Shrouded in snow and fog, expedition leader Ian Strachan knew his ship was approaching a colossal presence in the Antarctic seas. As the clouds lifted, a vast, almost abstract white line stretched across the horizon—the world’s largest iceberg, A23a.
“Then the clouds lifted and we could see this expansive—almost abstract—white line that extended each way across the horizon,” Strachan described. As they drew nearer on Sunday, immense crevasses and striking blue arches carved into the iceberg’s edge became visible.
Waves reaching up to four meters slammed against its walls, breaking off small chunks and causing some arches to collapse. Strachan likened sailing alongside the endless jagged edge to observing sheet music: “All the cracks and arches were different notes as the song played.”
Tooth-shaped and spanning nearly 4,000 square kilometers—more than twice the size of Greater London—A23a is now drifting northward after spending three decades grounded on the Antarctic ocean floor.
Estimated to contain one trillion tonnes of fresh water, the iceberg is up to 400 meters thick in places. Currently, it is drifting between Elephant Island and the South Orkney Islands.
A23a broke off from the Antarctic coast in 1986, making it not only the world’s largest but also its oldest iceberg. However, it remained stuck to the ocean floor for decades until satellite images in 2020 suggested it was “wobbling,” according to Andrew Fleming of the British Antarctic Survey.
Late last year, A23a finally broke free, commencing its journey northward. While the exact cause remains uncertain, Fleming noted that such iceberg movements are part of natural processes, though they occur within a system undergoing dramatic changes.
Since its release, A23a has followed a path known as “iceberg alley,” moving past the east side of the Antarctic Peninsula through the Weddell Sea. Warmer waters and stronger waves are expected to gradually break it apart as it ventures into the Southern Ocean.
If it continues on a similar path to previous massive icebergs like A68 and A76, A23a may drift toward South Georgia Island in the South Atlantic Ocean, a critical habitat for wildlife such as penguins and seals. While there is a concern that the iceberg could impede these animals’ access to foraging areas, it is more likely to move around the island and continue its northward drift.
Some icebergs have journeyed so far north that they have been spotted from the Brazilian coast. However, A23a’s ultimate fate, like all icebergs venturing into warmer waters, is to melt away. “Ultimately, they’re doomed,” Fleming remarked.
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World's biggest iceberg 'battered' by waves as it heads north
cgtn.com
