along the route blazed by United States Army engineers a few months before (the Army-Navy Drive ). His team conducted measurements of ice thickness and of

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3008-713: The Last Glacial Period at Last Glacial Maximum , the Laurentide Ice Sheet covered much of North America . In the same period, the Weichselian ice sheet covered Northern Europe and the Patagonian Ice Sheet covered southern South America . An ice sheet is a body of ice which covers a land area of continental size - meaning that it exceeds 50,000 km . The currently existing two ice sheets in Greenland and Antarctica have

3102-691: The Ross Ice Shelf and Eights Coast . It stretches between 158°W and 103°24'W. The inclusion of the area between the Rockefeller Plateau and Eights Coast is based upon Byrd's exploration. Because of its remoteness, even by Antarctic standards, most of Marie Byrd Land (the portion east of 150°W) has not been claimed by any sovereign state . It is by far the largest single unclaimed territory on Earth , with an area of 1,610,000 km (620,000 sq mi), including Eights Coast , immediately east of Marie Byrd Land. In 1939, United States President Franklin D. Roosevelt instructed members of

3196-538: The United States Antarctic Service Expedition to take steps to claim some of Antarctica as United States territory. Although this appears to have been done by members of this and subsequent expeditions, these do not appear to have been formalized prior to 1959, when the Antarctic Treaty System was set up. Some publications in the United States have shown this as a United States territory in

3290-644: The West Antarctic Ice Sheet (WAIS), from which it is separated by the Transantarctic Mountains . The ice sheet is around 2.2 km (1.4 mi) thick on average and is 4,897 m (16,066 ft) at its thickest point. It is also home to the geographic South Pole , South Magnetic Pole and the Amundsen–Scott South Pole Station . The surface of the EAIS is the driest, windiest, and coldest place on Earth. Lack of moisture in

3384-551: The Younger Dryas period which appears consistent with MICI. However, it indicates "relatively rapid" yet still prolonged ice sheet retreat, with a movement of >200 km (120 mi) inland taking place over an estimated 1100 years (from ~12,300 years Before Present to ~11,200 B.P.) In recent years, 2002-2004 fast retreat of Crane Glacier immediately after the collapse of the Larsen B ice shelf (before it reached

3478-555: The 2010s at a rate equivalent to 0.4 millimetres (0.016 inches) of annual sea level rise. While some of its losses are offset by the growth of the East Antarctic ice sheet , Antarctica as a whole will most likely lose enough ice by 2100 to add 11 cm (4.3 in) to sea levels. Further, marine ice sheet instability may increase this amount by tens of centimeters, particularly under high warming. Fresh meltwater from WAIS also contributes to ocean stratification and dilutes

3572-473: The Amundsen Sea. It entails marine, airborne, and on-ice geophysical exploration that will illuminate the character of Marie Byrd Land bedrock geology and the nature of the eastern boundary of the province. The goal is determining the stability of the glacier and prediction of global sea level rise from shrinking of the WAIS. Adjacent to the continent, Marie Byrd Land is bordered by the Amundsen Sea in

3666-732: The Anglian Glaciation, the ice spread out into a great lobe, in the area now occupied by the Celtic Sea and the approaches to the Bristol Channel . On the eastern flank of the glacier, the evidence of striations, glacial deposits and "erratic trains" shows that the edge of the Irish Sea Glacier was pushed southwards by ice coming from the Welsh ice cap on the Brecon Beacons, so that Irish Sea ice flowed parallel with

3760-502: The Antarctic winter is cooler at the surface than in its middle layers. Consequently, greenhouse gases actually trap heat in the middle atmosphere and reduce its flow towards the surface while the temperature inversion lasts. Due to these factors, East Antarctica had experienced slight cooling for decades while the rest of the world warmed as the result of climate change . Clear warming over East Antarctica only started to occur since

3854-710: The Earth's magnetic and gravity field. The following summer season (1957–58) he led a second traverse out of Byrd Station that visited volcanoes of the Marie Byrd Land Volcanic Province for the first time. The traverse reached the Sentinel Mountains beyond eastern Marie Byrd Land before returning to Byrd Station. Bentley led a third traverse out of Byrd Station to the Horlick Mountains in 1958–59. These three traverses led to

