Английская Википедия:Iceberg A-68

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Файл:A-68D calving.gif

Файл:Iceberg A-68 - July 20 2017.jpg

Iceberg A-68 on 20 July 2017

Файл:TheDriftOfA68.gif

The drift of Iceberg A-68A from 1 May 2018 to 26 August 2018

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.

With a surface area of Шаблон:Convert, twice the size of Luxembourg, over a quarter the size of Wales, and larger than Delaware, it was one of the largest recorded icebergs, the largest being B-15 which measured Шаблон:Convert before breaking up. The calving of Шаблон:Nowrap reduced the overall size of the Larsen C shelf by 12 percent.

Historical data shows that many icebergs that break off from the Antarctic Peninsula reach South Georgia and the South Sandwich Islands.

The name Шаблон:Nowrap was assigned by the US National Ice Center. It broke into parts with the mother berg dubbed Шаблон:Nowrap. The larger child icebergs were designated in order of birthing, as Шаблон:Nowrap, Шаблон:Nowrap, Шаблон:Nowrap, Шаблон:Nowrap, Шаблон:Nowrap, and in January 2021, splitting almost in half to birth Шаблон:Nowrap. On 30 January 2021, Iceberg Шаблон:Nowrap broke into other icebergs called Шаблон:Nowrap, Шаблон:Nowrap, Шаблон:Nowrap, Шаблон:Nowrap, Шаблон:Nowrap, Шаблон:Nowrap.

History and recent developments

A-68 was part of Larsen C, a section of the Larsen Ice Shelf. Scientists found the crack beginning to form in November 2016. Scientists assess that A-68 "didn't just break through in one clean shot, [but] it formed a lace-network of cracks first." The resulting iceberg was around Шаблон:Convert long and Шаблон:Convert wide, Шаблон:Convert in area, Шаблон:Convert thick and weighed an estimated one trillion tonnes.

Satellite images from the ESA and EU's Copernicus Program show that as the iceberg moved, it was gradually shrinking and splintering, forming more icebergs in the process.

Scientists are looking into the possibility of the ice shelf collapsing as a result of the split with A-68, or whether the iceberg was the "cork" for Larsen C that allows ice to flow more freely into the sea, thereby contributing to rising sea levels.

Post November 2017, satellite images showed that A-68 was slowly drifting northward, with a widening gap to the main shelf. The gap was approximately Шаблон:Convert wide and contained a thin layer of loose, floating ice and a cluster of more than 11 'smaller' bergs, one much larger than the others.Шаблон:Citation needed

A British expedition on Шаблон:Ship intended to sample the marine life at the A-68 cleavage line in March 2018, but had to turn back due to thick sea ice. During 2018, A-68 continued to drift northwards. In 2018 or 2019, a large chunk almost 14 km × 8 km (9 miles × 5 miles) broke off and was named A-68B, with the mother iceberg now being A-68A.

On 6 February 2020, A-68A began moving into open waters. On 23 April 2020, a chunk measuring about 175 sq. km. (70 sq. mi.) broke off the iceberg and was named A-68C.

On 4 November 2020, it was reported that A-68A was approaching South Georgia Island and that there was a strong possibility that the iceberg might run aground on the shallower continental shelf near the island, posing a grave threat to local penguins and seals. A spokesman from the British Antarctic Survey stated that the iceberg could become stuck for a number of years, causing disruption to wildlife and the local fishing industry.

On 9 December 2020, the Royal Air Force released video footage of A-68A, 150 km off South Georgia. The RAF conducted reconnaissance flights over the iceberg on 18 November and 5 December 2020.

Шаблон:Asof, a part of the iceberg was just Шаблон:Cvt from South Georgia, but the concern seemed to have lessened. National Geographic reported that "[s]cientists expect the iceberg ... to either anchor in the shallow waters around the island or move past it in the coming days." On this date it was also reported that a corner had been knocked off A-68A, most likely due to impact with the seabed. The new free floating iceberg has been designated A-68D.

On 22 December 2020, images from ESA's Sentinel-1 radar satellite showed that A-68A had experienced a major break-up. Two of the larger fragments were named A-68E and A-68F. A modeling study demonstrated that this break-up was likely triggered when part of A-68A became positioned within stronger ocean currents than the rest of the berg, generating enough tension along its body to break it into pieces.

On 28 January 2021, Sentinel-1 discovered that the southern third of A-68A had broken away. The new segment was named A-68G, with an area of around Шаблон:Convert. The imagery shows these two bergs around 135 km south-east of South Georgia drifting close together.

On 30 January 2021, Iceberg A-68A broke up into other icebergs called A-68H, A-68I, A-68J, A-68K, A-68L, and A-68M.

On 15 February 2021, it was reported that British scientists had arrived at the remnants of A-68A, and had deployed a robotic glider to measure seawater salinity, temperature and chlorophyll close to the remaining blocks of ice to ascertain effects on local marine life.

On 16 April 2021, the largest fragment was down to 3 nautical miles in length and the U.S. National Ice Center, which names, tracks, and documents Antarctic icebergs, discontinued tracking, as the Center only studies icebergs that are at least 20 sq. nautical miles, or that measure 10 nautical miles on the longest axis.

Gallery

• Radar imagery from Sentinel-1B taken on 12 July 2017, showing the complete break

  Radar imagery from Sentinel-1B taken on 12 July 2017, showing the complete break

• A-68 on 12 July 2017

  A-68 on 12 July 2017

• Close-up of A-68 on 20 July 2017

  Close-up of A-68 on 20 July 2017

• Close-up of A-68 on 9 December 2019

  Close-up of A-68 on 9 December 2019

• A-68A location on 9 February 2020

  A-68A location on 9 February 2020

• MS World Explorer at Шаблон:Nowrap (with spyhopping humpback whale) in the Weddell Sea, 10 March 2020

  MS World Explorer at Шаблон:Nowrap (with spyhopping humpback whale) in the Weddell Sea, 10 March 2020

• A-68A in open waters on 5 July 2020

  A-68A in open waters on 5 July 2020

External links

• Шаблон:Commons category-inline
• Шаблон:Cite web
• Шаблон:Cite web