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ENVIRONMENT: Melting Ice Offers Window on Polar Ecosystem

Stephen Leahy

BROOKLIN, Canada, Feb 27 2007 (IPS) - The collapse of Antarctic ice shelves due to climate change is providing the first views of marine life hidden deep under the polar ice for more than 5,000 years.

A 10-week Antarctic international expedition to probe the region’s secrets is also the first major scientific effort of the International Polar Year that was officially launched Monday in Paris and London.

The massive ice shelves that fringe the southern continent are hundreds of kilometres in size and a kilometre thick but floating above the sea floor. And strange forms of life survive in the dark, icy depths, previously only glimpsed by scientists through holes drilled through the ice.

“There are all kinds of new life no one has seen before,” said Ron O’Dor, chief scientist of the Census of Marine Life, which organised this and 12 other expeditions as part of its Census of Antarctic Marine Life project.

Warming temperatures led to the collapse of the Larsen A and B ice shelves, 12 and five years ago, respectively, exposing a 10,000-sq km portion of the Antarctic seabed for the first time in at least 5,000 years and possibly 12,000 years.

More than 50 scientists from 14 countries spent the last 10 weeks aboard Germany’s Alfred Wegener Institute’s research icebreaker Polarstern investigating what may be the most untouched region of the Earth.

“The collapse of the Larsen shelves may tell us about impacts of climate-induced changes on marine biodiversity and the functioning of the ecosystem,” said Julian Gutt, a marine ecologist with the Alfred Wegener Institute for Polar and Marine Research and chief scientist on the Polarstern expedition.

“We were in the unique position to sample wherever we wanted in a marine ecosystem considered one of the least disturbed by humankind anywhere on the planet,” Gutt said in a statement.

Climate change is having a considerable impact on both the Antarctic and Arctic polar regions. It is both the reason for and the central theme of the International Polar Year (IPY), a 1.7-billion-dollar scientific effort over two years by 50,000 scientists and researchers from more than 60 nations.

What happens in the polar regions matters to everyone because they are the drivers of much of planet’s weather. Climate change is changing conditions there more quickly than anywhere else.

“The change of phase from snow and ice to water is the biggest tipping point in the Earth’s system,” Chris Rapley, director of the British Antarctic Survey, said in a video message from Antarctica.

“So, over the next two years, I’m looking forward to major progress on key issues, such as ‘How are the ice sheets responding?’ and indeed the trillion-dollar question from the point of view of sea-level rise, ‘How much, how quickly?”

The Larsen ice shelves that collapsed are in the Antarctic Peninsula, which has warmed four times faster than rest of the planet over the past 50 years. Scientists on the Polarstern expedition used underwater remotely-operated vehicles equipped with cameras and sampling devices as well as special trawling equipment to explore and obtain samples to find out how marine life is responding to the changes.

“We found a surprising mix of deep sea creatures and colonisers,” said Gauthier Chapelle, a biologist at the Brussels-based International Polar Foundation.

Deep sea species such as sea lilies (members of a group called crinoids) and their relatives, sea cucumbers and sea urchins were found in the shallow, newly exposed sea bottom. Such species are adapted to living in the deep sea where there is no light and little food, Chapelle told IPS.

Few species can endure such conditions, and scientists estimate that perhaps there is one percent of animal abundance compared to sea beds in the open areas of the Weddell Sea.

Meanwhile new species – colonisers – are beginning to move in, such as gelatinous sea squirts and octopus.

“The diversity and abundance of celaphods (octopus species) was remarkable,” said Elaina Jorgensen, a fisheries biologist with the National Oceanic and Atmospheric Administration in Seattle, Washington.

“The video shows they were burrowing into the sea bottom rather than living under rocks like they do elsewhere,” Jorgenson told IPS.

In addition, at least 15 new-to-science species of shrimp-like creatures have been tentatively identified, although detailed analysis still needs to be done. Scientists also discovered large numbers of krill, another shrimp-like creature, which has attracted fish and whales into the area.

“Four Arnoux’s Beaked Whales were spotted and that’s big news because they are rare,” Jorgenson said. Arnoux’s Beaked Whale is a 10-metre-long whale with a protruding lower jaw that is found only in the Southern Ocean.

Large numbers of Minke whales, a smaller and more numerous species, have also moved into the area.

But this upsurge of new life may be temporary. An important planktonic algae grows underneath sea ice that is the main food source for krill, in turn a food source for most large species in the Southern Ocean. An adult blue whale alone eats about four million individual krill per day.

Less ice means less algae, and perhaps fewer krill, which would have a major impact in the region.

“Predicting the future of higher levels in the food chain, e.g. animals living at the sea-floor or fish, is very difficult,” Gutt said.

However, it is clear that in the “Larsen zone a major biodiversity shift will happen and the unique under-ice shelf system will disappear.”

The underwater drama taking place beneath the former ice shelves is a competition between species that thrive under difficult conditions and others that are moving in now that sunlight is reaching the water and allowing phytoplankton – the base of the marine food web – to grow.

“This is virgin geography,” said Chapelle. “If we don’t find out what this area is like now following the collapse of the ice shelf, and what species are there, we won’t have any basis to know in 20 years’ time what has changed, and how global warming has altered the marine ecosystem.”