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Ice shelf

An ice shelf is a large platform of glacial ice floating on the ocean, fed by one or multiple tributary glaciers. Ice shelves form along coastlines where the ice thickness is insufficient to displace the more dense surrounding ocean water. The boundary between the ice shelf (floating) and grounded ice (resting on bedrock or sediment) is referred to as the grounding line; the boundary between the ice shelf and the open ocean (often covered by sea ice) is the ice front or calving front.

View of the Larsen Ice Shelf grounding line between Mamelon Point and Hodges Point along the Foyn Coast of the Antarctic Peninsula. The floating ice shelf is in the left foreground, and the grounding line is visible as an abrupt change in surface slope due to flexure caused by the buoyancy force where the ice reaches flotation.

Ice shelves are found in Antarctica and the Arctic (Greenland, Northern Canada, and the Russian Arctic), and can range in thickness from about 100–1,000 m (330–3,280 ft). The world's largest ice shelves are the Ross Ice Shelf and the Filchner-Ronne Ice Shelf in Antarctica.

The movement of ice shelves is principally driven by gravity-induced pressure from the grounded ice.[1] That flow continually moves ice from the grounding line to the seaward front of the shelf. Typically, a shelf front will extend forward for years or decades between major calving events (calving is the sudden release and breaking away of a mass of ice from a glacier, iceberg, ice front, ice shelf, or crevasse).[2][3] Snow accumulation on the upper surface and melting from the lower surface are also important to the mass balance of an ice shelf. Ice may also accrete onto the underside of the shelf.

The effects of climate change are visible in the changes to the cryosphere, such as reduction in sea ice and ice sheets, and disruption of ice shelves. In the last several decades, glaciologists have observed consistent decreases in ice shelf extent through melt, calving, and complete disintegration of some shelves.[4] Well studied examples include disruptions of the Thwaites Ice Shelf, Larsen Ice Shelf, Filchner–Ronne Ice Shelf (all three in the Antarctic) and the disruption of the Ellesmere Ice Shelf in the Arctic.

Definition edit

 
Some named Antarctic iceshelves.
 
Ice shelf extending approximately 6 miles into the Antarctic Sound from Joinville Island

An ice shelf is "a floating slab of ice originating from land of considerable thickness extending from the coast (usually of great horizontal extent with a very gently sloping surface), resulting from the flow of ice sheets, initially formed by the accumulation of snow, and often filling embayments in the coastline of an ice sheet."[5]: 2234 

In contrast, sea ice is formed on water, is much thinner (typically less than 3 m (9.8 ft)), and forms throughout the Arctic Ocean. It is also found in the Southern Ocean around the continent of Antarctica.

The term captured ice shelf has been used for the ice over a subglacial lake, such as Lake Vostok.

Properties edit

 
Panorama of Ross Ice Shelf

Ice shelves are thick plates of ice, formed continuously by glaciers, that float atop an ocean. The shelves act as "brakes" for the glaciers. These shelves serve another important purpose—"they moderate the amount of melting that occurs on the glaciers' surfaces. Once their ice shelves are removed, the glaciers increase in speed due to meltwater percolation and/or a reduction of braking forces, and they may begin to dump more ice into the ocean than they gather as snow in their catchments. Glacier ice speed increases are already observed in Peninsula areas where ice shelves disintegrated in prior years."[6]

Height edit

The density contrast between glacial ice and liquid water means that at least 1/9 of the floating ice is above the ocean surface, depending on how much pressurized air is contained in the bubbles within the glacial ice, stemming from compressed snow. The formula for the denominators above is  , density of cold seawater is about 1028 kg/m3 and that of glacial ice from about 850 kg/m3[7][8] to well below 920 kg/m3, the limit for very cold ice without bubbles.[9][10] The height of the shelf above the sea can be even larger, if there is much less dense firn and snow above the glacier ice.

By country or region edit

Antarctica edit

 
An image of Antarctica differentiating its landmass (dark grey), ice shelves (light grey), and sea ice (white)[11]

A large portion of the Antarctic coastline has ice shelves attached.[12] Their aggregate area is over 1,550,000 square kilometers (600,000 square miles).[13]

It has been found that of all the ice shelves on Earth, nearly all of them are in Antarctica.[14]: 2234 

In steady state, about half of Antarctica's ice shelf mass is lost to basal melt and half is lost to calving, but the relative importance of each process varies significantly between ice shelves.[15][16] In recent decades, Antarctica's ice shelves have been out of balance, as they have lost more mass to basal melt and calving than has been replenished by the influx of new ice and snow.[17]

Ross Ice Shelf edit

 
Ross Ice Shelf: "The mystic Barrier" at Bay of Whales. Note humans for size comparison (dark spots next to the large chunk of sea ice at left image border).

The Ross Ice Shelf is the largest ice shelf of Antarctica (as of 2013, an area of roughly 500,809 square kilometres (193,363 sq mi)[18] and about 800 kilometres (500 mi) across: about the size of France).[19] 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 (50 and 160 ft) high above the water surface.[20] Ninety percent of the floating ice, however, is below the water surface.

Most of Ross Ice Shelf is in the Ross Dependency claimed by New Zealand. It floats in, and covers, a large southern portion of the Ross Sea and the entire Roosevelt Island located in the east of the Ross Sea.

Filchner–Ronne Ice Shelf edit

The seaward side of the Filchner–Ronne ice shelf is divided into Eastern (Filchner) and the larger Western (Ronne) sections by Berkner Island. The whole ice shelf covers some 430,000 km2, making it the second largest ice shelf in Antarctica (and on Earth), after the Ross Ice Shelf. It grows perpetually due to a flow of inland ice sheets. From time to time, when the shearing stresses exceed the strength of the ice, cracks form and large parts of the ice sheet separate from the ice shelf and float off and disperse as icebergs. This is known as calving.

