Antarctic Ice Shelf Collapse

The collapse of a huge ice shelf in Antarctica in 2002 has no precedent in the past 11,000 years, a study that points the finger at global warming says.

Measuring some 3,250 square kilometres in area and 220 metres thick, the Larsen B iceshelf broke away from the eastern Antarctic Peninsula in 2002, eventually disintegrating into giant icebergs.

Ice cores taken before the collapse contain the remains of plankton and algae embedded in layers of minerals layered over millions of years, providing clues about ice cover and climate change over the millennia.

Ice Shelf Thinned

The researchers, reporting in the British science weekly Nature, say since the end of the last Ice Age, some 11,000 years ago, the ice shelf had been intact but had slowly thinned, by several dozen meters. Its coup de grace came from a recent but decades-long rise in air temperature, they say.

"The modern collapse of the Larsen B ice shelf is a unique event within the Holocene," they write.

"The Larsen B Ice shelf eventually thinned to the point where it succumbed to the prolonged period of regional warming now affecting the entire Antarctic Peninsula region."

Balmy Weather

The Holocene is the period of relatively balmy weather that followed the last Ice Age. The research is the latest in a series of studies to sound the alarm about the effects of climate change in Antarctica, where the bulk of the world’s freshwater is locked up.

The Antarctic Peninsula, which juts northwards out of West Antarctica, is considered a warming hot-spot.

Temperatures Rising

Over the past half century, temperatures in the peninsula have risen by around two degrees Celsius.

In recent years, the peninsula has lost ice shelves totalling more than 12,500 square kilometres, equivalent to four times the area of Luxembourg.

Of the 244 glaciers that drain inland ice and feed these shelves, 87 per cent have fallen back since the mid-1950s, a British study published in April says.

For the first time ever in Glasgow, Montana, temperatures remained above zero degrees Fahrenheit (17.8C) in December. The average temperatures was 10.9 degrees Fahrenheit (6C) above normal.

All across North America, an unprecedented autumn heat wave from mid-November to early December broke or tied more than 700 daily-high temperature records from the Rockies to the East Coast. Temperatures rose into the 70F (20C) as far north as South Dakota and Maine.