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Antarctica iceberg A23a: Where is it now and does it pose any threat?


Satellite image of the Antarctic iceberg A23a in November 2023

European Union/Copernicus Sentinel-3 via Reuters

The largest iceberg in the world is on the move after being stuck in the Antarctic sea floor for nearly 40 years. Known as A23a, the iceberg has now floated beyond the northernmost point of Antarctica and is on its way to melt in warmer waters.

Where is the iceberg now?

It is just north of the tip of the Antarctic Peninsula, which extends from West Antarctica towards South America. Satellite imagery provided by the British Antarctic Survey shows the iceberg wending its way through the Weddel Sea in the Southern Ocean throughout 2022 and 2023, pushed by currents and winds across thousands of kilometres. The mass of ice reached just beyond the Antarctic Peninsula in late November.

Most icebergs from the Weddel Sea end up carried by currents into the South Atlantic’s “iceberg alley” where they eventually melt.

When did it start moving?

The iceberg first calved off the Filchner Ice Shelf in West Antarctica in 1986, but it immediately ran aground on the ocean floor, remaining in place for more than 30 years. Then in 2020 Andrew Fleming at the British Antarctic Survey noticed it was beginning to move, he told the BBC.

“Eventually it was going to decrease [in size] sufficiently to lose grip and start moving,” he told the outlet.

How big is the iceberg?

It covers nearly 4000 square kilometres, an area more than four times as big as New York City. It is around 400 metres (more than 1300 feet) thick.

While this makes it the largest iceberg now bobbing in the world’s oceans, it is not the largest on record. That behemoth, known as A-76, measured 4320 square kilometres when it broke off from West Antarctica in 2021.

Does the iceberg pose any threat?

The iceberg does not pose a threat to people, although it may become a problem for wildlife, such as penguins or seals, if it runs aground in their feeding or breeding grounds in the Southern Ocean.

Is the movement of the iceberg linked to climate change?

Fleming told the BBC that researchers do not think there is a clear link between the iceberg’s recent movement and warmer waters driven by climate change.

However, researchers have been shocked by recent climate extremes in Antarctica, including record high temperatures and vast areas of missing sea ice, which serve to buffer the continent’s ice shelves from warmer water and waves.

After reaching a record low in 2022, sea ice around the continent did not recover as much as usual this year, remaining far below average into the southern winter. In September, Antarctic sea ice set a new record when it reached a maximum extent that was more than a million square kilometres below the previous record low set in 1986.

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