We slowly beef up our knowledgeof the influence of ice on the surrounding ocean. At least, they are accumulations ofatmospheric dust and are acting as concentrators. This results in an inevitable release of nutrients,including nitrogen, I am sure. The surroundingocean naturally responds to the increase.
The Southern Ice Sheet was atmaximal extension and is presently contracting, yet this variation is prettyminor in terms of annual variation.
The claim it is significant interms of the global carbon cycle is a bit of a stretch and merely reflects theobligatory bow to the gods of funding.
Antarctic icebergs play a previously unknown role in global carboncycle, climate
Image credit: NSF
(PhysOrg.com) -- In a finding that has global implications for climateresearch, scientists have discovered that when icebergs cool and dilute theseas through which they pass for days, they also raise chlorophyll levels inthe water that may in turn increase carbon dioxide absorption in the SouthernOcean.
An interdisciplinary research team supported by the National ScienceFoundation highlighted the research this month in the journal NatureGeosciences.
The research indicates that "iceberg transport and melting have arole in the distribution of phytoplankton in the Weddell Sea," which waspreviously unsuspected, said John J. Helly, director of the Laboratory forEnvironmental and EarthSciences with the San Diego Supercomputer Center at the University ofCalifornia, San Diego and Scripps Institution of Oceanography.
Helly was the lead author of the paper, "Cooling, Dilution andMixing of Ocean Water byFree-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 influencephytoplankton dynamics in an area known as "Iceberg Alley," east ofthe Antarctic Peninsula, the portion of the continent that extends northwardstoward Chile
The latest findings add a new dimension to previous research by thesame team that altered the perception of icebergs as large, familiar, butpassive, elements of the Antarctic seascape. The team previously showed thaticebergs act, in effect, as ocean "oases" of nutrients for aquaticlife and sea birds.
The teams's research indicates that ordinary icebergs are likely tobecome more prevalent in the Southern Ocean, particularly as the Antarctic Peninsula continues a well-documented warmingtrend and ice shelves disintegrate. Research also shows that these ordinaryicebergs are important features of not only marine ecosystems, but even ofglobal carbon cycling.
"These new findings amplify the team's previous discoveries abouticebergs and confirm that icebergs contribute yet another, previouslyunsuspected, dimension of physical and biological complexity to polarecosystems," said Roberta L. Marinelli, director of the NSF's AntarcticOrganisms and Ecosystems Program.
NSF manages the U.S. Antarctic Program, through which it coordinatesall U.S.
The latest findings document a persistent change in physical andbiological 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 greaterextents than previously realized," said Ronald S. Kaufmann, associateprofessor of marine science and environmental studies at the University of SanDiego and one of the authors of the paper.
The researchers studied the effects by sampling the area around a largeiceberg more than 32 kilometers (20 miles) long; the same area was surveyedagain ten days later, after the iceberg had drifted away.
After ten days, the scientists observed increased concentrations ofchlorophyll a and reduced concentrations of carbon dioxide, as compared tonearby areas without icebergs. These results are consistent with the growth ofphytoplankton and the removal of carbon dioxide from the ocean.
The new results demonstrate that icebergs provide a connection betweenthe geophysical and biological domains that directly affects the carboncycle in the Southern Ocean, Marinelli added.
In 2007, the same team published findings in thejournal Science that icebergs serve as "hotspots" for oceanlife with thriving communities of seabirds above and a web of phytoplankton, krill andfish below. At that time, the researchers reported that icebergs holdtrapped terrestrial material, which they release far out at sea as they melt, aprocess that produces a "halo effect" with significantly increasednutrients and krill out to a radius of more than three kilometers (two miles).
The new research was conducted as part of a multi-disciplinary projectthat also involved scientists from the Monterey Bay Aquarium ResearchInstitute, University of South Carolina, University of Nevada, Reno, Universityof South Carolina, Brigham Young University, and the Bigelow Laboratory forOcean Sciences.
Scripps Institution of Oceanography research biologist Maria Vernet andgraduate student Gordon Stephenson also contributed to the paper.
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