Global Warming Linked to Antarctic Ice Shelf Collapse

British and Belgian scientists have found evidence that man made global warming and thinning of the ozone layer over Antarctica have strengthened western winds blowing around Antarctica and have brought warm air from the middle latitudes to the northern Antarctic Peninsula. This fact was responsible for the retreat and collapse of the northern Larsen Ice Shelf collapse in 2002. "This is the first time that anyone has been able to demonstrate a physical process directly linking the break-up of the Larsen Ice Shelf to human activity," said Gareth Marshall from the British Antarctic Survey.

"Climate change does not impact our planet evenly - it changes weather patterns in a complex way that takes detailed research and computer modeling techniques to unravel. What we've observed at one of the planet's more remote regions is a regional amplifying mechanism that led to the dramatic climate change we see over the Antarctic Peninsula."

The ice shelf that collapsed into the Weddell Sea was 3250sqkm (1,255 sq-mile), bigger than Luxembourg.

The Antarctic Peninsula's mountains - about 2000m high - protected the Larsen ice shelf on its eastern side from the warmer winds. "If the westerlies strengthen the number of times that the warm air gets over the mountain barrier increases quite dramatically," said John King from the British Antarctic Survey.

Temperatures measured during the past 40 years in the north-east Antarctic Peninsula showed a summer average of 2.2degC (36 degree Fahrenheit). The biggest increase in temperatures (primarily in winter) anywhere on Earth over the past half-century was measured in the western Antarctic Peninsula.

The westerly winds, when they pass above these mountains, can raise the temperature to 5.5degC (45 degrees Fahrenheit) and on the peak days even to about 10degC. These temperatures melted the ice, drained the melt-water into the crevasses of the ice shelf, and eventually broke it apart. Analyses of the sediments on the seabed revealed that Larsen Ice Shelf had been in place for 5000 years. "Further south on the main Antarctic continent temperatures are pretty stable," King said.

"There is no clear direct evidence of human activity affecting the main area."

But Dr Chris Rapley, the director of the British Antarctic Survey, warns that the warming trend is dangerous for the future. "Ultimately, yes, I think that's bound to be the case... We've seen this southward migration as the wave of increased temperatures has penetrated further and further south."

The ice sheet is the ice layer - up to 4 km high - that wraps Antarctica's bedrock. It slowly glides from the interior of the continent towards the coast where it maintains ice shelves. An ice shelf is the floating extension of the grounded ice sheet. As ice shelves (like Larsen B) are already floating, any disintegration won't provoke devastating waves.

But their total melting could have an impact on sea level, raising it, but this would be insignificant, due to the small percentage stocked by the ice shelves. But the removal of the ice shelves could accelerate the gliding of land glaciers toward the sea, at least on the short term. And the melting of this ice could raise sea levels.

Recently, two major glaciers in eastern Antarctica were revealed to have started discharging ice into the sea. All around Antarctica ice shelves are losing volume, a sign of the increase in the speed at which the ocean melts the ice.