A23a

A23a's course mapped by the NASA Earth Observatory[1]
Satellite images in 2024
Map of A23a (map data)

A23a is a large tabular iceberg which calved from the Filchner–Ronne Ice Shelf in 1986. It was stuck on the sea bed for many years but then started moving in 2020. As of January 2025, its area is about 3,500 square kilometres (1,400 sq mi), which makes it the current largest iceberg in the world.[2][3][4] As of March 2025, it has run aground off South Georgia island.[5]

The base Druzhnaya I, which was originally established on the Filchner–Ronne Ice Shelf, was situated on the iceberg when it calved.[3] Subsequently, a rescue mission was started in 1987 and ultimately moved/renamed the base to Druzhnaya III.[6]

In November 2023, A23a was tracked moving past the northern tip of the Antarctic Peninsula and heading towards the Southern Ocean.[7] On 1 December 2023, the iceberg was intercepted by the polar research ship RRS Sir David Attenborough, off the tip of the Antarctic Peninsula.[8] At 10 knots, it took the ship several hours to sail along two sides of the iceberg.[8] A23a is expected to release a significant quantity of mineral dust as it melts, so the ship took water samples around its perimeter.[8]

On 14 January 2024, dramatic archways caused by wave action on A23a were documented by a drone operated by Eyos Expeditions videographer Richard Sidey and expedition leader Ian Strachan. Their footage was published widely by the BBC and CNN.[9] In early April 2024, the iceberg entered the Antarctic Circumpolar Current but stayed in place as it was trapped in a Taylor column—as confirmed in August 2024—over the Pirie Bank seamount near the South Orkney Islands about 375 miles from the Antarctic Peninsula, turning counterclockwise by around 15 degrees every day.[10][11][12] In December 2024, the British Antarctic Survey (BAS) reported that the iceberg had exited the Taylor column and was now beginning to drift further north through the Southern Ocean.[13]

The BAS expects A23a to follow the Antarctic Circumpolar Current towards the island of South Georgia in the southern Atlantic Ocean, where it will eventually encounter warmer water and break up into smaller icebergs.[14][2] As of 23 January 2025, A23a is 173 miles (278 km) away from South Georgia and still on its way towards the island, potentially threatening the penguin and seal populations by blocking their access to feeding grounds.[2]

On March 4, 2025 it was reported that A23a had grounded 73 km (45 mi) from South Georgia, marking the end of its drift since 2020 before it accelerated and then abruptly stopped near the island.[15] Some scientists say it could threaten local wildlife by blocking key feeding grounds for penguins and seals,[16] though others say they don't expect it to significantly affect wildlife.[15] Scientists warn that its melting could disrupt marine ecosystems by altering nutrient flows and krill populations, though it was also pointed out that its grounding will stir up nutrients from the seafloor and may boost the regional ecosystem.[15] The event underscores the broader impact of climate change on Antarctic ice loss, with researchers closely monitoring its effects on biodiversity and regional stability.[16]

See also

Wikimedia Commons has media related to Satellite pictures of Iceberg A23a.
  • A-76, largest iceberg for several months in 2021
  • B-15, largest recorded iceberg with precise measurements

References

  1. ^ "Antarctic Iceberg Sails Away". NASA Earth Observatory. 28 November 2023.
  2. ^ a b c Rannard, Georgina; Rivault, Erwan (23 January 2025). "Giant iceberg on crash course with island, putting penguins and seals in danger". BBC News. Retrieved 23 January 2025.
  3. ^ a b Amos, Jonathan (24 November 2023). "A23a: World's biggest iceberg on the move after 30 years". BBC News.
  4. ^ "Largest iceberg (current)". Guinness World Records. 23 February 2024. Retrieved 14 December 2024.
  5. ^ "World's largest iceberg runs aground off remote island". BBC News. 4 March 2025. Retrieved 4 March 2025.
  6. ^ Shabad, Theodore (22 February 1987). "Russians Recover Lost Ice Station". The New York Times. Archived from the original on 9 March 2014. Retrieved 4 August 2024.
  7. ^ Smith, Stephen (24 November 2023). "World's largest iceberg – 3 times the size of New York City – "on the move" for the first time in 37 years". CBS News. Retrieved 25 November 2023.
  8. ^ a b c Amos, Jonathan (4 December 2023). "Attenborough ship encounters mammoth iceberg". BBC News.
  9. ^ Amos, Jonathan (16 January 2024). "A23a: Spectacular arches, caves as monster iceberg decays". BBC News. Retrieved 22 January 2024.
  10. ^ Tumin, Remy (7 August 2024). "After Breaking Free, World's Largest Iceberg Is Stuck Spinning in Circles". The New York Times. Archived from the original on 7 August 2024. Retrieved 10 August 2024.
  11. ^ Amos, Jonathan; Rivault, Erwan (4 August 2024). "World's biggest iceberg spins in ocean trap". BBC News. Archived from the original on 4 August 2024.
  12. ^ Kim, Juliana (10 August 2024). "The world's largest iceberg is stuck twirling in an ocean vortex". NPR. Retrieved 14 December 2024.
  13. ^ Sandeman, George (14 December 2024). "World's biggest iceberg heads north after escaping vortex". BBC News. Retrieved 14 December 2024.
  14. ^ "World's largest iceberg A23a breaks free". British Antarctic Survey (Press release). 13 December 2024. Retrieved 14 December 2024.
  15. ^ a b c "Iceberg twice the size of Greater London runs aground near South Georgia". East London and West Essex Guardian Series. 4 March 2025. Retrieved 4 March 2025.
  16. ^ a b "World's largest iceberg runs aground in South Georgia and blocks off key penguin feeding ground". Sky News. Retrieved 4 March 2025.