"Iceberg transport and melting have a prominent role in the distribution of phytoplankton in the Weddell Sea", stated John J. Helly, the teams 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", stated John J. 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", stated Roberta L. Marinelli, director of the NSF's Antarctic Organisms and Ecosystems Programme. NSF manages the U.S. Antarctic Programme, through which it co-ordinates 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.