World’s biggest iceberg drifting towards penguin-packed island

January 24, 2025 journo

The world’s biggest iceberg — a 40-metre-tall wall of ice bigger in area than the Australian Capital Territory — is steadily drifting towards a remote British island off a tip of Antarctica, six weeks after breaking loose from its sea floor grounding.

The slab of ice — named A23a and described as a megaberg — weighs almost one trillion tonnes and could slam into South Georgia Island before either getting stuck or being guided around the land by currents.

A satellite image of a large, four-sided iceberg surrounded by ice and water coloured mostly in white — The world’s largest iceberg, named A23a and pictured via satellite on January 23, has broken free of its sea floor mooring in the Southern Ocean and is gradually drifting towards the British South Georgia Island. (Supplied: US National Ice Center (USNIC))

If it gets stuck, the iceberg could make it hard for parents of baby penguins on the island to feed their young and some could starve.

While scientists and researchers aren’t yet concerned about the potential damage the iceberg could cause, some have voiced their excitement about a natural process involving A23a which they say is happening more frequently because of human-caused climate change.

A blue and white satellite image of a large, four-sided white iceberg floating in dark ocean water surrounded by masses of cloud — The shelf of ice, pictured here via satellite on November 15, 2023, had been connected to the mainland of Antarctica for decades. (Reuters: European Union/Copernicus Sentinel-3)

Calving icebergs are normal, but they are happening more frequently as the climate changes and more fresh water flows into oceans, according to Andrew Meijers, a physical oceanographer with the British Antarctic Survey.

Mr Meijers examined the iceberg up close in December, 2023, when it first drifted past the research ship RRS Sir David Attenborough.

He said for every bit of the iceberg visible above the water’s surface, there was ten-times more ice more below.

The iceberg is making its way at a glacial pace of a metre every three to seven seconds, Mr Meijers said.

In the next two to four weeks, the iceberg will approach South Georgia Island and could be wedged in the shallow shelf off the British territory, or could be diverted around it, according to the oceanographer.

An icy-blue iceberg shelf stretching along a horizon alongside deep blue ocean water — A23a is 40 metres tall, bigger in area than the size of the Australian Capital Territory and weighs almost one trillion tonnes. (Reuters: Rob Suisted/social media)

Eventually, A23a will break up and melt as icebergs typically do, but the bigger concern for researchers now is the impact it could have on penguins in their summer breeding cycle, Mr Meijers said.

Dr Jan Lieser, a marine glaciologist at the University of Tasmania’s Institute for Marine and Antarctic Studies, said the iceberg already appeared to be splitting up.

“There are winds and waves crashing into the sides of the iceberg and that break the iceberg from the side; it is melting from below, and it is developing large rifts, so it might actually split into three or four pieces,” Dr Lieser told the ABC.

“Smaller icebergs will break off it and it will generally continue on a north-eastern trajectory.

Two large blue walls of iceberg pictured alongside each other with rippling deep blue ocean water at their bottom — Researchers say if the shelf of ice collides with South Georgia Island, it could break up into smaller icebergs or it could be diverted entirely around the land. (Reuters: Rob Suisted/social media)

“We have seen other icebergs taking a right-hand turn, just to the south of the island.”

Dr Lieser said that small breakaway icebergs could often pose a danger to shipping vessels that were unable to spot them in the water or via satellite technology, despite the slabs of ice often being in sizes ranging from an office desk to a three-storey house.

This iceberg first broke off from Antarctic in 1986 but has been penned in a crowded patch of sea ice for decades.

On December 13 last year, the British Antarctic Survey announced that the mega iceberg had broken free from its latest sea floor grounding and was drifting in the Southern Ocean.

ABC/AP