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3948-510: The East Antarctic Ice Sheet would not be affected. Totten Glacier is the largest glacier there which is known to be subject to MISI - yet, its potential contribution to sea level rise is comparable to that of the entire West Antarctic Ice Sheet. Totten Glacier has been losing mass nearly monotonically in recent decades, suggesting rapid retreat is possible in the near future, although the dynamic behavior of Totten Ice Shelf

4042-708: The Fosdick Mountains. The United States Navy mounted several expeditions to Antarctica in the period 1946 to 1959. These expeditions ( Operation Highjump led by R. E. Byrd, Windmill , and Deep Freeze I–IV) included aerial photography using the Trimetrogon system of aerial photographs (TMA; vertical, left, and right oblique images over the same point) over portions of coastal Marie Byrd Land. The U.S. Navy began construction of Byrd Station at 80°S, 120°W with traverses out of Little America V in 1956–57 during Deep Freeze II. These efforts were in advance of

4136-669: The Isle of Anglesey, and c 2,500m over the Isle of Man. It follows that the mountains of Wales and Eastern Ireland must also have been submerged beneath thick glacier ice at the time. Furthermore, the Bristol Channel is most likely to have been ice-filled at the LGM, as indicated on the adjoining map. A 2007 study suggests that the area outside the South Ireland End Moraine was inundated by Irish Ice during and after

4230-630: The LGM. At the same time parts of the area outside the South Wales End Moraine must also have been inundated by ice. Another puzzle is the extent to which the long profile of the Irish Sea Glacier, at the time of its maximum extent, approximated to the classic equilibrium profile. Work in analogous situations in Marie Byrd Land , Antarctica , suggests that the ice surface altitude over the mountains might have been around 800m lower than predicted. Ice sheet Although

4324-550: The Late Devensian Glaciation (or Last Glacial Maximum ). It was the only clearly defined major glacier in the Irish Sea and flowed about 700 km from its source areas to its southernmost margin. It is sometimes referred to as an “ice stream” since it appears to have been constrained not by ice-free land areas but by highlands which were themselves buried beneath ice. At the time of its maximum extent

4418-719: The Marie Byrd Land Dome. A digital map of Antarctica includes the geology of Marie Byrd Land. The geologic history of Marie Byrd Land in West Antarctica was summarized in a 2020 publication. Prominent glaciers that drain the WAIS in MBL include the Thwaites, and also the Pine Island Glacier , both of which empty into the Amundsen Sea. Of the seven ice streams that drain into the Ross Ice Shelf,

4512-640: The Ross Sea. The far western coast of Marie Byrd Land was seen from the decks of Robert Falcon Scott 's ship Discovery in 1902. He named the peninsula adjacent to the Ross Sea King Edward VII Land and the scattered outcrops that were within sight, the Alexandra Mountains . In 1911, during Roald Amundsen 's South Pole expedition, Kristian Prestrud led a sledge party that visited these isolated outcrops ( nunataks ) in

4606-656: The SLR was greater than 6 m ( 19 + 1 ⁄ 2  ft). As of 2023, the most recent analysis indicates that the Last Interglacial SLR is unlikely to have been higher than 2.7 m (9 ft), as higher values in other research, such as 5.7 m ( 18 + 1 ⁄ 2  ft), appear inconsistent with the new paleoclimate data from The Bahamas and the known history of the Greenland Ice Sheet. The West Antarctic Ice Sheet (WAIS)

4700-664: The UTIG. In 2006, a major encampment, WAIS Divide (WSD) was established on the divide between the Ross Sea Embayment and the Amundsen Sea Embayment, in the easternmost portion of Marie Byrd Land, in order to drill a high resolution ice core . Drilling and coring ended in 2014. In 2018, the International Thwaites Glacier Collaboration commenced with a large and ongoing physical presence onshore of

4794-506: The WAIS have been proposed to follow rift valleys , now buried by ice, which formed in the WARS. The WARS contains a volcanic province with volcanoes active from the Eocene epoch to a few thousand years ago. A mantle plume was discovered deep below Marie Byrd Land. Heat from the plume has been proposed responsible for uplift of a significant portion of West Antarctica to form

