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| Photo: John Helly/SDSC |
| The exposed portion of an iceberg in the Weddell Sea rises 30 to 40 meters (98 to 131 feet) above the sea surface. Overhanging icicles result from thawing and freezing of the surface of the iceberg. |
The effects are likely to influence the growth
of phytoplankton in the Atlantic sector of the Southern Ocean and 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, said the leaders of the National Science Foundation (NSF)-funded study.
The results 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 this paper also were highlighted
in Nature Geoscience's March issue.
"Iceberg transport
and melting have a prominent role in the distribution of phytoplankton in the
Weddell Sea," said paper lead author John J. Helly, who holds joint
appointments at the San Diego Supercomputer Center and Scripps Institution of
Oceanography at UC San Diego. "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 paper
co-author Ronald S. Kaufmann, associate professor of marine science and environmental studies at the University of San Diego.
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 32 kilometers (20 miles) 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, 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. Scripps Oceanography graduate student Gordon Stephenson and research biologist Maria Vernet also are co-authors of the paper.
About
Scripps Institution of Oceanography
Scripps Institution of Oceanography at
University of California, San Diego, is one of the oldest, largest and most
important centers for global science research and education in the world. Now
in its second century of discovery, the scientific scope of the institution has
grown to include biological, physical, chemical, geological, geophysical and
atmospheric studies of the earth as a system. Hundreds of research programs
covering a wide range of scientific areas are under way today in 65 countries.
The institution has a staff of about 1,400, and annual expenditures of
approximately $170 million from federal, state and private sources. Scripps
operates robotic networks, and one of the largest U.S. academic fleets with
four oceanographic research ships and one research platform for worldwide
exploration. Birch Aquarium at Scripps serves as the interpretive center
of the institution and showcases Scripps research and a diverse array of marine
life through exhibits and programming for more than 415,000 visitors each
year. Learn more at scripps.ucsd.edu. Scripps News: scrippsnews.ucsd.edu
About UC San Diego
Fifty years ago, the
founders of the University of California, San Diego, had one criterion for the
campus: It must be distinctive. Since then, UC San Diego has achieved the
extraordinary in education, research and innovation. Sixteen Nobel laureates
have taught on campus; stellar faculty members have been awarded Fields Medals,
Pulitzer Prizes, McArthur Fellowships and many other honors. UC San
Diego — recognized as one of the top 10 public universities by U.S. News & World Report and named by
the Washington Monthly as No.1
in the nation in rankings measuring "what colleges are doing for the
country" — is widely acknowledged for its local impact, national influence and
global reach. UC San Diego is celebrating 50 years of visionaries, innovators
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