- 40 x 34 nautical miles dimension(s)
- Antarctica ()
The record for the largest current iceberg changed hands in December 2020 when the previous record holder (A68A) broke into several fragments as it got perilously close to the island of South Georgia in the South Atlantic. The title now passes to A23A, which is much further south in the Weddell Sea off Antarctica. According to NOAA's National Ice Center which monitors the world's largest icebergs using live satellite data, A23A was 40 nautical miles long and 34 nautical miles wide (77 x 63 km; 48 x 39 mi) as of 8 January 2021, and it had a total area of approximately 4,000 km2 (1,540 sq mi). Unlike the well-travelled A68A, A23A was born from the Filchner Ice Shelf in August 1986, but has only moved around 200 km (125 mi) in 31 years because it is grounded on the sea floor.
A68A held the record for the world’s current largest iceberg since it calved from the Larsen C Ice Shelf in the Antarctic Peninsula in July 2017 and measured 6,000 km2 (2,300 sq mi) - about the size of the US state of Delaware; as of January 2021, it has shrank to 40 x 24 nautical miles (74 x 44 km), with an area of approximately 2,600 km2 (1,000 sq mi).
Thought to be the sixth largest on record, A68A is certainly the most "watched" and, over the last few years, it has travelled thousands of miles through "Iceberg Alley" in the South Atlantic. In December 2020, scientists noticed it was heading straight for South Georgia, which raised concern that it might ground on the shallower sea bed, and potentially disrupt the foraging patterns of marine predators, such as penguins and seals. Satellite observations also showed that it was beginning to disintegrate, with smaller bergs breaking off and, following convention, named A68D, A68E and A68F (A68B and A68C broke away in 2019 and 2020).
The largest iceberg ever reliably documented was approximately 31,000 km2 (12,000 sq mi) – making it larger than Belgium. It was 335 km (208 mi) long and 97 km (60 mi) wide and was sighted 240 km (150 mi) west of Scott Island, in the Southern Ocean by the USS Glacier on 12 November 1956. The precise extent of the iceberg witnessed by the crew of the Glacier was estimated, as they did not have the benefit of satellite photography.