Iceberg A-68

Iceberg A-68 is a giant tabular iceberg adrift in the South Atlantic, having calved from Antarctica's Larsen C ice shelf in July 2017.[1][2][3]

Iceberg A-68 on 20 July 2017
The drift of Iceberg A-68A from 1 May 2018 to 26 August 2018

With a surface area of 5,800 square kilometres (2200 sq. mi.), twice the size of Luxembourg, larger than Delaware and weighing an estimated one trillion tonnes,[4] it is one of the largest recorded icebergs, the largest being B-15 which measured 11,000 square kilometres (4250 sq. mi.) before breaking up. The calving of A-68 reduced the overall size of the Larsen C shelf by 12 percent.[4][5]

Historical data shows that many icebergs that break off from the Antarctic Peninsula reach South Georgia and the South Sandwich Islands.[6]

The name "A-68" was assigned by the US National Ice Center. It has broken into parts with the mother berg dubbed A-68A. The larger child icebergs are 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.

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."[4]

Satellite images from the ESA and EU's Copernicus Program show that as the iceberg moves, it is gradually shrinking and splintering, forming more icebergs in the process.[7]

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.[8]

Since November 2017, satellite images show that A-68 is slowly drifting northward, with a widening gap to the main shelf. The gap was approximately five kilometers (3 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.

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.[9] During 2018, A-68 continued to drift northwards.[10] In 2018 or 2019, a large chunk (almost 14km x 8km; 9 miles x 5 miles) broke off and was named A-68B, with the mother iceberg now being A-68A.[11]

On 6 February 2020, A-68A began moving into open waters.[12] On 23 April 2020, a chunk measuring about 175 sq km (70 sq. mi.) broke off the iceberg and was named A-68C.[13]

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.[14]

On 9 December 2020, the Royal Air Force released video footage of A-68A, 150km off South Georgia. The RAF conducted reconnaissance flights over the iceberg on 18 November and 5 December.[15]

As of 17 December 2020, 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."[16] On this date it was also reported that a corner had been knocked off A-68A, most likely due to impact with the seabed.[17] The new free floating iceberg has been designated A-68D.[18]

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.[19]

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 135km south-east of South Georgia drifting close together.[20][21]

  • 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

References
  1. "Larsen C calves trillion ton iceberg". Project MIDAS. 12 July 2017. Retrieved 12 July 2017.
  2. "Giant iceberg splits from Antarctic". BBC. 12 July 2017.
  3. "Massive iceberg breaks away from Antarctica". CNN. 12 July 2017. Retrieved 13 July 2017.
  4. Davis, Nicola (2 August 2017). "What happened next to the giant Larsen C iceberg?". The Guardian. ISSN 0261-3077. Retrieved 2 August 2017.
  5. McKie, Robin (31 January 2021). "Extraordinary voyage: on the trail of the trillion-tonne runaway iceberg". The Observer. ISSN 0029-7712. Retrieved 31 January 2021.
  6. Mosher, Dave (12 July 2017). "Where Antarctic iceberg from Larsen C shelf might go in Southern Ocean". Business Insider. Retrieved 21 July 2017.
  7. Dvorsky, George. "Antarctica's Massive Iceberg Is Starting to Disintegrate". Gizmodo. Retrieved 2 August 2017.
  8. Becker, Rachel (2 August 2017). "Cracks are still spreading where that massive Antarctic iceberg broke free". The Verge. Retrieved 2 August 2017.
  9. Amos, Jonathan (2 March 2018). "Mission to giant A-68 berg thwarted by sea-ice". BBC News. Retrieved 12 April 2018.
  10. Brandon, Mark. "A trillion tonnes of ice on the move: Iceberg A68A". Mallemaroking. Retrieved 31 August 2018.
  11. Michael Irving (13 July 2020). "Satellites show huge Antarctic iceberg drifted 1,000 km in three years". NewAtlas. Retrieved 13 July 2020.
  12. Amos, Jonathan (5 February 2020). "World's biggest iceberg makes a run for it". BBC News. Retrieved 25 July 2020.
  13. Amos, Jonathan (23 April 2020). "Is the world's biggest iceberg about to break up?". BBC News. Retrieved 28 April 2020.
  14. Amos, Jonathan (4 November 2020). "A68 iceberg on collision path with South Georgia". BBC News. Retrieved 4 November 2020.
  15. Amos, Jonathan (9 December 2020). "RAF releases video of world's biggest iceberg". BBC News. Retrieved 13 December 2020.
  16. The world’s largest iceberg is headed for South Georgia—and its wildlife, National Geographic, 17 December 2020, accessed 18 December 2020.
  17. Amos, Jonathan (17 December 2020). "Giant iceberg A68a prangs seabed and loses corner". BBC News. Retrieved 18 December 2020.
  18. Garrison, Cassandra (17 December 2020). "Massive iceberg pivots, breaks near south Atlantic penguin colony island". Retrieved 18 December 2020.
  19. Amos, Jonathan (22 December 2020). "Giant iceberg A68a shatters into large fragments". BBC News. Retrieved 22 December 2020.
  20. luwi (29 January 2021). "Größter Eisberg der Welt bricht entzwei". science.ORF.at (in German). Retrieved 29 January 2021.
  21. Amos, Jonathan (28 January 2021). "Split signals end for remnant of Antarctic iceberg A68a". BBC News. Retrieved 29 January 2021.
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