Melting bergs may play a role in global carbon cycle
By Summit Voice
SUMMIT COUNTY —As icebergs melt, they dilute and cool surrounding water, raising chlorophyll levels that may, in turn, increase carbon dioxide absorption in the Southern Ocean, according to a research team funded by the National Science Foundation.
The new research has global implications for climate research, showing that icebergs are especially likely to influence phytoplankton dynamics in an area known as “Iceberg Alley,” east of the Antarctic Peninsula, the portion of the continent that extends northwards toward Chile.
“Iceberg transport and melting have a role in the distribution of phytoplankton in the Weddell Sea,” said John J. Helly, director of the Laboratory for Environmental and Earth Sciences with the San Diego Supercomputer Center at the University of California, San Diego and Scripps Institution of Oceanography.
That role was previously unsuspected, Helly said. The research may shift the perception of icebergs. Instead of just being passive elements in the Antarctic seascape, the bergs act as ocean “oases” of nutrients for aquatic life and sea birds.
The teams’s research indicates that ordinary icebergs are likely to become more prevalent in the Southern Ocean, particularly as the Antarctic Peninsula continues a well-documented warming trend and ice shelves disintegrate.
“These new findings amplify the team’s previous discoveries about icebergs and confirm that icebergs contribute yet another, previously unsuspected, dimension of physical and biological complexity to polar ecosystems,” said Roberta L. Marinelli, director of the National Science Foundation’s Antarctic Organisms and Ecosystems Program.
The latest findings document a persistent change in physical and biological characteristics of surface waters after the transit of an iceberg. The changes have important effects on phytoplankton populations, clearly demonstrating “that icebergs influence oceanic surface waters and mixing to greater extents than previously realized,” according to Ronald S. Kaufmann, associate professor of marine science and environmental studies at the University of San Diego and one of the authors of the paper.
The researchers studied the effects by sampling the area around a large iceberg more than 32 kilometers (20 miles) long; the same area was surveyed again ten days later, after the iceberg had drifted away. After ten days, the scientists observed increased concentrations of chlorophyll a and reduced concentrations of carbon dioxide, as compared to nearby areas without icebergs. These results are consistent with the growth of phytoplankton and the removal of carbon dioxide from the ocean.
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, Marinelli added.
In 2007, the same team published findings in the journal Science that icebergs serve as “hotspots” for ocean life with thriving communities of seabirds above and a web of phytoplankton, krill and fish below. At that time, the researchers reported that icebergs hold trapped terrestrial material, which they release far out at sea as they melt, a process that produces a “halo effect” with significantly increased nutrients and krill out to a radius of more than three kilometers (two miles).
The new research was conducted as part of a multi-disciplinary project that also involved 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.
Scripps Institution of Oceanography research biologist Maria Vernet and graduate student Gordon Stephenson also contributed to the paper.
Filed under: climate and weather, Environment, global warming, Marine biology Tagged: | Antarctic Peninsula, Environment, global warming, icebergs, National Science Foundation, phytoplankton, Scripps Institution of Oceanography, Southern Ocean, Summit County News