Arctic edit

Canada edit

All Canadian ice shelves are attached to Ellesmere Island and lie north of 82°N. Ice shelves that are still in existence are the Alfred Ernest Ice Shelf, Ward Hunt Ice Shelf, Milne Ice Shelf and Smith Ice Shelf. The M'Clintock Ice Shelf broke up from 1963 to 1966; the Ayles Ice Shelf broke up in 2005; and the Markham Ice Shelf broke up in 2008. The remaining ice shelves have also lost a significant amount of their area over time, with the Milne Ice Shelf being the last to be affected, with it breaking off in August 2020.

Russia edit

The Matusevich Ice Shelf was a 222 square kilometers (86 square miles) ice shelf located in Severnaya Zemlya being fed by some of the largest ice caps on October Revolution Island, the Karpinsky Ice Cap to the south and the Rusanov Ice Cap to the north.[21] In 2012 it ceased to exist.[22]

Impacts of climate change edit

The effects of climate change are visible in the changes to the cryosphere, such as reduction in sea ice and ice sheets, and disruption of ice shelves.

The melting of the Greenland and West Antarctic ice sheets will continue to contribute to sea level rise over long time-scales. The Greenland ice sheet loss is mainly driven by melt from the top. Antarctic ice loss is driven by warm ocean water melting the outlet glaciers.[23]: 1215 

Future melt of the West Antarctic ice sheet is potentially abrupt under a high emission scenario, as a consequence of a partial collapse.[24]: 595–596  Part of the ice sheet is grounded on bedrock below sea level. This makes it possibly vulnerable to the self-enhancing process of marine ice sheet instability. Marine ice cliff instability could also contribute to a partial collapse. But there is limited evidence for its importance.[23]: 1269–1270  A partial collapse of the ice sheet would lead to rapid sea level rise and a local decrease in ocean salinity. It would be irreversible for decades and possibly even millennia.[24]: 595–596  The complete loss of the West Antarctic ice sheet would cause over 5 metres (16 ft) of sea level rise.[25]

In contrast to the West Antarctic ice sheet, melt of the Greenland ice sheet is projected to take place more gradually over millennia.[24]: 595–596  Sustained warming between 1 °C (1.8 °F) (low confidence) and 4 °C (7.2 °F) (medium confidence) would lead to a complete loss of the ice sheet. This would contribute 7 m (23 ft) to sea levels globally.[26]: 363  The ice loss could become irreversible due to a further self-enhancing feedback. This is called the elevation-surface mass balance feedback. When ice melts on top of the ice sheet, the elevation drops. Air temperature is higher at lower altitudes, so this promotes further melting.[26]: 362 

Disruption edit

 
Processes around an Antarctic ice shelf
 
Glacier-ice shelf interactions

In the last several decades, glaciologists have observed consistent decreases in ice shelf extent through melt, calving, and complete disintegration of some shelves.[4] Well studied examples include disruptions of the Thwaites Ice Shelf, Larsen Ice Shelf, Filchner–Ronne Ice Shelf (all three in the Antarctic) and the disruption of the Ellesmere Ice Shelf in the Arctic.

Disruption of Thwaites Ice Shelf edit

 
Thwaites Ice Shelf (Antarctica)

Thwaites Ice Shelf (), is an Antarctic ice shelf in the Amundsen Sea. It was named by ACAN[27] 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.[28][29] Since the 1980s, the Thwaites glacier, nicknamed the "Doomsday glacier",[30] 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.[31] 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.[30][32]

According to the American Geophysical Union in a 2021 study, the Thwaites Eastern Ice Shelf (TEIS) buttresses one-third of Thwaites glacier. Removal of the shelf has the potential to increase the contribution of Thwaites glacier to sea level rise by up to 25%.[33] As of 2021, the ice shelf appears to be losing its grip on a submarine shoal that acts as a pinning point and the shear margin that separates the Thwaites Eastern Ice Shelf from the Thwaites glacier Tongue has extended, further weakening the ice shelf connection to the pinning point.[33]

A sequence of Sentinel-1 radar imagery shows that parallel wing and comb cracks have recently formed rifts at high angles to the main shear margin and are propagating into the central part of the ice shelf at rates as high as 2 km per year. Satellite data, ground-penetrating radar, and GPS measurements taken in 2021 indicate that collapse of the ice shelf may be initiated by intersection of rifts with hidden basal crevasse zones as soon as 2026.[33]

Complete melting of Thwaites glacier is predicted to increase global sea levels by 65 cm (2.13 ft) according to the European Geosciences Union,[34] and the Cooperative Institute for Research in Environmental Sciences states that the collapse of Thwaites glacier could ultimately lead to sea-level rise of up to 3 meters[35] if it draws the Pine Island and surrounding glaciers with it, due to marine ice sheet instability. However, both of these processes would take time: a Science Magazine interview with the International Thwaites Glacier Collaboration researchers who had discovered the impending collapse of the ice shelf noted that the glacier itself would still take approximately several centuries to collapse even without the ice shelf,[36] and a 2022 assessment of tipping points in the climate system stated that while the West Antarctic Ice Sheet may be committed to disintegration at between 1°C and 3°C, the timescale for its collapse after that ranges between 500 and 13,000 years, with the most likely estimate of 2000 years.[37][38]

Disruption of Larsen Ice Shelf edit

Two sections of Antarctica's Larsen Ice Shelf broke apart into hundreds of unusually small fragments (hundreds of meters wide or less) in 1995 and 2002, Larsen C calved a huge ice island in 2017.[39]

 
An image of the collapsing Larsen B Ice Shelf and a comparison of this to the U.S. state of Rhode Island.
The Larsen disintegration events were unusual by past standards. Typically, ice shelves lose mass by iceberg calving and by melting at their upper and lower surfaces. The disintegration events were linked by The Independent newspaper in 2005 to ongoing climate warming in the Antarctic Peninsula, about 0.5˚C (0.9˚F) per decade since the late 1940s.[40] According to a paper published in Journal of Climate in 2006, the peninsula at Faraday station warmed by 2.94˚C (5.3˚F) from 1951 to 2004, much faster than Antarctica as a whole and faster than the global trend; anthropogenic global warming causes this localized warming through a strengthening of the winds circling the Antarctic.[41]

Disruption of Larsen B Ice Shelf edit

 
The collapse of Larsen B, showing the diminishing extent of the shelf from 1998 to 2002.

