On 5 April 2009 the thin bridge of ice to Charcot Island splintered, and scientists expect it could cause the collapse of the Shelf. There are reports the shelf has exploded into hundreds of small icebergs. David Vaughan of the British Antarctic Survey has attributed these events to global warming.[1]
Wilkins Ice Shelf
2008 partial collapseDiagram showing region of ice preventing further collapse
The Wilkins Ice Shelf is a rectangular ice shelf about 80 nautical miles (150km) long and 60 nautical miles (110km) wide (150 by 110km (93 by 68mi)). This feature occupies the central part of Wilkins Sound, from which it takes its name. The name was proposed by the UK Antarctic Place-Names Committee (UK-APC) in 1971.
In 1993, Professor David Vaughan of the British Antarctic Survey (BAS) predicted that the northern part of the Wilkins ice shelf was likely to be lost within 30 years if climate warming on the Peninsula were to continue at the same rate.[2]
A study by the National Academy of Sciences in 2002 stated, "Because air temperatures are statistically increasing along the Antarctic Peninsula region, the presence of glacial meltwater is likely to become more prevalent in these surface waters and continue to play an ever-increasing role in driving this fragile ecosystem." In 2008 David Vaughan conceded his predictions had been too conservative and that events on the ground were moving quicker than he anticipated.[3]
On 25 March 2008 a 405km2 (156sqmi) chunk of the Wilkins ice shelf disintegrated, putting an even larger portion of the glacial ice shelf at risk.[4][5] Scientists were surprised when they discovered the rest of the 14,000km2 (5,400sqmi)[6] ice shelf is beginning to break away from the continent. What is left of the Wilkins ice shelf is now connected by only a narrow beam of ice.[7] At the end of May 2008, another break-off further reduced the width of the connecting ice strip from 6to 2.7km (3.7–1.7mi).[8] This second smaller event, with about 160km2 (62sqmi) of ice separating, was the first documented break-up that occurred in winter.[8] The Wilkins Ice Shelf is not connected to inland glaciers in the same way as the Larsen B Ice Shelf was and will therefore have a negligible effect on sea level rise.[7]
On 29 November 2008, the European Space Agency (ESA) announced that the Wilkins Ice Shelf has lost around 2,000 square kilometres (770sqmi) so far in 2008. A satellite image captured 26 November 2008 shows new rifts on the ice shelf that make it dangerously close to breaking away from the strip of ice—and the islands to which it is connected, the ESA said.[9]
On 20 January 2009, Reuters reported that the ice shelf could collapse into the ocean within "weeks or months". The shelf was then only held up by a very thin strip of ice (varying from 2km to 500 meters at the narrowest), which made it very vulnerable to cracks and fissures. If the strip were to break, it would release the ice shelf, which now has the area of the state of Connecticut (about 14,000km2).[10] Satellite evidence from 2 April 2009 led ESA analysts to conclude that the collapse of the strip (which would result in a partial break-away from the Antarctic Peninsula) was "imminent".[11] Pursuant to this determination, ESA's Envisat satellite is observing the area on a daily basis. The satellite acquisitions are updated automatically to monitor the developments immediately as they occur.[12] Additionally NASA's Terra and Aqua satellites overfly the area several times a day and some of the images acquired are also available.[13]
On 5 April 2009, the ice bridge connecting part of the ice shelf to Charcot Island collapsed.[14] The break occurred at the thinnest point in the 40-kilometre-long (25mi) bridge and was the first in any of the sections that connect it to the mainland.[15] While only a section has broken away, some scientists predicted that another large section of the Wilkins Ice Shelf was only days away from completely breaking off.[16] The shelf remains connected to Latady Island, although it has been stated that this connection "looks set to collapse" as well.[17] The breakaway is seen as firm evidence of the ongoing effects of warming.[18] Temperatures in this region of Antarctica have risen by 2.5 degrees Celsius since the 1950s.[17] Some scientists believe that the collapse of the weakened ice was triggered by increased wave action due to the current relative absence of sea ice, however, a prominent glaciologist, Doug MacAyeal, has said the trigger for the original break-up in March 2008 was likely the much longer wavelengths of ocean swells created by distant storms.[19]
If the entire shelf, which is approximately the size of Jamaica (10,991km2, 4,244 sq mi),[15] does completely break away from land it would be the largest one to do so, thus far.[16] In the month of April 2009 alone, approximately 700 square kilometers (about 270.3 square miles) has broken off Wilkins Sound since the collapse of the ice bridge.[20]
The disintegration of the fringe of the ice shelf, weakened by previous breakups, has continued in March 2013.[21]
The Wilkins ice bridge still intact.
