World’s biggest iceberg, A23a, is on the move again

The world’s largest iceberg is on the move again, drifting through the Southern Ocean after months stuck spinning on the same spot, scientists from the British Antarctic Survey (BAS) have said.

Spanning an area of 3,672 square kilometres (1,418-square-miles) when measured in August – slightly bigger than Rhode Island – the A23a iceberg has been carefully tracked by scientists ever since it calved from the Filchner-Ronne ice shelf in 1986.

It remained grounded on the Antarctic’s Weddell Sea floor for more than 30 years, probably until it shrank just enough to loosen its grip on the seafloor.

Then, the iceberg was carried away by ocean currents before it became stuck again in a Taylor column – the name given to a spinning vortex of water caused by ocean currents hitting an underwater mountain.

Now that the iceberg has broken free, scientists expect it will continue drifting along the ocean currents toward warmer water and the remote island of South Georgia, where it is likely to break up and eventually melt, BAS said in a statement published Friday.

A23a has held the “largest current iceberg” title several times since the 1980s, occasionally being surpassed by larger but shorter-lived icebergs, including A68 in 2017 and A76 in 2021.

Scientists have said that, while this particular iceberg probably broke away as part of the natural growth cycle of the ice shelf and won’t contribute to rising sea levels, climate change is driving worrying changes in this vast, isolated continent, with potentially devastating consequences for global sea level rise.

Throughout the iceberg’s journey, scientists have studied its erosion as well as the ways in which sea ice can influence global ocean cycles of carbon and nutrients.

“We know that these giant icebergs can provide nutrients to the waters they pass through, creating thriving ecosystems in otherwise less productive areas,” Laura Taylor, a biogeochemist who collected samples from the water around the iceberg, said in the BAS statement.

“What we don’t know is what difference particular icebergs, their scale, and their origins can make to that process.

“We took samples of ocean surface waters behind, immediately adjacent to, and ahead of the iceberg’s route. They should help us determine what life could form around A23a and how it impacts carbon in the ocean and its balance with the atmosphere.”