From 31 January 2002 to March 2002 the Larsen B sector partially collapsed and parts broke up, 3,250 km2 (1,250 sq mi) of ice 220 m (720 ft) thick, an area comparable to the US state of Rhode Island.[42] In 2015, a study concluded that the remaining Larsen B ice-shelf would disintegrate by 2020, based on observations of faster flow and rapid thinning of glaciers in the area.[43]

Larsen B was stable for at least 10,000 years, essentially the entire Holocene period since the last glacial period.[44] By contrast, Larsen A was absent for a significant part of that period, reforming about 4,000 years ago.

Despite its great age, the Larsen B was clearly in trouble at the time of the collapse. With warm currents eating away the underside of the shelf, it had become a "hotspot of global warming".[45] It broke over a period of three weeks or less, with a factor in this fast break-up being the powerful effects of water; ponds of meltwater formed on the surface during the near 24 hours of daylight in the summertime, flowed down into cracks and, acting like a multitude of wedges, levered the shelf apart.[46][47] Other likely factors in the break-up were the higher ocean temperatures and the decline of the ice of the peninsula.[48]

In the austral winter of 2011, a large expanse of sea ice formed over the embayment that was once covered by the land-fast shelf of fresh-water glacial ice of Larsen B. This enormous ice pack persisted through January 2022 when it suddenly broke-up over the course of a few days, "taking with it a Philadelphia-sized piece of the Scar Inlet Ice Shelf," according to NASA scientists examining images from the Terra and Aqua satellites.[49]

Disruption of Filchner–Ronne Ice Shelf edit

In October 1998, the iceberg A-38 broke off the Filchner–Ronne ice shelf. It had an extent of roughly 150 by 50 km and was thus larger than Delaware. It later broke up again into three parts. A similar-sized calving in May 2000 created an iceberg 167 by 32 km in extent, dubbed A-43 – the disintegration of this is thought to have been responsible for the November 2006 sighting of several large icebergs from the coast of the South Island of New Zealand, the first time since 1931 that any icebergs had been observed from the New Zealand mainland. A large group of small icebergs (the largest some 1000 metres in length), were seen off the south-east coast of the island, with one of them drifting close enough to shore to be visible from the hills above the city of Dunedin. If these were indeed the remnants of this calving, then over the course of five and a half years they had travelled slowly north and also east around over half the globe, a journey of some 13,500 km.[50]

From January 12 and January 13, 2010, an area of sea ice larger than the state of Rhode Island, or one-seventh the size of Wales, broke away from the Ronne–Filchner Ice Shelf and shattered into many smaller pieces. The Moderate-Resolution Imaging Spectroradiometer (MODIS) on NASA's Aqua and Terra satellites captured this event in this series of photo-like images.[51]

In May 2021, Iceberg A-76 broke off the northwest corner of the shelf. At 4320 km2,[52] it is larger than Majorca, several times larger than Iceberg A-74 which calved in the same year, or approximately 14% the size of Belgium.

The ice of the Filchner–Ronne ice shelf can be as thick as 600 m; the water below is about 1400 m deep at the deepest point.

The international Filchner–Ronne Ice Shelf Programme (FRISP) was initiated in 1973 to study the ice shelf.[53]

A study published in Nature in 2012 by scientists from the Alfred Wegener Institute for Polar and Marine Research in Germany, and funded by the Ice2Sea initiative, predicts the disappearance of the 450,000 km2 (170,000 sq mi) vast ice shelf in Antarctica by the end of the century which could – indirectly – add up to 4.4 mm (0.17 in) of rise of sea level each year.[54]

Disruption of Ellesmere Ice Shelf (Arctic) edit

The Ellesmere ice shelf was reduced by 90% in the twentieth century, leaving the separate Alfred Ernest, Ayles, Milne, Ward Hunt, and Markham ice shelves. A 1986 survey of Canadian ice shelves found that 48 km2 (3.3 cubic kilometres) of ice calved from the Milne and Ayles ice shelves between 1959 and 1974.[55] The Ayles Ice Shelf calved entirely on August 13, 2005. The Ward Hunt Ice Shelf, the largest remaining section of thick (>10 meters (33 feet)) landfast sea ice along the northern coastline of Ellesmere Island, lost 600 square kilometers (230 square miles) of ice in a massive calving in 1961–1962.[56] It further decreased by 27% in thickness (13 meters (43 feet)) between 1967 and 1999.[57] In the summer of 2002, the Ward Ice Shelf experienced another major breakup,[58] and other instances of note happened in 2008 and 2010 as well.[59] The last remnant to remain mostly intact, the Milne Ice Shelf, also ultimately experienced a major breakup at the end of July 2020, losing over 40% of its area.[60]

The Ellesmere Ice Shelf was the largest ice shelf in the Arctic, encompassing about 9,100 square kilometres (3,500 square miles) of the north coast of Ellesmere Island, Nunavut, Canada.[61] The ice shelf was first documented by the British Arctic Expedition of 1875–76, in which Lieutenant Pelham Aldrich's party went from Cape Sheridan to Cape Alert.[62] The continuous mass of the Ellesmere Ice Shelf had been in place for at least 3,000 years.[61]

During the twentieth century, the Ellesmere Ice Shelf broke up into six separate shelves. From west to east, these were the Serson Ice Shelf, Petersen Ice Shelf, Milne Ice Shelf, Ayles Ice Shelf, Ward Hunt Ice Shelf, and Markham Ice Shelf.[63] The smaller pieces continued to disintegrate.

