Iceberg A-68 was a large, flat-shaped iceberg floating freely in the South Atlantic Ocean. It broke off from Antarctica's Larsen C ice shelf in July 2017. By April 16, 2021, no large pieces of the iceberg remained.

The iceberg had a surface area of 5,800 square kilometers (2,200 square miles), which is about twice the size of Luxembourg, a quarter the size of Wales, and larger than Delaware. It was one of the largest recorded icebergs. The largest iceberg ever recorded was B-15, which measured 11,000 square kilometers (4,200 square miles) before breaking apart. The loss of A-68 reduced the total size of the Larsen C ice shelf by 12 percent.

Historical records show that many icebergs that break off from the Antarctic Peninsula travel to South Georgia and the South Sandwich Islands.

The name "A-68" was given by the US National Ice Center. After breaking apart, the main piece was called A-68A. The other large pieces were named in the order they separated: A-68B, A-68C, A-68D, A-68E, and A-68F. In January 2021, A-68A split nearly in half to form A-68G. On January 30, 2021, A-68A further split into smaller icebergs named A-68H, A-68I, A-68J, A-68K, A-68L, and A-68M.

History and recent developments

A-68 was part of Larsen C, a section of the Larsen Ice Shelf. Scientists discovered the crack forming in November 2016. They believe A-68 did not break all at once but instead formed a network of cracks first. The iceberg was about 175 km (574,000 ft) long, 50 km (160,000 ft) wide, covered an area of 5,800 km (2,200 mi), was 200 m (660 ft) thick, and weighed about one trillion tonnes.

Satellite images from the ESA and EU’s Copernicus Program show that as the iceberg moved, it slowly became smaller and broke into more icebergs.

Scientists studied whether the split with A-68 might cause the ice shelf to collapse or if the iceberg acted as a "cork" that allowed ice to flow more freely into the sea, possibly increasing sea levels.

After November 2017, satellite images showed A-68 drifting northward, with a gap of about five kilometers (3.1 miles) between it and the main shelf. This gap contained floating ice and more than 11 smaller icebergs, one much larger than the rest.

A British expedition on the RRS James Clark Ross planned to study marine life near the A-68 cleavage line in March 2018 but had to return because of thick sea ice. In 2018, A-68 continued drifting northward. Around 2018 or 2019, a large piece measuring about 14 km × 8 km (9 miles × 5 miles) broke off and was named A-68B, with the original iceberg now called A-68A.

On 6 February 2020, A-68A entered open waters. On 23 April 2020, a piece about 175 square kilometers (70 square miles) broke off and was named A-68C.

On 4 November 2020, it was reported that A-68A was approaching South Georgia Island and might run aground near the island, which could harm penguins and seals.

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

By 17 December 2020, part of A-68A was 50 km (31 mi) from South Georgia, but concerns had decreased. National Geographic reported that scientists expected the iceberg to either stop near the island or move past it. On this date, it was also reported that a corner of A-68A had broken off, likely due to hitting the seabed, and the new iceberg was named A-68D.

On 22 December 2020, satellite images showed A-68A breaking into two large pieces named A-68E and A-68F. A study suggested this breakup happened because part of A-68A entered stronger ocean currents, creating tension that caused it to split.

On 28 January 2021, the southern third of A-68A broke away and was named A-68G, covering about 950 square kilometers (370 square miles). These two pieces were about 135 km southeast of South Georgia and were drifting closer together.

On 30 January 2021, A-68A broke into additional icebergs named A-68H, A-68I, A-68J, A-68K, A-68L, and A-68M.

On 15 February 2021, British scientists reached the remaining parts of A-68A and used a robotic glider to measure seawater salinity, temperature, and chlorophyll near the ice to study its effects on marine life.

On 16 April 2021, the largest piece of A-68A was only 3 nautical miles long. The U.S. National Ice Center, which tracks Antarctic icebergs, stopped monitoring A-68A because it no longer met the criteria of being at least 20 square nautical miles or 10 nautical miles long on its longest side.

Gallery

• Radar images from Sentinel-1B taken on 12 July 2017, showing the full separation
• Image of A-68 on 12 July 2017
• Detailed image of A-68 on 20 July 2017
• Detailed image of A-68 on 9 December 2019
• Map showing the position of A-68A on 9 February 2020
• Photograph of the ship MS World Explorer near A-68A (with a humpback whale sticking its head above water) in the Weddell Sea on 10 March 2020
• Image of A-68A in the open ocean on 5 July 2020