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Erratic boulders indicate past antarctic ice sheet behaviour

By Tamara Croes - 03 Apr 2011 13:11:0 GMT
Erratic boulders indicate past antarctic ice sheet behaviour

A recent study carried out by the Aberystwyth and Leeds Universities indicates that the Antarctic Ice Sheet has covered James Ross Island several times in the past and retreated again. The Antarctic Ice Sheet contains about 90% of the world's ice and is therefore of supreme importance to geoscientists trying to predict climate change. According to NASA the sea level would rise to 197 feet or about 60 meters if all the ice in it would melt.

Since there is controversy over the subject of climate change, it is important to study the behaviour of ice sheets in the past, in order to predict what may happen in the futureThe study focused on ''erratic'' rocks, which are rocks that differ totally from the local sedimentary rocks and have been transported there by moving ice.

On James Ross Island the team found granite boulders, some as big as three meters across, which are obviously totally different from the local volcanic rock.  The team then studied the composition of the granite boulders and discovered that they were identical to the Antarctic Peninsula rock. The surprise in this is that the Antarctic Ice Sheet may at times in the past 25000 years have been large enough to extend all the way across to James Ross Island.

Aberystwyth University Professor Neil Glasser, the team leader, said that the team was surprised by the size and amount of the boulders. The team surveyed a part of James Ross Island called Ulu Peninsula, where they closely studied an area of around 600 square km, mapped the distribution of the erratics and took samples.

A recently developed technology called cosmogenic exposure age dating is now being used at Aberystwyth University to determine the length of time the granite boulders were exposed to the sun, giving scientists important information about when the possible expansion and retraction of the giant ice sheet took place. This could help predict the behaviour of the ice sheet in the future. Scientists are particularly interested in periods in the past in which CO2 levels were at levels comparable to now.

The Natural Environment Research Council (NERC) funded the research project and British Antarctic Survey (BAS), which is part of the NERC, organized the fieldwork and assisted the project physically.