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Antarctic Icebergs Play a Key Role in the Carbon Cycle

SDSC/SIO Researcher Leads UCSD/USD Team Studying Iceberg Movements and Melting

Published 03/28/2011

Weddell Sea iceberg showing caves formed by wave-cut ablation. Processes of ablation include melting, evaporation, and sublimation. These areas are often associated with relatively large break-ups, or calving.
Courtesy of John Helly, San Diego Supercomputer Center, UC San Diego .
A new study led by a researcher at the San Diego Supercomputer Center (SDSC) and Scripps Institution of Oceanography (SIO) at the University of California, San Diego, shows that icebergs drifting in the Antarctic's Southern Ocean play a key role in the carbon cycle process, and influence surface waters and mixing more than previously thought.

The results of the study, funded by the National Science Foundation (NSF), appear in the journal Deep-Sea Research II in a paper titled "Cooling, Dilution and Mixing of Ocean Water by Free-drifting Icebergs in the Weddell Sea." The main results from the paper were also highlighted in the March issue of Nature Geoscience.

"Iceberg transport and melting have a prominent role in the distribution of phytoplankton in the Weddell Sea," said John J. Helly, the team's lead researcher who holds joint appointments at SDSC and SIO. "These results demonstrate the importance of a multi-disciplinary scientific team in developing a meaningful picture of nature across multiple scales of measurement and the unique contributions of ship-based field research."

"The results demonstrate that icebergs influence oceanic surface waters and mixing to greater depths than previously realized," added Ronald S. Kaufmann, Associate Professor of Marine Science and Environmental Studies at the University of San Diego, and a co-author of the paper.

Specifically, the research team from UC San Diego and USD found that icebergs cool and dilute the ocean water they pass through, and also affect the distribution carbon-dioxide-absorbing phytoplankton in the Southern Ocean. The effects are likely to influence the growth of phytoplankton in the Atlantic sector of the Southern Ocean, especially in an area known as "Iceberg Alley" east of the Antarctic Peninsula.

Enhanced phytoplankton growth would increase the rate at which carbon dioxide is removed from the ocean, an important process in the carbon cycle, according to researchers.

Moreover, the findings document a persistent change in physical and biological characteristics of surface waters after the transit of an iceberg. The change in surface water properties, such as salinity, lasted at least 10 days, far longer than had been expected.

Sampling was conducted by a surface-mapping method used to survey the area around an iceberg more than 20 miles (32 kilometers) in length. The team surveyed the same area again 10 days later, after the iceberg had drifted away. After 10 days, the scientists observed increased concentrations of chlorophyll a and reduced concentrations of carbon dioxide, compared to nearby areas without icebergs.

"We were quite surprised to find the persistence of the iceberg effects over many days," said Helly, who is director of the Laboratory for Environmental and Earth Sciences at SDSC.

The new results demonstrate that icebergs provide a connection between the geophysical and biological domains that directly affects the carbon cycle in the Southern Ocean. This research significantly extends previous research results conducted in the same environment, and reveals the dynamic properties of icebergs and their effects on the ocean in unexpected ways.

"These findings confirm that icebergs are a dynamic and significant component of polar ecosystems," said Roberta L. Marinelli, director of the NSF's Antarctic Organisms and Ecosystems Program. NSF manages the U.S. Antarctic Program, through which it coordinates all U.S. research on the southernmost continent and aboard ships in the Southern Ocean.

The research was conducted as part of a multi-disciplinary project involving scientists from the Monterey Bay Aquarium Research Institute, University of South Carolina, University of Nevada, Reno, University of South Carolina, Brigham Young University, and the Bigelow Laboratory for Ocean Sciences. SIO research biologist Maria Vernet is also a co-author of the paper.

About SDSC
As an organized research unit of UC San Diego, SDSC is a national leader in creating and providing cyberinfrastructure for data-intensive research, and celebrated its 25th anniversary in late 2010 as one of the National Science Foundation's first supercomputer centers. Cyberinfrastructure refers to an accessible and integrated network of computer-based resources and expertise, focused on accelerating scientific inquiry and discovery. SDSC is a founding member of TeraGrid, the nation's largest open-access scientific discovery infrastructure.

Media Contacts:
Jan Zverina, SDSC Communications
858 534-5111 or jzverina@sdsc.edu

Warren R. Froelich, SDSC Communications
858 822-3622 or froelich@sdsc.edu

Mario Aguilera/Robert Monroe, SIO Communications
858-534-3624 or scrippsnews@ucsd.edu

Related Links

San Diego Supercomputer Center: http://www.sdsc.edu
Scripps Institution of Oceanography: http://scripps.ucsd.edu/
UC San Diego: http://www.ucsd.edu
University of San Diego: http://www.sandiego.edu/
National Science Foundation: http://www.nsf.gov/