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4888-412: The air, high albedo from the snow as well as the surface's consistently high elevation results in the reported cold temperature records of nearly −100 °C (−148 °F). It is the only place on Earth cold enough for atmospheric temperature inversion to occur consistently. That is, while the atmosphere is typically warmest near the surface and becomes cooler at greater elevation, atmosphere during

4982-416: The base of the glacier in as little as 2–18 hours – lubricating the bed and causing the glacier to surge . Water that reaches the bed of a glacier may freeze there, increasing the thickness of the glacier by pushing it up from below. As the margins end at the marine boundary, excess ice is discharged through ice streams or outlet glaciers . Then, it either falls directly into the sea or is accumulated atop

5076-427: The boulders and other continental rocks they carried, leaving layers known as ice rafted debris . These so-called Heinrich events , named after their discoverer Hartmut Heinrich , appear to have a 7,000–10,000-year periodicity , and occur during cold periods within the last interglacial. Internal ice sheet "binge-purge" cycles may be responsible for the observed effects, where the ice builds to unstable levels, then

5170-664: The coast of South Wales and then came into contact with the English coast around the Somerset Levels, between Exmoor and the Mendips. It is not known how far inland this ice extended, but there are scattered glacial deposits in the Bridgwater - Glastonbury district—these may mark the easternmost extent of the glacier. On its western flank the Irish Sea Glacier reached Cork Harbour. The maximum width of this great ice lobe

5264-402: The collapse of Larsen B, in context. In the 1970s, Johannes Weertman proposed that because seawater is denser than ice, then any ice sheets grounded below sea level inherently become less stable as they melt due to Archimedes' principle . Effectively, these marine ice sheets must have enough mass to exceed the mass of the seawater displaced by the ice, which requires excess thickness. As

5358-515: The continent since the 1957. The Greenland ice sheet is an ice sheet which forms the second largest body of ice in the world. It is an average of 1.67 km (1.0 mi) thick, and over 3 km (1.9 mi) thick at its maximum. It is almost 2,900 kilometres (1,800 mi) long in a north–south direction, with a maximum width of 1,100 kilometres (680 mi) at a latitude of 77°N , near its northern edge. The ice sheet covers 1,710,000 square kilometres (660,000 sq mi), around 80% of

5452-505: The definition. Further, modelling done after the initial hypothesis indicates that ice-cliff instability would require implausibly fast ice shelf collapse (i.e. within an hour for ~ 90 m ( 295 + 1 ⁄ 2  ft)-tall cliffs), unless the ice had already been substantially damaged beforehand. Further, ice cliff breakdown would produce a large number of debris in the coastal waters - known as ice mélange - and multiple studies indicate their build-up would slow or even outright stop

5546-425: The discovery of the Bentley Subglacial Trench or Trough, a deep bedrock chasm between MBL and the Transantarctic Mountains of East Antarctica. During 1958–1960 TMA flights and a traverse out of Byrd Station visited and mapped the Executive Committee Range. TMA were flown in western Marie Byrd Land in 1964 and 1965. Following these efforts the United States Geological Survey (USGS) mounted land surveys to establish

5640-408: The discovery of the Rockefeller Mountains and the Edsel Ford Ranges farther to the east. Byrd named the region after his wife Marie. A geological party led by L. Gould briefly explored parts of the Rockefeller Mountains. The first deep overland exploration occurred during the second Byrd expedition (1933–1935) when a sledge party led by Paul Siple and Franklin Alton Wade reached as far east as

5734-416: The east and the Ross Sea and Ross Ice Shelf in the west. Mountain ranges are prominent along and near the coastline with a few exceptions. Marie Byrd Land is covered by the vast West Antarctic Ice Sheet (WAIS). The WAIS in Marie Byrd Land drains off the continent to the east into the Ross Ice Shelf via seven ice streams . Along the coast of the Southern Ocean and the Amundsen Sea, ice drains via glaciers,

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5828-522: The equilibrium line between these two processes is approached. This motion is driven by gravity but is controlled by temperature and the strength of individual glacier bases. A number of processes alter these two factors, resulting in cyclic surges of activity interspersed with longer periods of inactivity, on time scales ranging from hourly (i.e. tidal flows) to the centennial (Milankovich cycles). On an unrelated hour-to-hour basis, surges of ice motion can be modulated by tidal activity. The influence of