In April 2000, satellite images revealed that a large crack in the Ward Hunt shelf had begun to form, and in 2003 it was announced that the ice sheet had split completely in two in 2002, releasing a huge pool of freshwater from the largest epishelf lake in the Northern Hemisphere, located in Disraeli Fjord.[64] In April 2008, scientists discovered that the shelf fractured into dozens of deep, multi-faceted cracks.[65]

On August 13, 2005, The Ayles Ice Shelf, which was located approximately 800 km (500 mi) south of the North Pole, broke away from the coast forming the giant Ayles Ice Island 37 metres (121 ft) thick and measuring around 14 by 5 km (8.7 by 3.1 mi) in size with an area of approximately 66 km2 (25 sq mi) or 2.6 km3 (0.62 cu mi) in volume.[61]

The Milne Ice Shelf was the second largest segment of the former Ellesmere Ice Shelf. It suffered a 40% disintegration in July 2020 with the loss of a research camp, including instruments for measuring water flow.[66]

See also edit

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External links edit

shelf, confused, with, shelf, shelf, large, platform, glacial, floating, ocean, multiple, tributary, glaciers, shelves, form, along, coastlines, where, thickness, insufficient, displace, more, dense, surrounding, ocean, water, boundary, between, shelf, floatin. Not to be confused with Shelf ice or Sea ice An ice shelf is a large platform of glacial ice floating on the ocean fed by one or multiple tributary glaciers Ice shelves form along coastlines where the ice thickness is insufficient to displace the more dense surrounding ocean water The boundary between the ice shelf floating and grounded ice resting on bedrock or sediment is referred to as the grounding line the boundary between the ice shelf and the open ocean often covered by sea ice is the ice front or calving front View of the Larsen Ice Shelf grounding line between Mamelon Point and Hodges Point along the Foyn Coast of the Antarctic Peninsula The floating ice shelf is in the left foreground and the grounding line is visible as an abrupt change in surface slope due to flexure caused by the buoyancy force where the ice reaches flotation Ice shelves are found in Antarctica and the Arctic Greenland Northern Canada and the Russian Arctic and can range in thickness from about 100 1 000 m 330 3 280 ft The world s largest ice shelves are the Ross Ice Shelf and the Filchner Ronne Ice Shelf in Antarctica The movement of ice shelves is principally driven by gravity induced pressure from the grounded ice 1 That flow continually moves ice from the grounding line to the seaward front of the shelf Typically a shelf front will extend forward for years or decades between major calving events calving is the sudden release and breaking away of a mass of ice from a glacier iceberg ice front ice shelf or crevasse 2 3 Snow accumulation on the upper surface and melting from the lower surface are also important to the mass balance of an ice shelf Ice may also accrete onto the underside of the shelf The effects of climate change are visible in the changes to the cryosphere such as reduction in sea ice and ice sheets and disruption of ice shelves In the last several decades glaciologists have observed consistent decreases in ice shelf extent through melt calving and complete disintegration of some shelves 4 Well studied examples include disruptions of the Thwaites Ice Shelf Larsen Ice Shelf Filchner Ronne Ice Shelf all three in the Antarctic and the disruption of the Ellesmere Ice Shelf in the Arctic Contents 1 Definition 2 Properties 2 1 Height 3 By country or region 3 1 Antarctica 3 1 1 Ross Ice Shelf 3 1 2 Filchner Ronne Ice Shelf 3 2 Arctic 3 2 1 Canada 3 2 2 Russia 4 Impacts of climate change 5 Disruption 5 1 Disruption of Thwaites Ice Shelf 5 2 Disruption of Larsen Ice Shelf 5 2 1 Disruption of Larsen B Ice Shelf 5 3 Disruption of Filchner Ronne Ice Shelf 5 4 Disruption of Ellesmere Ice Shelf Arctic 6 See also 7 References 8 External linksDefinition edit nbsp Some named Antarctic iceshelves nbsp Ice shelf extending approximately 6 miles into the Antarctic Sound from Joinville Island An ice shelf is a floating slab of ice originating from land of considerable thickness extending from the coast usually of great horizontal extent with a very gently sloping surface resulting from the flow of ice sheets initially formed by the accumulation of snow and often filling embayments in the coastline of an ice sheet 5 2234 In contrast sea ice is formed on water is much thinner typically less than 3 m 9 8 ft and forms throughout the Arctic Ocean It is also found in the Southern Ocean around the continent of Antarctica The term captured ice shelf has been used for the ice over a subglacial lake such as Lake Vostok Properties edit nbsp Panorama of Ross Ice Shelf Ice shelves are thick plates of ice formed continuously by glaciers that float atop an ocean The shelves act as brakes for the glaciers These shelves serve another important purpose they moderate the amount of melting that occurs on the glaciers surfaces Once their ice shelves are removed the glaciers increase in speed due to meltwater percolation and or a reduction of braking forces and they may begin to dump more ice into the ocean than they gather as snow in their catchments Glacier ice speed increases are already observed in Peninsula areas where ice shelves disintegrated in prior years 6 Height edit The density contrast between glacial ice and liquid water means that at least 1 9 of the floating ice is above the ocean surface depending on how much pressurized air is contained in the bubbles within the glacial ice stemming from compressed snow The formula for the denominators above is 1 r seawater r glacial ice r seawater textstyle 1 rho text seawater rho text glacial ice rho text seawater nbsp density of cold seawater is about 1028 kg m3 and that of glacial ice from about 850 kg m3 7 8 to well below 920 kg m3 the limit for very cold ice without bubbles 9 10 The height of the shelf above the sea can be even larger if there is much less dense firn and snow above the glacier ice By country or region editAntarctica edit See