For 30 years this trillion-tonne iceberg didn’t move an inch, then it finally did

You’d think something as massive as A23a would slowly drift across the ocean from the moment it broke off. Instead, it stayed put. Soon after separating from Antarctica’s Filchner Ice Shelf in 1986, the iceberg got stuck on the seabed in the Weddell Sea and remained there for almost three decades, almost as if it had anchored itself to the ocean floor.

Then, in 2022, it finally came loose. Scientists who had watched it for years suddenly had something exciting to follow, as the iceberg drifted more than 2,300 kilometres through Antarctic waters and into the South Atlantic.

At its largest, A23a covered around 3,500 square kilometres — bigger than Goa, roughly twice the size of London, and nearly three times the size of New York City — with a weight estimated close to one trillion tonnes.

By March this year, the iceberg had shrunk to just 170 square kilometres. In April, satellites captured one of its last images, and soon after, there was nothing left big enough to spot from space, closing the story of one of Earth’s most extraordinary ice giants after nearly 40 years.

Image: Wikimedia Commons/by NASA MODIS Land Rapid Response Team