5922-498: The existence of uniquely adapted microbial communities , high rates of biogeochemical and physical weathering in ice sheets, and storage and cycling of organic carbon in excess of 100 billion tonnes. There is a massive contrast in carbon storage between the two ice sheets. While only about 0.5-27 billion tonnes of pure carbon are present underneath the Greenland ice sheet, 6000-21,000 billion tonnes of pure carbon are thought to be located underneath Antarctica. This carbon can act as

6016-406: The floating ice shelves . Those ice shelves then calve icebergs at their periphery if they experience excess of ice. Ice shelves would also experience accelerated calving due to basal melting. In Antarctica, this is driven by heat fed to the shelf by the circumpolar deep water current, which is 3 °C above the ice's melting point. The presence of ice shelves has a stabilizing influence on

6110-399: The formation of salty Antarctic bottom water , which destabilizes Southern Ocean overturning circulation . In the long term, the West Antarctic Ice Sheet is likely to disappear due to the warming which has already occurred. Paleoclimate evidence suggests that this has already happened during the Eemian period, when the global temperatures were similar to the early 21st century. It

6204-403: The glacier behind them, while an absence of an ice shelf becomes destabilizing. For instance, when Larsen B ice shelf in the Antarctic Peninsula had collapsed over three weeks in February 2002, the four glaciers behind it - Crane Glacier , Green Glacier , Hektoria Glacier and Jorum Glacier - all started to flow at a much faster rate, while the two glaciers (Flask and Leppard) stabilized by

6298-423: The glacier extended all the way to the coasts of Somerset and Cornwall, along the south coast of Ireland, and even reached the Isles of Scilly . It was forced through a relatively narrow constriction in St George's Channel by ice flowing from the Irish Ice Cap (to the west) and the Welsh Ice Cap (to the east). At one point the glacier was probably no more than 80 km wide. Once through this constriction, in

6392-521: The hinterland of Bakutis Coast . Byrd Station was the only major base in the interior of West Antarctica for many years. In 1968, the first ice core to fully penetrate the Antarctic Ice Sheet was drilled here. The year-round station was abandoned in 1972, and after operating for years as a temporary summer encampment, Byrd Surface Camp, Byrd Station was reopened by the United States Antarctic Program (USAP) in 2009–2010 to support operations in northern West Antarctica. On Ruppert Coast of Marie Byrd Land

6486-437: The ice before they influence bed temperatures, but may have an effect through increased surface melting, producing more supraglacial lakes . These lakes may feed warm water to glacial bases and facilitate glacial motion. Lakes of a diameter greater than ~300 m are capable of creating a fluid-filled crevasse to the glacier/bed interface. When these crevasses form, the entirety of the lake's (relatively warm) contents can reach

6580-407: The ice of the Irish Sea Glacier also swept along the southern Irish coast as far west as Cork, and reached its outer limit about 100 km to the SW of the Isles of Scilly. Research suggests that the ice was grounded everywhere and not floating; this is consistent with the view that sea-level at the LGM was around 120m lower than it is today. Even further out in the southwest approaches, the ice edge

6674-415: The ice sheet melts and becomes thinner, the weight of the overlying ice decreases. At a certain point, sea water could force itself into the gaps which form at the base of the ice sheet, and marine ice sheet instability (MISI) would occur. Even if the ice sheet is grounded below the sea level, MISI cannot occur as long as there is a stable ice shelf in front of it. The boundary between the ice sheet and

6768-440: The ice shelf, known as the grounding line , is particularly stable if it is constrained in an embayment . In that case, the ice sheet may not be thinning at all, as the amount of ice flowing over the grounding line would be likely to match the annual accumulation of ice from snow upstream. Otherwise, ocean warming at the base of an ice shelf tends to thin it through basal melting. As the ice shelf becomes thinner, it exerts less of

6862-466: The instability soon after it started. Some scientists - including the originators of the hypothesis, Robert DeConto and David Pollard - have suggested that the best way to resolve the question would be to precisely determine sea level rise during the Last Interglacial . MICI can be effectively ruled out if SLR at the time was lower than 4 m (13 ft), while it is very likely if

