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Melting ice sheets create new carbon sink, say boffins

'Negative feedback' at work off Antarctica

Boffins from the British Antarctic Survey say that melting of ice shelves and glaciers in Antarctica over recent decades has allowed green plants to grow, creating a massive new carbon sink which is removing the equivalent of 12.8 megatonnes of CO2 from the seas and skies each year.

The BAS scientists say that during the last 50 years, melting ice has exposed an area of seawater the size of Wales (24,000 km2) which has now - as it now receives sunlight - got phytoplankton in it.

According to the boffins' estimates, this new population of tiny seagoing plants are dying and sinking to the seabed in huge numbers each year, taking 3.5 megatonnes of carbon with them annually - the equivalent of removing 12.8 megatonnes of CO2 from the sea and the air above it. Human-related carbon (not CO2) emissions are estimated at 8.7 billion tonnes globally, so the Antarctic sink isn't yet significant in such a context, but the BAS scientists think that it could be in future.

"This is a small amount of carbon compared to global emissions of greenhouse gases in the atmosphere but it is nevertheless an important discovery," says Professor Lloyd Peck of the BAS.

"It shows nature's ability to thrive in the face of adversity. We need to factor this natural carbon-absorption into our calculations and models to predict future climate change. So far we don't know if we will see more events like this around the rest of Antarctica's coast but it's something we'll be keeping a close eye on."

Peck calculates that the new seagoing phytoplankton populations are the second largest new phenomenon acting against climate change, with the largest being growth of new forests in the Arctic.

"Elsewhere in the world, human activity is undermining the ability of oceans and marine ecosystems to capture and store carbon," says the prof.

"At present, there is little change in ice shelves and coastal glaciers away from the Antarctic Peninsula, but if more Antarctic ice is lost as a result of climate change then these new blooms have the potential to be a significant biological sink for carbon."

Peck and his colleagues' paper, Negative feedback in the cold: ice retreat produces new carbon sinks in Antarctica is published in the journal Global Change Biology (subscription link). ®

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