“Its time has come”: In Antarctica, the largest iceberg in the world is drifting

2024-01-20 07:26:00

It was impossible to see it that day through the thick fog of the Antarctic seas, but Ian Strachan, expedition leader, knew that his ship was approaching an icy behemoth: the largest iceberg in the world was floating somewhere in front of him.

In this photo provided by the British Antarctic Survey, a view of the A23a iceberg is seen from the RRS Sir David Attenborough, Antarctica, Friday December 1, 2023. (T. Gossman, M. Gascoyne, C. Grey/British Antarctic Survey via AP)

KEYSTONE

As his ship moved forward, huge gaping crevices and magnificent blue arcs appeared, carved into the ice wall. Some arches had collapsed under the blows of waves four meters high, he describes.

The tooth-shaped iceberg, named A23a, measures nearly 4,000 square kilometers. Its weight is estimated at nearly a thousand billion tons and its thickness reaches 400 meters in certain places. Heading towards the north of the Southern Ocean, it is currently located between Elephant Island and the South Orkney Islands.

Ian Strachan’s private expedition, managed by the company EYOS expeditions, was not the first to witness the spectacle. Last December, the British polar research vessel RRS Sir David Attenborough was carrying out a scientific mission to Antarctica when A23a blocked its path.

The leader of the expedition, Andrew Meijers, remembers this “magical moment” as he approached the iceberg, the sun appearing, a group of orcas swimming past… “It took us six hours to overtake it, at full steam,” says this scientist from the British Antarctic Survey.

“His time has come”

The A23a iceberg first broke off the Antarctic coast in 1986, making it both the oldest and largest in the world. But it quickly found itself stuck on ocean shoals, where it stagnated for three decades.

In 2020, Andrew Fleming, also of the British Antarctic Survey, saw satellite images suggesting the giant was “wobbly”. A23a finally broke free late last year, and began venturing north.

The question of a link with climate change – Antarctica’s winter sea ice reached a record low in 2023 – remains open. According to Andrew Meijers, this is like trying to attribute a single fire or flood to global warming.

Andrew Fleming nevertheless specifies that the formation of this type of iceberg is a natural process and that each year, one or two immense blocks of ice break away from the white continent. “It is more likely that his time has come” and that he will live out his final months, thinks Andrew Fleming. The “big beast”, as he calls it, moves forward at a walking pace. “The Titanic would have had time to see it coming.”

Font in vue

Since A23a broke away from the White Continent, it has followed more or less the same trajectory as the previous massive icebergs A68 and A76: passing the eastern side of the Antarctic Peninsula and the Weddell Sea, along a road known as the “iceberg corridor”. Warmer waters and larger waves will likely break it on its way, explains Andrew Fleming.

If he follows in the footsteps of his two predecessors, he will head towards the island of South Georgia, which is home to very rich wildlife such as penguins and seals. This raises a slight concern because if the iceberg were to park near the island, it might prevent these animals from accessing their usual feeding place. However, this is an unlikely scenario.

The A68 iceberg had instead broken up into small pieces, making navigation difficult for fishing boats, Andrew Meijers explained. It is therefore more likely that A23a drifts around the island and continues to meander north. And eventually melts into warmer waters, like all icebergs heading in that direction.

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