6956-569: The intervening period, and the United States Department of Defense has stated that the United States has a solid basis for a claim in Antarctica resulting from its activities prior to 1959. The portion west of 150°W is part of Ross Dependency claimed by New Zealand . Five coastal areas are distinguished, which are listed from west to east: Marie Byrd Land was first explored from the west where it could be accessed from

7050-499: The major one being the Thwaites . West Antarctica and Marie Byrd Land have elevations of up to 1.5 to 2 kilometers on the surface of the WAIS. In contrast, East Antarctica has interior elevations on its ice sheet of over 4 kilometers. The West Antarctic Rift System (WARS ) that evolved over the last hundred million years, includes all or part of Marie Byrd Land. The WARS extends from the Ross Sea continental shelf east into Marie Byrd Land. The ice streams and glaciers that drain

7144-410: The middle Miocene , when the two passive continental margins which now form the uplands of West and East Greenland experienced uplift , and ultimately formed the upper planation surface at a height of 2000 to 3000 meter above sea level . Marie Byrd Land Marie Byrd Land ( MBL ) is an unclaimed region of Antarctica . With an area of 1,610,000 km (620,000 sq mi), it

7238-590: The mountain ranges within the northern Ford Ranges of Marie Byrd Land (FORCE expedition; Ford Ranges Crustal Exploration). GANOVEX VII a multinational expedition led by Germany visited Edward VII Peninsula in 1992–93. Colorado College geologists led expeditions to the Ford Ranges in 1998–2001 (Ford Ranges), 2005–2007 and 2011–2013 (Fosdick Mountains). Marie Byrd Land hosted the Operation Deep Freeze base Byrd Station (NBY; originally at 80°S, 120°W, rebuilt at 80°S, 119°W), beginning in 1957, in

7332-586: The northern Ford Ranges are a 30-kilometer-long span of Cretaceous metamorphic rocks. Most other exposed rock in MBL is Paleozoic metamorphosed sedimentary rock and granitoid , and Mesozoic granitoid. Away from the coasts, the WAIS buries individual mountains and ranges that are not named, the exception being major features such as the Bentley Subglacial Trench. Marie Byrd Seamount ( 70°0′S 118°0′W  /  70.000°S 118.000°W  / -70.000; -118.000 )

7426-475: The northern hemisphere warmed considerably, dramatically increasing the release of methane from wetlands, that were otherwise tundra during glacial times. This methane quickly distributes evenly across the globe, becoming incorporated in Antarctic and Greenland ice. With this tie, paleoclimatologists have been able to say that the ice sheets on Greenland only began to warm after the Antarctic ice sheet had been warming for several thousand years. Why this pattern occurs

7520-415: The peripheral ice stabilizing them is gone. Their collapse then exposes the ice masses following them to the same instability, potentially resulting in a self-sustaining cycle of cliff collapse and rapid ice sheet retreat - i.e. sea level rise of a meter or more by 2100 from Antarctica alone. This theory had been highly influential - in a 2020 survey of 106 experts, the paper which had advanced this theory

7614-469: The region bordering the eastern Ross Sea and Ross Ice Shelf. At the same time the first Japanese Antarctic Expedition led by Nobu Shirase landed a shore party on the peninsula. Dean Smith was the pilot during aerial overflights in 1929 with Richard E. Byrd's first Antarctic expedition (1928–1930). It originated from Little America near Amundsen's original base camp Framheim in the Bay of Whales, led to

7708-569: The remnants of the ice shelf did not accelerate. The collapse of the Larsen B shelf was preceded by thinning of just 1 metre per year, while some other Antarctic ice shelves have displayed thinning of tens of metres per year. Further, increased ocean temperatures of 1 °C may lead to up to 10 metres per year of basal melting. Ice shelves are always stable under mean annual temperatures of −9 °C, but never stable above −5 °C; this places regional warming of 1.5 °C, as preceded

7802-403: The surface is cold, the base of an ice sheet is generally warmer due to geothermal heat. In places, melting occurs and the melt-water lubricates the ice sheet so that it flows more rapidly. This process produces fast-flowing channels in the ice sheet — these are ice streams . Even stable ice sheets are continually in motion as the ice gradually flows outward from the central plateau, which

