Iceberg A-68

Iceberg A-68
Tabular iceberg
A-68A on 18 November 2020
Part of	Larsen C ice shelf (originally)
Offshore water bodies	South Atlantic
Area
• Total	5,800 km2 (2,200 sq mi) (at break)
Dimensions
• Length	175 km (109 mi) (at break)
• Width	50 km (31 mi) (at break)

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.^[1][2][3] By 16 April 2021, no significant fragments remained.^[4]

With a surface area of 5,800 square kilometres (2,200 sq mi), twice the size of Luxembourg, over a quarter the size of Wales, and larger than Delaware,^[5] it was one of the largest recorded icebergs, the largest being B-15 which measured 11,000 square kilometres (4,200 sq mi) before breaking up. The calving of A-68 reduced the overall size of the Larsen C shelf by 12 percent.^[5][6]

Historical data shows that many icebergs that break off from the Antarctic Peninsula reach South Georgia and the South Sandwich Islands.^[7]

The name "A-68" was assigned by the US National Ice Center. It broke into parts with the mother berg dubbed A-68A. The larger child icebergs were designated in order of birthing, as A-68B, A-68C, A-68D, A-68E, A-68F, and in January 2021, splitting almost in half to birth A-68G. On 30 January 2021, Iceberg A-68A broke into other icebergs called A-68H, A-68I, A-68J, A-68K, A-68L, A-68M.

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."^[5] The resulting iceberg was around 175 km (574,000 ft) long and 50 km (160,000 ft) wide, 5,800 km² (2,200 sq mi) in area, 200 m (660 ft) thick and weighed an estimated one trillion tonnes.^[8][5]

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.^[9]

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.^[10]

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 five kilometers (3.1 miles) 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.^{[citation needed]}

A British expedition on RRS James Clark Ross 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.^[11] During 2018, A-68 continued to drift northwards.^[12] 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.^[13]

On 6 February 2020, A-68A began moving into open waters.^[14] On 23 April 2020, a chunk measuring about 175 sq. km. (70 sq. mi.) broke off the iceberg and was named A-68C.^[15]

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.^[16]

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.^[17]

As of 17 December 2020^[update], a part of the iceberg was just 50 km (31 mi) 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."^[18] On this date it was also reported that a corner had been knocked off A-68A, most likely due to impact with the seabed.^[19] The new free floating iceberg has been designated A-68D.^[20]

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.^[21] 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.^[22]

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 950 square kilometres (370 sq mi). The imagery shows these two bergs around 135 km south-east of South Georgia drifting close together.^[23][24]

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.^[25][26]

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.^[27]

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,^[4] as the Center only studies icebergs that are at least 20 sq. nautical miles, or that measure 10 nautical miles on the longest axis.^[28]

• 
  Radar imagery from Sentinel-1B taken on 12 July 2017, showing the complete break
• 
  A-68 on 12 July 2017
• 
  Close-up of A-68 on 20 July 2017
• 
  Close-up of A-68 on 9 December 2019
• 
  A-68A location on 9 February 2020
• 
  MS World Explorer at A-68A (with spyhopping humpback whale) in the Weddell Sea, 10 March 2020
• 
  A-68A in open waters on 5 July 2020

• Media related to Iceberg A-68 at Wikimedia Commons
• "Navigating Along Iceberg A68A Aboard HANSEATIC nature". Ship Videos. 14 December 2019.
• "An RAF A400M from BFSAI has conducted reconnaissance of the A68a iceberg". FaceBook. BFSAI. 4 December 2020.