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74-469: Erebus Glacier Tongue is about 10 metres (33 ft) high and is centred upon 77.6 degrees south latitude, 166.75 degrees east longitude. The portion of the glacier tongue extending beyond the shoreline or grounding line floats upon the water. Ice tongues emerge when a glacier ice stream flows rapidly (relative to surrounding ice) into the sea or a lake, usually in a protected area. For instance, Capes Evans and Royds extending from Ross Island protect

148-483: 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

222-581: 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

296-577: A 4 km section broke off during a gale. A similar event in March 1990 produced a 100-million ton iceberg, 3.5 km long, from the glacier tongue. In addition, observers note that the glacier tongue experienced a major calving event in the early 1940s. Such calving along the glacier snout naturally leads to shortening, while icebergs released from the glacier tongue sides contribute to the glacier's narrowing. The Erebus Glacier Tongue produces flat-topped or tabular icebergs. It calved most recently in 2013, around

370-425: 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

444-542: A cave that will safely hold all 10 of us. With childlike enthusiasm we explore the glacial cathedral with walls of deep blue ice. Breaking off pieces of ice, 10 or 20,000 years old, we melt it in our mouths and savour the taste of pure, uncontaminated water. Scientists funded by a National Science Foundation grant have retrieved rare underwater views of the Erebus Glacier Tongue caves by mounting cameras on Weddell seals . Images revealed rocks and dead fish frozen into

518-447: A decade earlier than expected. 77°44′03″S 166°31′41″E  /  77.7341°S 166.528°E  / -77.7341; 166.528 Ice tongue An ice tongue or glacier tongue exists when there is a narrow floating part of a glacier that extends out into a body of water beyond the glacier's lowest contact with the Earth's crust . An ice tongue forms when a glacier that

592-477: 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

666-432: 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

740-466: A narrow tunnel several hundred feet long to emerge into a large cavern describe their Erebus Glacier Tongue experience as: Sitting quietly we absorb the natural beauty. Suddenly, we hear the low grinding noise of the glacier moving and the three of us instinctively look at the narrow opening. Without saying a word we realize that it wouldn’t take much for the entrance to collapse and become sealed and trap us here. One by one we slowly exit. Steve later finds

814-700: 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 ,

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888-456: 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

962-407: 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

1036-399: Is a dynamic structure subject to a host of internal and external stresses which affect its shape, size, and durability. The frozen sea ice of Erebus Bay surrounding the Erebus Glacier Tongue typically breaks out during the summer. This exposes the glacier tongue to pounding waves from McMurdo Sound . Moreover, such wave action also impacts the ice caves accessed along the leading edges of

1110-409: 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

1184-456: 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

1258-493: Is confined by a valley moves very rapidly out into a lake or ocean, relative to other ice along the coastline. When such ice surges past adjacent coastal ice, the boundary experiences physical forces described as "shearing". Ice tongues can gain mass from water freezing at their base, by snow falling on top of them, or by additional surges from the main glacier. Mass is then lost by calving or by melting. Icebergs are often formed when ice tongues break off in part or wholly from

1332-468: 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

1406-478: 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

1480-718: 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

1554-494: 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

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1628-483: 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

1702-478: 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

1776-517: 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,

1850-675: 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

1924-456: 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

1998-506: 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

2072-451: The Antarctic ice sheet and the Greenland ice sheet . Ice sheets are bigger than ice shelves or alpine glaciers . Masses of ice covering less than 50,000 km are termed an ice cap . An ice cap will typically feed a series of glaciers around its periphery. Although the surface is cold, the base of an ice sheet is generally warmer due to geothermal heat. In places, melting occurs and

2146-680: 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

2220-467: The Marsden Fund supported deployment of Timothy Haskell's sea ice camp right next to the tongue. Observations from the camp showed how the tide flowed beneath and along the tongue and was affected by submarine topography. The forces of wave action from McMurdo Sound , tides, and internal stresses exploit the glacier tongue's weaknesses. Subsequently, small icebergs and bergy bits typically calf from

2294-630: 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

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2368-540: 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

2442-548: 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

2516-497: 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

2590-494: The Earth's topography at the bottom of the glacier also slows the ice stream. However, just the opposite occurs with basal sliding . Such sliding features the glacier jerking forward due to lubrication from bottom melt-water. Ice streams such as the Erebus Glacier Tongue wax and wane like the moon. Indeed, British researchers in 2006 discovered a correlation between lunar tides (caused by gravitational pull) and variances in flow speed of

2664-500: 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

2738-427: The Erebus Glacier Tongue but only when the sea ice has broken up. Subsequently, iceberg calving is seasonal and periodic, as open water is needed to release the bergs into Erebus Bay. Waters at the glacier tongue that receive the icebergs vary in depth from a minimum of 155–475 metres (509–1,558 ft). Members of Robert F. Scott's Terra Nova Expedition first observed the glacier tongue calving in March 1911 when