also List of Antarctic ice shelves nbsp An image of Antarctica differentiating its landmass dark grey ice shelves light grey and sea ice white 11 A large portion of the Antarctic coastline has ice shelves attached 12 Their aggregate area is over 1 550 000 square kilometers 600 000 square miles 13 It has been found that of all the ice shelves on Earth nearly all of them are in Antarctica 14 2234 In steady state about half of Antarctica s ice shelf mass is lost to basal melt and half is lost to calving but the relative importance of each process varies significantly between ice shelves 15 16 In recent decades Antarctica s ice shelves have been out of balance as they have lost more mass to basal melt and calving than has been replenished by the influx of new ice and snow 17 Ross Ice Shelf edit nbsp Ross Ice Shelf The mystic Barrier at Bay of Whales Note humans for size comparison dark spots next to the large chunk of sea ice at left image border This section is an excerpt from Ross Ice Shelf edit The Ross Ice Shelf is the largest ice shelf of Antarctica as of 2013 update an area of roughly 500 809 square kilometres 193 363 sq mi 18 and about 800 kilometres 500 mi across about the size of France 19 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 50 and 160 ft high above the water surface 20 Ninety percent of the floating ice however is below the water surface Most of Ross Ice Shelf is in the Ross Dependency claimed by New Zealand It floats in and covers a large southern portion of the Ross Sea and the entire Roosevelt Island located in the east of the Ross Sea Filchner Ronne Ice Shelf edit This section is an excerpt from Filchner Ronne Ice Shelf Description edit The seaward side of the Filchner Ronne ice shelf is divided into Eastern Filchner and the larger Western Ronne sections by Berkner Island The whole ice shelf covers some 430 000 km2 making it the second largest ice shelf in Antarctica and on Earth after the Ross Ice Shelf It grows perpetually due to a flow of inland ice sheets From time to time when the shearing stresses exceed the strength of the ice cracks form and large parts of the ice sheet separate from the ice shelf and float off and disperse as icebergs This is known as calving Arctic edit Canada edit All Canadian ice shelves are attached to Ellesmere Island and lie north of 82 N Ice shelves that are still in existence are the Alfred Ernest Ice Shelf Ward Hunt Ice Shelf Milne Ice Shelf and Smith Ice Shelf The M Clintock Ice Shelf broke up from 1963 to 1966 the Ayles Ice Shelf broke up in 2005 and the Markham Ice Shelf broke up in 2008 The remaining ice shelves have also lost a significant amount of their area over time with the Milne Ice Shelf being the last to be affected with it breaking off in August 2020 Russia edit The Matusevich Ice Shelf was a 222 square kilometers 86 square miles ice shelf located in Severnaya Zemlya being fed by some of the largest ice caps on October Revolution Island the Karpinsky Ice Cap to the south and the Rusanov Ice Cap to the north 21 In 2012 it ceased to exist 22 Impacts of climate change editThe effects of climate change are visible in the changes to the cryosphere such as reduction in sea ice and ice sheets and disruption of ice shelves This section is an excerpt from Effects of climate change Ice sheets decline edit The melting of the Greenland and West Antarctic ice sheets will continue to contribute to sea level rise over long time scales The Greenland ice sheet loss is mainly driven by melt from the top Antarctic ice loss is driven by warm ocean water melting the outlet glaciers 23 1215 Future melt of the West Antarctic ice sheet is potentially abrupt under a high emission scenario as a consequence of a partial collapse 24 595 596 Part of the ice sheet is grounded on bedrock below sea level This makes it possibly vulnerable to the self enhancing process of marine ice sheet instability Marine ice cliff instability could also contribute to a partial collapse But there is limited evidence for its importance 23 1269 1270 A partial collapse of the ice sheet would lead to rapid sea level rise and a local decrease in ocean salinity It would be irreversible for decades and possibly even millennia 24 595 596 The complete loss of the West Antarctic ice sheet would cause over 5 metres 16 ft of sea level rise 25 In contrast to the West Antarctic ice sheet melt of the Greenland ice sheet is projected to take place more gradually over millennia 24 595 596 Sustained warming between 1 C 1 8 F low confidence and 4 C 7 2 F medium confidence would lead to a complete loss of the ice sheet This would contribute 7 m 23 ft to sea levels globally 26 363 The ice loss could become irreversible due to a further self enhancing feedback This is called the elevation surface mass balance feedback When ice melts on top of the ice sheet the elevation drops Air temperature is higher at lower altitudes so this promotes further melting 26 362 Disruption editSee also Sea level rise nbsp Processes around an Antarctic ice shelf nbsp Glacier ice shelf interactions In the last several decades glaciologists have observed consistent decreases in ice shelf extent through melt calving and complete disintegration of some shelves 4 Well studied examples include disruptions of the Thwaites Ice Shelf Larsen Ice Shelf Filchner Ronne Ice Shelf all three in the Antarctic and the disruption of the Ellesmere Ice Shelf in the Arctic Disruption of Thwaites Ice Shelf edit nbsp Thwaites Ice Shelf Antarctica This section is an excerpt from Thwaites Ice Shelf edit Thwaites Ice Shelf is an Antarctic ice shelf in the Amundsen Sea It was named by ACAN 27 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 28 29 Since the 1980s the Thwaites glacier nicknamed the Doomsday glacier 30 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 31 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 30 32 According to the American Geophysical Union in a 2021 study the Thwaites Eastern Ice Shelf TEIS buttresses one third of Thwaites glacier Removal of the shelf has the potential to increase the contribution of Thwaites glacier to sea level rise by up to 25 33 As of 2021 