CANBERRA • An iceberg the size of urban Sydney has broken away from east Antarctica, but not because of climate change, the Australian Antarctic Division (AAD) said yesterday.

The 1,636-sq km table iceberg "calved" from the Amery Ice Shelf, the third-largest on the ice continent, located between Australia's Davis and Mawson research stations, on Sept 26.

The iceberg, officially called D-28, separated from the front of the ice shelf, which scientists had been monitoring closely since the early 2000s, according to AAD, an Australian government agency.

It had already been predicted that a large iceberg would break off between 2010 and 2015.

"We don't think this event is linked to climate change," said Professor Helen Amanda Fricker at the US-based Scripps Institution of Oceanography. "It's part of the ice shelf's normal cycle, where we see major calving events every 60-70 years."

The last major calving event on the Amery Ice Shelf, which has an estimated floating ice area of 60,000 sq km, was in 1963-64.

"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," Prof Fricker said.

Ice shelves are floating platforms of ice attached to coastlines.

Dr Ben Galton-Fenzi, a glaciologist with AAD, said the fracture will not directly affect sea levels.

"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 said.

DPA