A23a, world’s largest iceberg, is now drifting beyond Antarctic waters

A23a, currently the world’s largest iceberg, is on the move after being stuck to the ocean floor for more than three decades. Estimated to have an area approximately 1.5 times the size of the National Capital Territory of Delhi, and weighing almost 1 trillion tonnes (European Space Agency, ESA), A23a is presently heading out of the Weddell Sea. It will enter the Southern Ocean where it will melt and disappear eventually.

While scientists believe the iceberg’s breakaway to be a natural occurrence, they point this to being a stark reminder of the potentially disastrous consequences of global sea level rise.

A23a, which had split from Antarctica’s Filchner Ice Shelf (a large body of floating ice) in August 1986, is now drifting beyond Antarctic waters, on a path known as “iceberg alley”.

Antarctica is a gigantic ice-covered landmass whose melting is resulting in more and more sea level rise each year. Being one of the world’s most important natural laboratories, its white surface helps cool Earth by reflecting energy back into space. But now, darker sea or land is replacing the ice or snow.

“There’s a real danger in the years ahead that Antarctica stops acting as a refrigerant for the planet and starts acting as a radiator,” said Martin Siegert, professor of geosciences and deputy vice-chancellor at the University of Exeter.

After hitting a record low in 2022, sea ice around the continent has remained far below average into the southern winter and did not recover as much as usual this year. The recent extreme climate events in Antarctica, including record-breaking heatwaves and vast areas of missing sea ice, have shocked researchers.

During COP28 this year, World Meteorological Organization Secretary-General Petteri Taalas said: “Sea level rise is record high. Antarctic sea ice is record low. We risk losing the race to save our glaciers and to rein in sea level rise. We cannot return to the climate of the 20th century, but we must act now to limit the risks of an increasingly inhospitable climate in this and the coming centuries.”

The iceberg may pose a threat to wildlife, such as penguins or seals if it runs around in their feeding or breeding grounds in the Southern Ocean.

In 2020, there were similar fears of another giant iceberg, A68, colliding with South Georgia and crushing marine life on the seafloor. But the likelihood of such a catastrophe was avoided when the iceberg broke into smaller chunks.

On the other hand, the melting of these big bergs results in a release of mineral dust that serves as a nutrient source for the organisms that form the base of ocean food chains.