update the ice shelf appears to be losing its grip on a submarine shoal that acts as a pinning point and the shear margin that separates the Thwaites Eastern Ice Shelf from the Thwaites glacier Tongue has extended further weakening the ice shelf connection to the pinning point 33 A sequence of Sentinel 1 radar imagery shows that parallel wing and comb cracks have recently formed rifts at high angles to the main shear margin and are propagating into the central part of the ice shelf at rates as high as 2 km per year Satellite data ground penetrating radar and GPS measurements taken in 2021 indicate that collapse of the ice shelf may be initiated by intersection of rifts with hidden basal crevasse zones as soon as 2026 33 Complete melting of Thwaites glacier is predicted to increase global sea levels by 65 cm 2 13 ft according to the European Geosciences Union 34 and the Cooperative Institute for Research in Environmental Sciences states that the collapse of Thwaites glacier could ultimately lead to sea level rise of up to 3 meters 35 if it draws the Pine Island and surrounding glaciers with it due to marine ice sheet instability However both of these processes would take time a Science Magazine interview with the International Thwaites Glacier Collaboration researchers who had discovered the impending collapse of the ice shelf noted that the glacier itself would still take approximately several centuries to collapse even without the ice shelf 36 and a 2022 assessment of tipping points in the climate system stated that while the West Antarctic Ice Sheet may be committed to disintegration at between 1 C and 3 C the timescale for its collapse after that ranges between 500 and 13 000 years with the most likely estimate of 2000 years 37 38 Disruption of Larsen Ice Shelf editTwo sections of Antarctica s Larsen Ice Shelf broke apart into hundreds of unusually small fragments hundreds of meters wide or less in 1995 and 2002 Larsen C calved a huge ice island in 2017 39 This section is an excerpt from Larsen Ice Shelf Breakup edit nbsp An image of the collapsing Larsen B Ice Shelf and a comparison of this to the U S state of Rhode Island The Larsen disintegration events were unusual by past standards Typically ice shelves lose mass by iceberg calving and by melting at their upper and lower surfaces The disintegration events were linked by The Independent newspaper in 2005 to ongoing climate warming in the Antarctic Peninsula about 0 5 C 0 9 F per decade since the late 1940s 40 According to a paper published in Journal of Climate in 2006 the peninsula at Faraday station warmed by 2 94 C 5 3 F from 1951 to 2004 much faster than Antarctica as a whole and faster than the global trend anthropogenic global warming causes this localized warming through a strengthening of the winds circling the Antarctic 41 Disruption of Larsen B Ice Shelf edit This section is an excerpt from Larsen Ice Shelf Larsen B edit nbsp The collapse of Larsen B showing the diminishing extent of the shelf from 1998 to 2002 From 31 January 2002 to March 2002 the Larsen B sector partially collapsed and parts broke up 3 250 km2 1 250 sq mi of ice 220 m 720 ft thick an area comparable to the US state of Rhode Island 42 In 2015 a study concluded that the remaining Larsen B ice shelf would disintegrate by 2020 based on observations of faster flow and rapid thinning of glaciers in the area 43 Larsen B was stable for at least 10 000 years essentially the entire Holocene period since the last glacial period 44 By contrast Larsen A was absent for a significant part of that period reforming about 4 000 years ago Despite its great age the Larsen B was clearly in trouble at the time of the collapse With warm currents eating away the underside of the shelf it had become a hotspot of global warming 45 It broke over a period of three weeks or less with a factor in this fast break up being the powerful effects of water ponds of meltwater formed on the surface during the near 24 hours of daylight in the summertime flowed down into cracks and acting like a multitude of wedges levered the shelf apart 46 47 Other likely factors in the break up were the higher ocean temperatures and the decline of the ice of the peninsula 48 In the austral winter of 2011 a large expanse of sea ice formed over the embayment that was once covered by the land fast shelf of fresh water glacial ice of Larsen B This enormous ice pack persisted through January 2022 when it suddenly broke up over the course of a few days taking with it a Philadelphia sized piece of the Scar Inlet Ice Shelf according to NASA scientists examining images from the Terra and Aqua satellites 49 Disruption of Filchner Ronne Ice Shelf edit This section is an excerpt from Filchner Ronne Ice Shelf Disintegration calving edit In October 1998 the iceberg A 38 broke off the Filchner Ronne ice shelf It had an extent of roughly 150 by 50 km and was thus larger than Delaware It later broke up again into three parts A similar sized calving in May 2000 created an iceberg 167 by 32 km in extent dubbed A 43 the disintegration of this is thought to have been responsible for the November 2006 sighting of several large icebergs from the coast of the South Island of New Zealand the first time since 1931 that any icebergs had been observed from the New Zealand mainland A large group of small icebergs the largest some 1000 metres in length were seen off the south east coast of the island with one of them drifting close enough to shore to be visible from the hills above the city of Dunedin If these were indeed the remnants of this calving then over the course of five and a half years they had travelled slowly north and also east around over half the globe a journey of some 13 500 km 50 From January 12 and January 13 2010 an area of sea ice larger than the state of Rhode Island or one seventh the size of Wales broke away from the Ronne Filchner Ice Shelf and shattered into many smaller pieces The Moderate Resolution Imaging Spectroradiometer MODIS on NASA s Aqua and Terra satellites captured this event in this series of photo like images 51 In May 2021 Iceberg A 76 broke off the northwest corner of