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Week 48/2009: Hope for the ice shelves of Antarctica

It has been general knowledge for some time that a layer of meltwater is hiding within the depths of the Antarctica glacier.

The half-metre thick layer extends to an area of 60,000 square kilometres. A recent doctoral dissertation shows that the water layer freezes in winter.

Kai Rasmus, who defended his doctoral thesis in geophysics, calculated the freezing with a model he developed. He also tested what the model forecasts should global warming be 1.5 Celsius in 50 years, which may well happen. The freezing of the water was delayed, but it still had time to freeze over during the winter. This is just as well because if the water did not freeze over, this water layer, located only about twenty centimetres below the surface, would eventually reach the surface of the ice.

“This could accelerate the breakdown of the continental glacier’s ice shelves,” says Rasmus.

Ice shelves are masses of ice which extend out to the sea and are attached to an ice cap. It is believed that the shearing of ice shelves results from global warming.
The calculations by Rasmus also give hope that the meltwater layer will continue to freeze over in the future. However, the models are not totally accurate in their forecasting, since glaciers may behave in very unpredictable ways.

“Surprises are possible. Ten years ago the models predicted that glaciers, due to their heavy mass, would be expected to react very slowly to global warming, within a time scale of 10,000 years. A few years ago it had decreased to only hundreds of years, and now it is decades.

In his doctoral dissertation, Rasmus also studied the behaviour of light in Antarctica’s snow, ice and sea areas. For investigating the optical characteristics of snow, he came up with a new measuring method with which the behaviour of light can now be studied without breaking the surface of the snow.
Due to the high reflectivity of its snow cover, Antarctica is an important factor in the global climate system.

Text: Tapio Ollikainen

Photo: Wikipedia.org

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