Icebergs collect mini ecosystems, lock up carbon

Nifty

Icebergs, released by global warming from the icy embrace of Antarctica, have surprised scientists by playing host to many forms of life.

According to new research published in the journal Science, the bergs also act as floating carbon sinks, net accumulators of carbon dioxide.

Now drifting through the Weddell sea, the bergs are "hotspots" for ocean life thanks to trapped "terrestrial material" they have carried with them from the continent. The researchers estimate that the bergs are increasing the biological activity in as much as 40 per cent of the Weddell sea.

As the icebergs melt, they release their earthy cargo far out at sea, creating a habitable zone of up to two miles radius around each berg. In this region, phytoplankton, krill, and fish all do well below the waterline. Attracted by all this food, populations of seabirds are thriving on the icebergs, apparently using them as temporary cruise liners.

"One important consequence of the increased biological productivity is that free-floating icebergs can serve as a route for carbon dioxide drawdown and sequestration of particulate carbon as it sinks into the deep sea," said oceanographer Ken Smith of the Monterey Bay Aquarium Research Institute (MBARI), first author and principal investigator for the research.

"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," Smith added.

Smith's team carried out an astonishingly detailed and close-up study of the icebergs. They drew on satellite data from NASA to select their subjects, which they tracked in person from the research vessel Laurence M Gould. They also used a remotely operated vehicle (ROV) to explore the submerged sections of the floating ice mountains.

Bruce Robison, an oceanographer and ROV pilot said: "We flew the ROV into underwater caves and to the undersides of the icebergs, identifying and counting animals with its colour video camera, collecting samples, and surveying its topography."

Researcher John Helly, of the San Diego Supercomputer Centre (SDSC) at UC San Diego, concluded: "The whole is definitely greater than the sum of the parts." ®