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"It was a very big surprise," says David Barnes, lead author of the study at the British Antarctic Survey, of the find of similar bryozoans 2400 kilometres apart in seas on either side of the West Antarctic ice sheet, which is 2 kilometres thick. "The most likely explanation of such similarity is that this ice sheet is much less stable than previously thought and has collapsed at some point in the recent past," he says. "And if the West Antarctic ice shelf has been lost in recent times we have to re-think the possibility of loss in future with climate change."
The bryozoans, sometimes called moss animals, are often microscopic as individuals but form colonies that can look like corals or some seaweeds. Those found were unlike others around the current coast of Antarctica.
In a brief warm period about 125,000 years ago, world sea levels were about five metres higher than today and temperatures probably at least 4°C warmer. There have been several similar warm periods in the past million years. The UN panel of climate scientists said in a 2007 report that average world temperatures could rise by between 1.1°C and 6.4°C by 2100.
The Antarctic study, in the journal Global Change Biology , says bryozoans were largely static and that their larvae, dispersed by currents, are short-lived and quickly sink. With the huge ice sheet in the way, it was hard to explain how similar colonies could be in both the seas. But if the ice were destabilised it would open a passage through which currents might, over time, carry the larvae, Barnes says.
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http://www.abc.net.au/science/articles/2010/09/01/2999453.htm
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