6 Apr 2009

Ice shelf split a sign of global warning - scientist

8:56 am on 6 April 2009

An ice shelf the size of Hawke's Bay that is wrenching itself away from Antarctica is a symptom of global warming and will have further environmental consequences, according to a New Zealand scientist.

A satellite picture shows that a 40-kilometre-long strip of ice believed to pin the Wilkins Ice Shelf in place has snapped at its narrowest point, off the Antarctic Peninsula.

Professor Tim Naish from the Antarctic Research Centre at Victoria University says it is the ice sheets behind the ice shelf that concern him and other scientists. The ice bridge had held a vast Antarctic ice shelf in place for hundreds of years.

Professor Naish says the shelf measures about 14,000 square kilometres.

He says that as the ice shelves melt, the ice sheets start sliding faster into the ocean.

Researchers regarded the ice bridge as an important barrier to holding the remnant shelf structure in place.

Scientists say the collapse provides further evidence or rapid change in the region.

The loss of the ice bridge, which was almost 100km wide in 1950, could allow ocean currents to wash away more of the shelf.

Temperatures on the Antarctic Peninsula have risen by up to about 3 degrees Celsius in the past 50 years, the fastest rate of warming in the Southern Hemisphere.

Nine other shelves have receded or collapsed around the Antarctic Peninsula in the past 50 years.

British scientist David Vaughan, a glaciologist with the British Antarctic Survey, says the collapse of the ice shelf is the result of climate change in the region over the past 50 years.

Professor Vaughan says it is not the biggest ice shelf to collapse.

He says scientists believe warmer summers weaken ice shelves and allow them to collapse.