Drifting icebergs create new ecology

Scientists see chance ocean systems could absorb carbon dioxide

June 22, 2007|By Los Angeles Times

The proliferation of drifting Antarctic icebergs caused by rising temperatures is creating a vast new ecosystem of plankton, krill and seabirds that might have the power to absorb some of the carbon dioxide that is driving global warming, scientists reported yesterday.

The researchers, led by oceanographer Kenneth Smith Jr. of the Monterey Bay Aquarium Research Institute, found that these iceberg-associated communities could cover a significant portion of Antarctic seas.

The ecosystems use photosynthesis to take carbon from the atmosphere and convert it into plant life and other forms of organic carbon that can be held in the ocean.

"I think it can be a substantial contribution" to reducing carbon dioxide levels, Smith said.

As glaciers move across Antarctica, they accumulate nutrient-rich dirt and dust. When rising temperatures cause the glaciers to break up, the resulting icebergs carry that material out to sea.

The researchers, who published their findings in the online version of the journal Science, analyzed two icebergs in the Weddell Sea, at the southernmost part of the Atlantic Ocean.

They found that soil and other organic matter escaping from the icebergs provided nutrients and support for plankton and algae. Krill then fed on the plankton.

The scientists saw more seabirds, such as Cape petrels and antarctic fulmars, near the drifting icebergs than in the open ocean.

This iceberg-influenced zone extended over two miles into the ocean surrounding the drifting ice.

Using satellite imagery, the researchers counted 962 ice islands in an area of about 4,000 square miles near their study area. Based on their data, they estimate that 39 percent of the region could contain iceberg-influenced communities.

But the significance of icebergs in global carbon dynamics remains uncertain.

"While icebergs may be important on a local scale, I seriously doubt that their impact needs to be accounted for in global carbon budgets," said Kevin Arrigo, a geophysicist at Stanford University who wasn't involved in the study.

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