Blooming Southern Ocean's role in climate change
10 October 2000
University of East Anglia and Plymouth Marine Laboratory Joint News Release
Scientists from the University of East Anglia, Norwich, and Plymouth Marine Laboratory have solved a long-debated problem - and confirmed the vital influence of the polar waters of the Southern Ocean on the earth's climate.
The new research, which confirms that adding iron stimulates growth
of microscopic algae in the cold Antarctic waters, was co-funded by
the UK Natural Environment Research Council (NERC) and New Zealand's
National Institute of Water and Atmospheric Research, and is published
in the science journal Nature on October 12.
Dr. Cliff Law of Plymouth Marine Laboratory, said, "Our previous work has shown that iron is important in other regions, but the big challenge was proving it in the Southern Ocean."
Three and a half tonnes of dissolved iron were added to a 50 square kilometre patch of water. The bloom of microscopic algae that followed caused a reduction of 10% in dissolved carbon dioxide during the two weeks, in the process taking up about 1000 tonnes of carbon and resulting in an increased uptake of the greenhouse gas from the atmosphere.
Scientists believe that the unique circulation of the Southern Ocean makes it the main ocean region that influences the atmospheric concentration of carbon dioxide.
Professor Andrew Watson, from the University of East Anglia, said, "The changes we saw after adding the iron may well explain past changes in the Earth's carbon dioxide levels - during and at the end of the Ice Ages. It is evident that this is a driver for climate change. We know that there was a far higher flux of iron in the atmospheric dust to the oceans in glacial times. Our study indicates this was responsible for about half of the big change in atmospheric carbon dioxide that occurred then."
But he warned that this was not a signal to engineer climate change. "Iron fertilization could contribute in a modest way to the reduction of carbon dioxide, but reducing emissions has greater potential and should be the first line of approach. Iron fertilization on a large scale would have implications for the planet's ecosystems that would need careful consideration. There are ethical issues too; the oceans are a common heritage of humankind, so who decides which country or corporation should be allowed to use them to offset their carbon dioxide emissions?"
Dr Law reinforced this view. "We cannot predict how the marine ecosystem would respond so large-scale iron fertilization would be inadvisable."
When the scientists left after 13 days, the bloom was still going
strong, and they were surprised to find it in remarkable satellite
images of the region six weeks later.
Dr. Law said "Its very cloudy over the Southern Ocean at this time of year and clear satellite images are rare. So it was quite a shock to see a green filament about 150 kilometres long near our experimental site."
The bloom faded over the following weeks, but its appearance as a long filament has confirmed ideas of how the ocean mixes. Dr Law said "The stirring motion stretched the bloom into a circular filament, just as happens with a drop of cream in your coffee".
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1. Plymouth Marine Laboratory is part of the Natural Environment Research Council (NERC). NERC leads in the UK in providing independent research and training in the environmental sciences.
2. The University of East Anglia's School of Environmental Sciences produces internationally important research across the full spectrum of the environmental sciences, including climate change and oceanography.
Press release: 20/00
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