We slowly beef up our knowledge
of the influence of ice on the surrounding ocean. At least, they are accumulations of
atmospheric dust and are acting as concentrators. This results in an inevitable release of nutrients,
including nitrogen, I am sure. The surrounding
ocean naturally responds to the increase.
The Southern Ice Sheet was at
maximal extension and is presently contracting, yet this variation is pretty
minor in terms of annual variation.
The claim it is significant in
terms of the global carbon cycle is a bit of a stretch and merely reflects the
obligatory bow to the gods of funding.
Antarctic icebergs play a previously unknown role in global carbon
cycle, climate
Image credit: NSF
(PhysOrg.com) -- In a finding that has global implications for climate
research, scientists have discovered that when icebergs cool and dilute the
seas through which they pass for days, they also raise chlorophyll levels in
the water that may in turn increase carbon dioxide absorption in the Southern
Ocean.
An interdisciplinary research team supported by the National Science
Foundation highlighted the research this month in the journal Nature
Geosciences.
The research indicates that "iceberg transport and melting have a
role in the distribution of phytoplankton in the Weddell Sea," which was
previously unsuspected, 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.
Helly was the lead author of the paper, "Cooling, Dilution and
Mixing of Ocean Water by
Free-drifting Icebergs in the Weddell Sea ,"
which was first published in the journal Deep-Sea Research Part II.
The results indicate 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
The latest findings add a new dimension to previous research by the
same team that altered the perception of icebergs as large, familiar, but
passive, elements of the Antarctic seascape. The team previously showed that
icebergs act, in effect, 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. Research also shows that these ordinary
icebergs are important features of not only marine ecosystems, but even of
global carbon cycling.
"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 NSF's Antarctic
Organisms and Ecosystems Program.
NSF manages the U.S. Antarctic Program, through which it coordinates
all U.S.
The latest findings document a persistent change in physical and
biological characteristics of surface waters after the transit of an iceberg,
which has important effects on phytoplankton populations, clearly demonstrating
"that icebergs influence oceanic surface waters and mixing to greater
extents than previously realized," said 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.
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