Almost 40 years ago, the massive iceberg A23a broke away from the Filchner Ice Shelf in Antarctica. At its peak, it weighed about a trillion tons and covered an area of more than 3,500 km² — twice the size of London. During that time, the ice block became a major obstacle to shipping and a threat to penguin and seal colonies on South Georgia Island.
Today, the iceberg has almost halved in size to 1,770 km², and is about 60 km wide at its widest point. In recent weeks, fragments of about 400 km² have broken off from A23a. Andrew Meyers, a physical oceanographer with the British Antarctic Survey, says the iceberg is “simply rotting” in the warm waters of the Southern Ocean, and the process of disintegration will continue.
A23a had been lying in shallow water in the Weddell Sea for more than three decades before drifting into the South Atlantic in 2020. The iceberg briefly ran aground off South Georgia this spring, raising concerns about the food supply for local penguins and seals. In May, it broke free and began drifting north at speeds of up to 20 km per day.
Scientists say the rapid destruction is caused by a combination of rising ocean temperatures and strong waves. As Meyers points out, icebergs are virtually doomed to collapse once they break away from the ice belt around Antarctica.
Iceberg calving is a natural process, but its frequency is increasing due to global warming caused by anthropogenic emissions. The disappearance of A23a is a reminder of the need to reduce human impact on Earth's ecosystems and control climate change.