The ice bridge is gone, replaced by chunks of ice.
An iceberg is a piece of freshwater ice more than 15 m long that has broken off a glacier or an ice shelf and is floating freely in open (salt) water. Smaller chunks of floating glacially derived ice are called "growlers" or "bergy bits". Much of an iceberg is below the water's surface, which led to the expression "tip of the iceberg" to illustrate a small part of a larger unseen issue. Icebergs are considered a serious maritime hazard.
The Ross Ice Shelf is the largest ice shelf of Antarctica. It is several hundred metres thick. The nearly vertical ice front to the open sea is more than 600 kilometres (370 mi) long, and between 15 and 50 metres high above the water surface. Ninety percent of the floating ice, however, is below the water surface.
An ice shelf is a large 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 is referred to as the grounding line; the boundary between the ice shelf and the open ocean is the ice front or calving front.
The Filchner–Ronne Ice Shelf or Ronne–Filchner Ice Shelf is an Antarctic ice shelf bordering the Weddell Sea.
The Antarctic Peninsula, known as O'Higgins Land in Chile and Tierra de San Martín in Argentina, and originally as Graham Land in the United Kingdom and the Palmer Peninsula in the United States, is the northernmost part of mainland Antarctica.
The Larsen Ice Shelf is a long ice shelf in the northwest part of the Weddell Sea, extending along the east coast of the Antarctic Peninsula from Cape Longing to Smith Peninsula. It is named after Captain Carl Anton Larsen, the master of the Norwegian whaling vessel Jason, who sailed along the ice front as far as 68°10' South during December 1893. In finer detail, the Larsen Ice Shelf is a series of shelves that occupy distinct embayments along the coast. From north to south, the segments are called Larsen A, Larsen B, and Larsen C by researchers who work in the area. Further south, Larsen D and the much smaller Larsen E, F and G are also named.
The Brunt Ice Shelf borders the Antarctic coast of Coats Land between Dawson-Lambton Glacier and Stancomb-Wills Glacier Tongue. It was named by the UK Antarctic Place-names Committee after David Brunt, British meteorologist, Physical Secretary of the Royal Society, 1948–57, who was responsible for the initiation of the Royal Society Expedition to this ice shelf in 1955.
Iceberg B-15 was the largest recorded iceberg by area. It measured around 295 by 37 kilometres, with a surface area of 11,000 square kilometres, about the size of the island of Jamaica. Calved from the Ross Ice Shelf of Antarctica in March 2000, Iceberg B-15 broke up into smaller icebergs, the largest of which was named Iceberg B-15-A. In 2003, B-15A drifted away from Ross Island into the Ross Sea and headed north, eventually breaking up into several smaller icebergs in October 2005. In 2018, a large piece of the original iceberg was steadily moving northward, located between the Falkland Islands and South Georgia Island. As of August 2023, the U.S. National Ice Center (USNIC) still lists one extant piece of B-15 that meets the minimum threshold for tracking. This iceberg, B-15AB, measures 20 km × 7 km ; it is currently grounded off the coast of Antarctica in the western sector of the Amery region.
Charcot Island or Charcot Land is an island administered under the Antarctic Treaty System, 56 kilometres (30 nmi) long and 46 kilometres (25 nmi) wide, which is ice covered except for prominent mountains overlooking the north coast. Charcot Island lies within the Bellingshausen Sea, 102 kilometres (55 nmi) west of Alexander Island, and about 57 kilometres (31 nmi) north of Latady Island. A notable landmark of the island is its northernmost point, Cape Byrd.
Latady Island is a low ice-covered island off Antarctica, about 35 nmi (65 km) long and 10 nmi (20 km) wide, lying 45 nmi (85 km) south of Charcot Island and west of Alexander Island. An ice-covered feature in this approximate position was seen from the air and described by Sir Hubert Wilkins in 1929, but not recognized as an island or separately mapped. Latady Island was first photographed from the air by the Ronne Antarctic Research Expedition (RARE), 1947–1948, and mapped from these photos by D. Searle of the Falkland Islands Dependencies Survey in 1960. it was named by the UK Antarctic Place-Names Committee for William R. Latady, an aerial photographer and navigator on the RARE flight.
