First Direct Evidence That Human Activity Linked To Collapse Of Ice Shelf

ICE WORLD

An ice shelf is the floating extension of the grounded ice sheet. It is composed of freshwater ice that originally fell as snow, either in situ or inland and brought to the ice shelf by glaciers.

by Staff Writers
London, UK (SPX) Oct 17, 2006
The first direct evidence linking human activity to the collapse of Antarctic ice shelves is published this week in the Journal of Climate. Scientists from the British Antarctic Survey (BAS), the Centre for Polar Observation and Modelling, University College London, and the Katholieke Universiteit Leuven, (Belgium) reveal that stronger westerly winds in the northern Antarctic Peninsula, driven principally by human-induced climate change, are responsible for the marked regional summer warming that led to the retreat and collapse of the northern Larsen Ice Shelf.

Global warming and the ozone hole have changed Antarctic weather patterns such that strengthened westerly winds force warm air eastward over the natural barrier created by the Antarctic Peninsula's 2 km-high mountain chain. On days when this happens in summer temperatures in the north-east Peninsula warm by around 5 degrees C, creating the conditions that allowed the drainage of melt-water into crevasses on the Larsen Ice Shelf, a key process that led to its break-up in 2002.

Lead author Dr Gareth Marshall from the British Antarctic Survey said, "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. Climate change does not impact our planet evenly - it changes weather patterns in a complex way that takes detailed research and computer modelling 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 collapse of the 3250 km2 Larsen B Ice Shelf took place in 2002. During the past 40 years the average summer temperatures in this region of the north-east Peninsula has been 2.2C. The western Antarctic Peninsula has showed the biggest increase in temperatures (primarily in winter) observed anywhere on Earth over the past half-century.

Ice sheet - is the huge mass of ice, up to 4 km thick, that covers Antarctica's bedrock. It flows from the centre of the continent towards the coast where it feeds ice shelves.

Ice shelf - is the floating extension of the grounded ice sheet. It is composed of freshwater ice that originally fell as snow, either in situ or inland and brought to the ice shelf by glaciers. As they are already floating any disintegration (like Larsen B) will have no impact on sea level. Sea level will rise only if the ice held back by the ice shelf flows more quickly into the sea.

Loss of ice shelves near the Antarctic Peninsula is one of the most obvious signs of climate change. Elsewhere in Antarctica ice shelves are shrinking, which most scientists believe is because of a recent increase in the rate at which the ocean melts the ice.

ICE WORLD

Radar Opens New Window Into The Ice For Antarctic Scientists

London, UK (SPX) Oct 17, 2006
Scientists are getting their first glimpse into the inner secrets of an ice shelf, thanks to the innovative application of a new radar technique developed by British Antarctic Survey (BAS). Getting a clearer view of how ice behaves is important because it will help scientists predict more accurately how the ice sheet will respond to future climate change. The results are published this week in the Journal of Glaciology.

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