7896-448: The surface of Greenland , or about 12% of the area of the Antarctic ice sheet . The term 'Greenland ice sheet' is often shortened to GIS or GrIS in scientific literature . Greenland has had major glaciers and ice caps for at least 18 million years, but a single ice sheet first covered most of the island some 2.6 million years ago. Since then, it has both grown and contracted significantly. The oldest known ice on Greenland

7990-535: The variations in shape of the Earth's orbit and its angle relative to the Sun, caused by the gravitational pull of other planets as they go through their own orbits. For instance, during at least the last 100,000 years, portions of the ice sheet covering much of North America, the Laurentide Ice Sheet broke apart sending large flotillas of icebergs into the North Atlantic. When these icebergs melted they dropped

8084-529: The volcanic province during the period 1989–1991. The SPRITE project (South Pacific Rim International Tectonic Expedition) explored regions and surroundings of the Hobbs Coast in 1990–1993. Members of both projects were from the U.S., Britain, and New Zealand. During the Austral summers of 1989–1990 and 1990–1991, a geological party from the University of California, Santa Barbara (UCSB) explored several of

8178-460: The year 2000, and was not conclusively detected until the 2020s. In the early 2000s, cooling over East Antarctica seemingly outweighing warming over the rest of the continent was frequently misinterpreted by the media and occasionally used as an argument for climate change denial . After 2009, improvements in Antarctica's instrumental temperature record have proven that the warming over West Antarctica resulted in consistent net warming across

8272-457: Was a complex expedition involving remote helicopter camps and airborne geophysics. Several geological expeditions explored Marie Byrd Land during the period 1978–1993. New Zealand geologists surveyed the Ford Ranges and Edward VII Peninsula in two expeditions, 1978–79 and 1987–88. Exploration of the Marie Byrd Land Volcanic Province began in earnest by U.S. geologists in 1984–85. The WAVE project (West Antarctic Volcano Exploration ) focused on

8366-822: Was considered more important than even the year 2014 IPCC Fifth Assessment Report . Sea level rise projections which involve MICI are much larger than the others, particularly under high warming rate. At the same time, this theory has also been highly controversial. It was originally proposed in order to describe how the large sea level rise during the Pliocene and the Last Interglacial could have occurred - yet more recent research found that these sea level rise episodes can be explained without any ice cliff instability taking place. Research in Pine Island Bay in West Antarctica (the location of Thwaites and Pine Island Glacier ) had found seabed gouging by ice from

8460-411: Was floating and calving. One current theory is that the glacier moved to its outermost position by a "lobate surge partially propagated by high porewater pressures within deformable marine substrate", leaving parts of South Wales, the Bristol Channel and the coasts of SW England free of glacier ice. However, glaciers have to behave according to the laws of ice physics, and a long narrow lobate surge with

8554-520: Was in fact an island ( Thurston Island ). In the same season a geological party led by Campbell Craddock explored the Jones Mountains in the adjacent region. The United States Byrd Coastal Survey during 1966–1969, led by F. A. Wade, conducted geologic mapping of the Alexandra and Rockefeller Mountains and the Ford Ranges and produced a series of 1:250,000 geologic maps of the region. This

8648-671: Was more than 320 km. "Old" glacial deposits in South wales and in Pembrokeshire are still not accurately dated. Currently there is a great debate about the dating of the Devensian glaciation of the Isles of Scilly . The ice of the Irish Sea Glacier certainly pressed against the northern coasts of the islands, and accumulating evidence seems to show that this occurred some time after 24,000 years ago. During this same glacial episode

8742-633: Was near the Antarctic Peninsula on Stonington Island (68° 12' S, 67° 3' W). Exploration flights out of these two bases led to the discovery of most of the Marie Byrd Land Volcanic Province (e.g. Executive Committee Range ) and much of the coastal region including the Walgreen, Hobbs, and Ruppert Coasts. During the expedition trail parties from West Base visited the northern Ford Ranges and south slopes of

8836-527: Was the primary agent forcing Antarctic glaciation. The glaciation was favored by an interval when the Earth's orbit favored cool summers but oxygen isotope ratio cycle marker changes were too large to be explained by Antarctic ice-sheet growth alone indicating an ice age of some size. The opening of the Drake Passage may have played a role as well though models of the changes suggest declining CO 2 levels to have been more important. While there

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