Rothschild Island is a black rugged island 39 kilometres (24 mi) long, mainly ice-covered but surmounted by prominent peaks of Desko Mountains in Antarctica, 8 kilometres (5 mi) west of the north part of Alexander Island in the north entrance to Wilkins Sound.
Pine Island Glacier (PIG) is a large ice stream, and the fastest melting glacier in Antarctica, responsible for about 25% of Antarctica's ice loss. The glacier ice streams flow west-northwest along the south side of the Hudson Mountains into Pine Island Bay, Amundsen Sea, Antarctica. It was mapped by the United States Geological Survey (USGS) from surveys and United States Navy (USN) air photos, 1960–66, and named by the Advisory Committee on Antarctic Names (US-ACAN) in association with Pine Island Bay.
Thwaites Glacier is an unusually broad and vast Antarctic glacier located east of Mount Murphy, on the Walgreen Coast of Marie Byrd Land. It was initially sighted by polar researchers in 1940, mapped in 1959–1966 and officially named in 1967, after the late American glaciologist Fredrik T. Thwaites. The glacier flows into Pine Island Bay, part of the Amundsen Sea, at surface speeds which exceed 2 kilometres (1.2 mi) per year near its grounding line. Its fastest-flowing grounded ice is centered between 50 and 100 kilometres east of Mount Murphy. Like many other parts of the cryosphere, it has been adversely affected by climate change, and provides one of the more notable examples of the retreat of glaciers since 1850.
The retreat of glaciers since 1850 is well documented and is one of the effects of climate change. The retreat of mountain glaciers, notably in western North America, Asia, the Alps and tropical and subtropical regions of South America, Africa and Indonesia, provide evidence for the rise in global temperatures since the late 19th century. The acceleration of the rate of retreat since 1995 of key outlet glaciers of the Greenland and West Antarctic ice sheets may foreshadow a rise in sea level, which would affect coastal regions. Excluding peripheral glaciers of ice sheets, the total cumulated global glacial losses over the 26-year period from 1993 to 2018 were likely 5500 gigatons, or 210 gigatons per yr.
The Ayles Ice Shelf was one of six major ice shelves in Canada, all on the north coast of Ellesmere Island, Nunavut. The ice shelf broke off from the coast on August 13, 2005, forming a giant ice island 37 m (121 ft) thick and measuring around 14 by 5 km in size. The oldest ice in the ice shelf is believed to be over 3,000 years old. The ice shelf was at, approximately 800 km (500 mi) south of the North Pole.
The Ellesmere Ice Shelf was the largest ice shelf in the Arctic, encompassing about 9,100 square kilometres of the north coast of Ellesmere Island, Nunavut, Canada. 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. The continuous mass of the Ellesmere Ice Shelf had been in place for at least 3,000 years.
Ice calving, also known as glacier calving or iceberg calving, is the breaking of ice chunks from the edge of a glacier. It is a form of ice ablation or ice disruption. It is the sudden release and breaking away of a mass of ice from a glacier, iceberg, ice front, ice shelf, or crevasse. The ice that breaks away can be classified as an iceberg, but may also be a growler, bergy bit, or a crevasse wall breakaway.
A-38 was a large iceberg that split from the Filchner-Ronne Ice Shelf in Antarctica in October 1998. Soon after formation it split into two pieces, A-38A and A-38B, which drifted westwards on the Weddell Gyre. The icebergs moved north along the Antarctic Peninsula and reached its tip in February 2003. A-38A and A-38B increased speed in open sea and grounded in shallower waters to the east of South Georgia Island in December 2003. A-38A broke up into three pieces in March 2004 and drifted north where it decayed. A-38B split into two in April, with the eastern portion, now known as A-38G, drifting north and west to decay. The remainder of A-38B remained grounded, interfering with the foraging routes of seals and penguins in South Georgia, resulting in the deaths of their young. On 20 August A38-B broke into two, with the new portion drifting north and breaking up. The remainder of A-38B continued to break up through September 2004 and had completely decayed by 2005.
Iceberg A-68 was a giant tabular iceberg adrift in the South Atlantic, having calved from Antarctica's Larsen C ice shelf in July 2017. By 16 April 2021, no significant fragments remained.
In mid-May 2021, A-76 was, before it broke into three, the world's largest floating iceberg, calved from the Filchner–Ronne Ice Shelf in Antarctica.
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