the shelf At 4320 km2 52 it is larger than Majorca several times larger than Iceberg A 74 which calved in the same year or approximately 14 the size of Belgium The ice of the Filchner Ronne ice shelf can be as thick as 600 m the water below is about 1400 m deep at the deepest point The international Filchner Ronne Ice Shelf Programme FRISP was initiated in 1973 to study the ice shelf 53 A study published in Nature in 2012 by scientists from the Alfred Wegener Institute for Polar and Marine Research in Germany and funded by the Ice2Sea initiative predicts the disappearance of the 450 000 km2 170 000 sq mi vast ice shelf in Antarctica by the end of the century which could indirectly add up to 4 4 mm 0 17 in of rise of sea level each year 54 Disruption of Ellesmere Ice Shelf Arctic editThe Ellesmere ice shelf was reduced by 90 in the twentieth century leaving the separate Alfred Ernest Ayles Milne Ward Hunt and Markham ice shelves A 1986 survey of Canadian ice shelves found that 48 km2 3 3 cubic kilometres of ice calved from the Milne and Ayles ice shelves between 1959 and 1974 55 The Ayles Ice Shelf calved entirely on August 13 2005 The Ward Hunt Ice Shelf the largest remaining section of thick gt 10 meters 33 feet landfast sea ice along the northern coastline of Ellesmere Island lost 600 square kilometers 230 square miles of ice in a massive calving in 1961 1962 56 It further decreased by 27 in thickness 13 meters 43 feet between 1967 and 1999 57 In the summer of 2002 the Ward Ice Shelf experienced another major breakup 58 and other instances of note happened in 2008 and 2010 as well 59 The last remnant to remain mostly intact the Milne Ice Shelf also ultimately experienced a major breakup at the end of July 2020 losing over 40 of its area 60 This section is an excerpt from Ellesmere Ice Shelf edit The Ellesmere Ice Shelf was the largest ice shelf in the Arctic encompassing about 9 100 square kilometres 3 500 square miles of the north coast of Ellesmere Island Nunavut Canada 61 The ice shelf was first documented by the British Arctic Expedition of 1875 76 in which Lieutenant Pelham Aldrich s party went from Cape Sheridan to Cape Alert 62 The continuous mass of the Ellesmere Ice Shelf had been in place for at least 3 000 years 61 During the twentieth century the Ellesmere Ice Shelf broke up into six separate shelves From west to east these were the Serson Ice Shelf Petersen Ice Shelf Milne Ice Shelf Ayles Ice Shelf Ward Hunt Ice Shelf and Markham Ice Shelf 63 The smaller pieces continued to disintegrate In April 2000 satellite images revealed that a large crack in the Ward Hunt shelf had begun to form and in 2003 it was announced that the ice sheet had split completely in two in 2002 releasing a huge pool of freshwater from the largest epishelf lake in the Northern Hemisphere located in Disraeli Fjord 64 In April 2008 scientists discovered that the shelf fractured into dozens of deep multi faceted cracks 65 On August 13 2005 The Ayles Ice Shelf which was located approximately 800 km 500 mi south of the North Pole broke away from the coast forming the giant Ayles Ice Island 37 metres 121 ft thick and measuring around 14 by 5 km 8 7 by 3 1 mi in size with an area of approximately 66 km2 25 sq mi or 2 6 km3 0 62 cu mi in volume 61 The Milne Ice Shelf was the second largest segment of the former Ellesmere Ice Shelf It suffered a 40 disintegration in July 2020 with the loss of a research camp including instruments for measuring water flow 66 See also editAntarctic sea ice Arctic sea ice decline Ice sheet dynamics List of Antarctic ice shelvesReferences edit Greve R Blatter H 2009 Dynamics of Ice Sheets and Glaciers Springer doi 10 1007 978 3 642 03415 2 ISBN 978 3 642 03414 5 Glossary of Glacier Terms Ellin Beltz 2006 Retrieved July 2009 Essentials of Geology 3rd edition Stephen Marshak a b Antarctic ice shelf hanging by thread European scientists July 10 2008 Yahoo News IPCC 2021 Annex VII Glossary Matthews J B R V Moller R van Diemen J S Fuglestvedt V Masson Delmotte C Mendez S Semenov A Reisinger eds In Climate Change 2021 The Physical Science Basis Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change Masson Delmotte V P Zhai A Pirani S L Connors C Pean S Berger N Caud Y Chen L Goldfarb M I Gomis M Huang K Leitzell E Lonnoy J B R Matthews T K Maycock T Waterfield O Yelekci R Yu and B Zhou eds Cambridge University Press Cambridge United Kingdom and New York NY USA pp 2215 2256 doi 10 1017 9781009157896 022 Larsen B Ice Shelf Collapses in Antarctica National Snow and Ice Data Center nsidc org Archived from the original on 14 July 2017 Retrieved 20 April 2019 Pidwirny Michael 2006 Glacial Processes www physicalgeography net Retrieved 2018 01 21 Shumskiy P A 1960 Density of Glacier Ice Journal of Glaciology 3 27 568 573 Bibcode 1960JGlac 3 568S doi 10 3189 S0022143000023686 ISSN 0022 1430 Densification www iceandclimate nbi ku dk 2009 09 11 Archived from the original on 2018 01 22 Retrieved 2018 01 21 Ice Thermal Properties www engineeringtoolbox com Retrieved 2018 01 21 Opposite Behaviors Arctic Sea Ice Shrinks Antarctic Grows www nasa gov 2012 10 23 Retrieved 2023 01 24 Bindschadler R Choi H Wichlacz A Bingham R Bohlander J Brunt K Corr H Drews R Fricker H 2011 07 18 Getting around 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Astrom Jan A Crawford Anna Cornford Stephen L Bevan Suzanne L Gladstone Rupert Zwinger Thomas Alley Karen Pettit Erin Bassis Jeremy Rapid fragmentation of Thwaites Eastern Ice Shelf West Antarctica Copernicus org Retrieved 2022 01 25 Kim Jin Woo Kim Duk jin Kim Seung Hee Ha Ho Kyung Lee Sang Hoon 2015 Disintegration and acceleration of Thwaites Ice Shelf on the Amundsen Sea revealed from remote sensing measurements GIScience amp Remote Sensing 52 4 498 509 doi 10 1080 15481603 2015 1041766 a b Cohen Li 2021 12 14 Doomsday glacier s last remaining ice shelf could collapse within 5 years and scientists warn it could rapidly raise sea levels CBS News Tinto K Bell R 2011 Progressive unpinning of Thwaites glacier from newly identified offshore ridge Constraints from aerogravity Geophysical Research Letters doi 10 1029 2011GL049026 Thwaites