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Iceberg the size of Luxembourg is cast adrift

AN iceberg the size of Luxembourg has broken off from a glacier in Antarctica.

The 2,500sq km iceberg broke off from the Mertz Glacier after being rammed by another giant iceberg, scientists said.

The collision has halved the size of the tongue that drains ice from the vast east Antarctic ice sheet.

"The calving itself hasn't been directly linked to climate change but it is related to the natural processes occurring on the ice sheet," said Rob Massom, a senior scientist at the Australian Antarctic division and the Antarctic Climate and Ecosystems Cooperative Research Centre in Tasmania.

Both organisations, along with French scientists, have been studying existing giant cracks in the ice tongue and monitored the bumper-car-like collision by the second iceberg, B-9B.

This 97km slab of ice is a remnant of an iceberg of more than 5,000sq km that broke off, or calved, in 1987, making it one of the largest icebergs ever recorded in Antarctica.

The Mertz glacier iceberg is among the largest recorded for several years. In 2002, a iceberg about 200km long broke off from Antarctica's Ross Ice Shelf. Five years later, an iceberg the size of Singapore broke off from the Pine Island Glacier in West Antarctica.

Mr Massom said the shearing off of the ice tongue and the presence of the Mertz and B-9B icebergs could affect global ocean circulation.

The area is an important zone for the creation of dense, salty water that is a key driver of global ocean circulation. This is produced in part through the rapid production of sea ice that is continually blown to the west.

"Removal of this tongue of floating ice would reduce the size of that area of open water, which would slow down the rate of salinity input into the ocean and it could slow down this rate of Antarctic bottom water formation," he said.

He said there was a risk both icebergs would become grounded on banks in the area, disrupting the creation of the dense, salty water and the amount that sinks to the bottom of the ocean.

Oceans act like a giant flywheel for the planet's climate by shifting heat around the globe via currents.