A23a was one of the largest “megabergs” ever to spawn in our lifetime. When it broke away from the Filchner Ice Shelf and entered the Weddell Sea in West Antarctica in 1986, it covered an area of nearly 4,000 square kilometers – about the size of Hong Kong and Shenzhen combined.
Unlike such stars, A23a has lived a long life, twisting and turning unnoticed across the South Atlantic. For its first 30 years, it accumulated in the Weddell Sea in West Antarctica, the main source of large icebergs. But then the A23a got caught in “Iceberg Alley” and was carried to South Orkney. From there, it was disrupted in a large rotating vortex called the Taylor Row. It orbited the spot for eight months, but eventually split north toward South Georgia, which is home to many of Antarctica’s icebergs.
By early 2025, A23a was still a colossus. It would be too big to pass the space between the island of Taiwan and the coast of mainland China.
But as it travels further north into the warmer parts of the South Atlantic, nature has taken its toll. Over the past few months, it has drifted through the South Atlantic. As of a few months ago, according to Professor Mike Meredith at the British Antarctic Survey in Cambridge, A23a was “getting messy and won’t last long”.
