315 billion tonne iceberg the size of Sydney breaks off Antarctic ice shelf

Scientists were surprised a 315 billion tonne iceberg roughly the size of Sydney broke off where it did, but said climate change isn’t to blame.

A 315 billion tonne iceberg roughly the size of Sydney’s urban area has cracked off an Antarctic ice shelf, surprising scientists who expected a separate, smaller iceberg to detach nearby.

The 1636 square kilometre iceberg, named D-28, separated away from the Amery ice shelf in East Antarctica on Saturday, but experts said the separation was overdue.

Scientists from the Australian Antarctic Program, University of Tasmania’s Institute of Marine and Antarctic Studies, and University of California San Diego’s Scripps Institution of Oceanography had been closely monitoring the ice shelf’s “Loose Tooth”, a precariously attached area of ice, for almost two decades.

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They had predicted a large iceberg would break off the shelf sometime between 2010 and 2015, but it’s taken this long for any such separation to occur, and it happened in a different spot than where scientists anticipated.

The iceberg separated from the Amery shelf over the weekend.

“We knew it would happen eventually, but just to keep us all on our toes, it is not exactly where we expected it to be,” said Scripps’ Professor Helen Amanda Fricker, adding she was “excited to see this calving event after all these years”.

“It is like expecting a baby tooth to come out and instead out comes a molar,”

It’s been more than 55 years since the ice shelf, located between two of Australia’s Antarctic research stations, had a major “calving event”.

Researchers are studying the impact of ocean melt and ice flow on the shelf, but Prof Fricker noted the latest separation was a normal part of the cycle, and the team don’t think the iceberg leaving the shelf is linked to climate change.

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“We see major calving events every 60—70 years,” Professor Fricker added.

“The calving will not directly affect sea level, because the ice shelf was already floating, much like an ice cube in a glass of water,” Australian Antarctic Program glaciologist Dr Galton-Fenzi said.

“But what will be interesting to see is how the loss of this ice will influence the ocean melting under the remaining ice shelf and the speed at which the ice flows off the continent,” he added.

The separation was detected using satellite imagery, which will be used to continue monitoring the D-28 iceberg to ensure it doesn’t pose a threat to ships.