Antarctic glacier heading for dramatic change BBC News 2021 12 13 Retrieved 2021 12 18 a b c Pettit Erin C Wild Christian Alley Karen Muto Atsuhiro Truffer Martin Bevan Suzanne Louise Bassis Jeremy N Crawford Anna Scambos Ted A Benn Doug 2021 12 15 Collapse of Thwaites Eastern Ice Shelf by intersecting fractures AGU Fall Meeting New Orleans American Geophysical Union C34A 07 Douglas Benn I Luck Adrian Astrom Jan A Crawford Anna Cornford Stephen L Bevan Suzanne L Gladstone Rupert Zwinger Thomas Alley Karen Pettit Erin Bassis Jeremy Rapid fragmentation of Thwaites Eastern Ice Shelf West Antarctica Copernicus org Retrieved 2022 01 25 Cooperative Institute for Research in Environmental Sciences at the University of Colorado Boulder The Threat from Thwaites The Retreat of Antarctica s Riskiest Glacier Voosen Paul 13 December 2021 Ice shelf holding back keystone Antarctic glacier within years of failure Science Magazine Retrieved 2022 10 22 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 Armstrong McKay David Abrams Jesse Winkelmann Ricarda Sakschewski Boris Loriani Sina Fetzer Ingo Cornell Sarah Rockstrom Johan Staal Arie Lenton Timothy 9 September 2022 Exceeding 1 5 C global warming could trigger multiple climate tipping points Science 377 6611 doi 10 1126 science abn7950 hdl 10871 131584 ISSN 0036 8075 Armstrong McKay David 9 September 2022 Exceeding 1 5 C global warming could trigger multiple climate tipping points paper explainer climatetippingpoints info Retrieved 2 October 2022 Kropshofer Katharina 2017 10 09 Scientists hope damage to Larsen C ice shelf will reveal ecosystems The Guardian ISSN 0261 3077 Retrieved 2018 01 05 Connor Steve 2005 Ice shelf collapse was biggest for 10 000 years since Ice Age The Independent London 4 August online Marshall Gareth J Orr Andrew Van Lipzig Nicole P M King John C 2006 The Impact of a Changing Southern Hemisphere Annular Mode on Antarctic Peninsula Summer Temperatures PDF Journal of Climate 19 20 5388 5404 Bibcode 2006JCli 19 5388M doi 10 1175 JCLI3844 1 Hulbe Christina 2002 Larsen Ice Shelf 2002 warmest summer on record leads to disintegration Portland State University NASA Study Shows Antarctica s Larsen B Ice Shelf Nearing Its Final Act Press release NASA 14 May 2015 Ice Shelf disintegration threatens environment Queen s study Press release Kingston Ontario Queens University 3 August 2005 via American Association for the Advancement of Science s Eurekalert Pearce Fred 2006 The Last Generation How Nature Will Take Her Revenge for Climate Change Eden Project Books p 92 ISBN 978 1 903919 87 3 Larsen B Ice Shelf Collapses in Antarctica National Snow and Ice Data Center 18 March 2002 Archived from the original on 14 July 2017 Retrieved 2017 07 12 Antarctic Ice Shelf Collapse Triggered By Warmer Summers Office of News Services University of Colorado at Boulder 16 January 2001 Retrieved 2017 07 12 Experts challenge ice shelf claim Two scientists have claimed that climate change was not the only cause of the collapse of a 500bn tonne ice shelf in Antarctica six years ago BBC News 7 February 2008 Retrieved 21 October 2016 Hansen Kathryn Stevens Joshua January 26 2022 Larsen B Embayment Breaks Up NASA Earth Observatory National Aeronautics and Space Administration Retrieved February 6 2022 NIWA report National Institute of Water and Atmospheric Research Rapid Sea Ice Breakup along the Ronne Filchner Ice Shelf Meet the world s largest iceberg The ESA European Space Agency Retrieved 19 May 2021 6 2 1 Filchner Ronne Ice Shelf Programme Archived 2010 06 01 at the Wayback Machine WAIS The West Antarctic Ice Sheet Initiative New Antarctic Ice Shelf Threatened by Warming Reuters Scientific American 9 May 2012 Retrieved 5 Jan 2017 Jeffries Martin O Ice Island Calvings and Ice Shelf Changes Milne Ice Shelf and Ayles Ice Shelf Ellesmere Island N W T Archived 2019 09 28 at the Wayback Machine Arctic 39 1 March 1986 Hattersley Smith G The Ward Hunt Ice Shelf recent changes of the ice front Journal of Glaciology 4 415 424 1963 Vincent W F J A E Gibson M O Jeffries Ice shelf collapse climate change and habitat loss in the Canadian high Arctic Polar Record 37 201 133 142 2001 NASA Earth Observatory 2004 01 20 Breakup of the Ward Hunt Ice Shelf Canada Environment and Climate Change 2010 12 17 Ward Hunt ice shelf calving Canada ca www canada ca Retrieved 2018 01 05 Canada s last fully intact Arctic ice shelf collapses Reuters 2020 08 06 Retrieved 2020 08 07 a b c Ljunggren David July 29 2008 Giant chunks break off Canadian ice shelf Reuters Archived from the original on February 10 2015 Retrieved July 29 2008 Mueller initially estimated that 1 5 square miles of ice had broken off the shelf but increased that figure to eight square miles after studying the data more closely Whatever has kept this ice shelf in balance for 3 000 years is no longer keeping it in balance he told Reuters saying he too would not be surprised to see more ice breaking away from the Ward Hunt shelf this year Jeffries Martin O March 1986 Ice Island Calvings and Ice Shelf Changes Milne Ice Shelf and Ayles Ice Shelf Ellesmere Island N W T PDF Arctic 39 1 doi 10 14430 arctic2039 Archived from the original PDF on September 28 2019 Retrieved May 24 2008 Paulson Hannah August 7 2020 Collapsed Arctic ice shelf adds exclamation point to dire climate trends say scientists CBC Retrieved 26 October 2022 NASA Earth Observatory January 20 2004 Breakup of the Ward Hunt Ice Shelf Weber Bob April 12 2008 Cracks in Arctic ice shelf signal its demise The Star Toronto The Canadian Press Retrieved May 1 2010 Canada s last fully intact Arctic ice shelf collapses Reuters August 6 2020 Retrieved August 7 2020 External links edit nbsp Wikimedia Commons has media related to Ice shelf Further information from the Australian Antarctic Division Archived 2017 08 21 at the Wayback Machine http nsidc org quickfacts iceshelves html Archived 2010 06 15 at the Wayback Machine from the U S National Snow and Ice Data Center Retrieved from https en wikipedia org w index php title Ice shelf amp oldid 1216735838, wikipedia, wiki, book, books, library,

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