Antarctic Icebergs Become Floating Islands of Life

SAN DIEGO, California, June 21, 2007 (ENS) - Global climate change is causing Antarctic ice shelves to shrink and split apart, yielding thousands of free-drifting icebergs in the nearby Weddell Sea. The icebergs in the study were up to a dozen miles long and more than 120 feet high, with one extending nearly 1,000 feet into the depths.

These floating islands of ice are serving as sanctuaries for ocean life, with flocks of seabirds above and a web of phytoplankton, krill, and fish below, finds new research published in this week’s journal "Science."

The icebergs hold trapped terrestrial material, which they release far out at sea as they melt.

In satellite images, the researchers counted close to 1,000 icebergs in 4,300 square miles of ocean. The scientists estimate that icebergs are raising the biological productivity of nearly 40 percent of the Weddell Sea.

Iceberg W-86 in the Weddell Sea. Researchers found zones of abundant marine life around such icebergs.
(Photo by Rob Sherlock courtesy Scripps Institution of Oceanography)
The researchers discovered that this process produces a "halo effect" with increased amounts of phytoplankton, krill and seabirds out to a radius of more than two miles around the icebergs.

The the growing number of icebergs may also play a role in global climate change.

"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," said Smith.

To understand the icebergs’ complex impacts, the multidisciplinary team of researchers carried out the most comprehensive study ever done of individual icebergs and their immediate environment.

They took physical, biological and chemical measurements and used satellite images provided by NASA.

The wealth of data brought new challenges in how to manage this avalanche of information that were solved by researcher John Helly of the San Diego Supercomputer Center at University of California-San Diego.

"The whole is definitely greater than the sum of the parts, and to answer questions across the different areas from ecology to chemistry and climate, scientists need access to all the data," Helly said.

"And we need to reliably harvest this information at sea, thousands of miles from our shore-based labs, and to preserve it as a unique snapshot of these iceberg ecosystems at this point in history," he explained.

Helly collected the data using the SIOExplorer-in-a-Box digital library system and then stored the information in collections at the Supercomputer Center for access and analysis by scientists now and in the future.

Taken from the International Space Station, this photo shows two pieces of a massive iceberg that broke off the Ronne Ice Shelf into the Weddell Sea in October 1998. (Photo courtesy NASA)
Just getting to the icebergs was a challenge. First the scientists used satellite images to select two icebergs to study in detail.

Then they sailed aboard the Antarctic research vessel Laurence M. Gould to reach their targets in the remote Weddell Sea, an arm of the Southern Atlantic Ocean that cuts into the Antarctic continent southeast of Cape Horn.

Despite the risks of getting close to these mountains of ice – which they found can shed huge pieces or overturn without warning – the scientists began their shipboard sampling a few hundred feet from the icebergs.

They continued out to a distance of about five miles, where the icebergs’ influence was no longer detectable.

"We used a small, remotely operated vehicle, ROV, to explore the submerged sides of the icebergs and the waters between the bergs and where the ship was, standing off at a safe distance," said Bruce Robison of MBARI, an oceanographer and ROV pilot.

"We flew the ROV into underwater caves and to the undersides of the icebergs," he said, "identifying and counting animals with its color video camera, collecting samples, and surveying its topography."

These preliminary results were gathered as part of a small exploratory study funded by the National Science Foundation’s Office of Polar Programs. Many research questions remain to be answered about the role of icebergs in the pelagic ecosystem of the Southern Ocean. This research is funded to continue these studies in 2008 and 2009.

Copyright Environment News Service (ENS) 2007. All rights reserved.