2812-503: The Erebus Glacier Tongue from the open waters of the Ross Sea . Hut Point Peninsula to the south helps deflect icebergs propelled by prevailing southerly winds. The long, narrow Erebus ice stream drains from the western slope of Mount Erebus , an active volcano rising 3,794 metres (12,448 ft) in elevation. The mountain constantly replenishes the glacial ice stream, as annual snow fall exceeds annual snow melt. The Erebus Glacier Tongue

2886-415: The Erebus Glacier Tongue, which ranges from 50 to 300 meters thick, contain smaller streams of ice. Each ice flow produces its own set of stress fields. Thus, throughout the glacier tongue, different flow rates and tensions are present. Stress and friction increase along the flanks of ice streams such as the Erebus Glacier Tongue. Stress appears as crevasses as the ice flow rate is slowed. Friction created by

2960-463: The Rutland Ice Stream in Antarctica. Previously a team of U.S. NASA, Penn State, and University of Newcastle; Newcastle upon Tyne, England; made similar observations of Whillan's Ice Stream in Antarctica. However, more established research unrelated to lunar forces is available regarding cyclical glacier growth and decay. Such research reveals that glacier growth can produce slow-motion surges in

3034-635: 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)

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3108-412: 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

3182-416: 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

3256-427: 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

3330-402: 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

3404-515: 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

3478-505: 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

3552-522: 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

3626-498: 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

3700-406: 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

3774-514: 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

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3848-515: 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

3922-506: The glacier tongue become unstable, rupture, and calve icebergs. Such instability in part comes from the flexing and tension the ice beam undergoes from being cantilevered over the sea. Moreover, the river of ice carries with it weaknesses introduced by earlier fractures experienced during its journey down the slopes of Mount Erebus . The floating glacier has a major effect on the local ocean. Its melting has been thought to create Double diffusive convection effects. A 2010 expedition funded by

3996-523: The glacier tongue. The ice caves include inter-locked crevasses covered by snow bridges . The ice caves are a popular attraction for residents from nearby the McMurdo Station and Scott Base research stations. Visitors report observing stalactite -like icicles on the cave ceilings, as well as intricate ice crystals. Sunlight filtering through ice into the caves bathes the interiors with diffuse blue light. Contemporary cave explorers who squeezed through

4070-414: The glacier's movement. Such surges may occur over a period of months or years. Then the movement stops. Scientists have measured Erebus Glacier Tongue's length as growing about 160 meters yearly. The Erebus Glacier Tongue flow pushes the glacier into Erebus Bay where it butts against seasonal ice pack. This massive but gradual collision of ice against ice creates pressure ridges in the glacier. Portions of

4144-437: 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

4218-415: 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

4292-440: 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

4366-477: The ice. Video also depicted other Weddell seals that appeared to use the underwater caves as hiding places from predators such as the orca (or killer whale) and the leopard seal . Weddell seals are commonly sighted by visitors to the Erebus Glacier Tongue. Each year 300 to 400 Weddell seal pups are born to a colony of seals that live in adjoining Erebus Bay. The seals have been distinctively marked and re-sighted since 1969. The nearly 40-year study represents one of

4440-458: 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

4514-462: The longest field investigations of its type, according to a Montana State University report. Emperor and Adelie penguins are also found in the vicinity of the Erebus Glacier Tongue. Adelie are particularly noted for their rookeries on Erebus Bay's rocky north shore at nearby Cape Royds . Penguins, like the Weddell seal, are preyed upon by orcas and leopard seals. The presence of penguins also attracts

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4588-543: The main glacier. A few examples of ice tongues are the Erebus Glacier Tongue , Drygalski Ice Tongue , and Thwaites Ice Tongue . This glaciology article is a stub . You can help Misplaced Pages by expanding it . Ice sheet dynamics In glaciology , an ice sheet , also known as a continental glacier , is a mass of glacial ice that covers surrounding terrain and is greater than 50,000 km (19,000 sq mi). The only current ice sheets are

4662-442: 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

4736-416: 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 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

4810-475: 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

4884-415: 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

4958-484: The predatory skua seabird. Scarce mention of the glacier tongue's surface, which is more than a mile wide, is made in popular literature. A notable exception is in Ernest Shackleton's book, South! The leader of a December 1916 search party seeking fellow explorers missing in vicinity of the glacier tongue made the following report to Shackleton: On January 2 thick weather caused party to lay up. On 3rd, glacier

5032-565: 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

5106-448: 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

5180-525: 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

5254-460: 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

5328-867: 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

5402-451: Was further examined, and several slopes formed by snow led to top of glacier, but crevasses between slope and the tongue prevented crossing. The party then proceeded round the Tongue to Tent Island, which was also searched, a complete tour of the island being made. The dynamics within floating ice streams such as the Erebus Glacier Tongue are complex. For instance, typically ice streams such as

5476-520: 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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