Antarctic icebergs may offset carbon emissions

A massive tabular iceberg adrift in the Weddell Sea off the Antarctic peninsula
An iceberg in the Weddell Sea off the Antarctic peninsula. Photograph: British Antarctic Survey

Icebergs that break off Antarctica and drift away are hotspots of life and may help reduce the amount of carbon dioxide in the world's atmosphere, according to new research.

American scientists said thousands of floating icebergs that had split from Antarctic shelves as a result of climate change were having a major impact on the ecology and chemistry of the ocean around them.

The icebergs hold nutrients that they release far out to sea as they melt, sustaining a community of seabirds, krill, fish and phytoplankton spread over a radius of up to two miles around each one.

University of South Carolina geochemist Timothy Shaw, one of the authors of the study, said: "The Southern Ocean lacks a major source for terrestrial material due to the absence of major rivers.

"The icebergs constitute a moving estuary, distributing terrestrial-derived nutrients that are typically supplied by rivers in other areas of the oceans."

The phytoplankton sustained by the icebergs absorbs CO2 from the water around it, the study said. This could have important implications for climate change research, as it may mean the world's oceans will be able to absorb more CO2 from the atmosphere than previously thought.

The researchers counted 1,000 icebergs in satellite images of 4,300 square miles of the Southern Ocean's Weddell Sea, a huge stretch of water that cuts into the Antarctic continent south-east of Cape Horn. Based on their new understanding, they estimate icebergs are raising the biological productivity of nearly 40% of the Weddell Sea's area.

Ken Smith, an oceanographer at the Monterey Bay Aquarium Research Institute (MBARI) and the leader of the research, said: "While the melting of Antarctic ice shelves is contributing to rising sea levels and other climate change dynamics in complex ways, this additional role of removing carbon from the atmosphere may have implications for global climate models that need to be further studied."

The study, which is published in this week's edition of the journal Science, focussed on two icebergs of up to 13 miles across and 40 metres high, one of which extended 300 metres under water.

The scientists used a small, remotely operated vehicle (ROV) to explore the submerged sides of the icebergs and the waters between them and the ship.

The ROV, which was fitted with a colour video camera, was sent into underwater caves and to the undersides of the icebergs, allowing the researchers to identify and count animals, and collect samples.

The scientists plan to follow up their work with more studies over the next two years.