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Iron a key link in ocean-climate system

‘If warming climates lower iron levels at the sea surface, as occurred in the past, this is bad news for the environment’

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The link between iron concentrations in the ocean and global temperatures may result in a feedback loop leading to yet more warming, a new study says.

FRISCO — Scientists with the University of Edinburgh say they may have pinpointed the granddaddy of all climate feedback mechanisms, saying that rising global temperatures could indirectly increase the amount of greenhouse gases released from the world’s oceans.

After studying the abundance of silicon and iron from the fossils of plankton  in a 26,000-year-old core sediment from the Gulf of California, the researchers found that, those periods when silicon was least abundant in ocean waters corresponded with relatively warm climates, low levels of atmospheric iron, and reduced CO2 uptake by the oceans’ plankton.

Plankton absorb CO2 from the atmosphere at the ocean surface, and can lock away vast quantities of carbon.

“Iron is known to be a key nutrient for plankton, but we were surprised by the many ways in which iron affects the CO2 given off by the oceans,” said study leader Dr. Laetitia Pichevin, of the University of Edinburgh’s School of GeoSciences. “If warming climates lower iron levels at the sea surface, as occurred in the past, this is bad news for the environment.”

Dr Laetitia Pichevin, of the University of Edinburgh’s School of GeoSciences, who led the study, said:

Scientists had suspected that iron might have a role in enabling plankton to absorb CO2. However, this latest study shows that a lack of iron at the ocean surface can limit the effect of other key elements in helping plankton take up carbon.

This effect is magnified in the southern ocean and equatorial Pacific and coastal areas, which are known to play a crucial role in influencing levels of CO2 in the global atmosphere.

The scientists saidtheir findings are the first to pinpoint the complex link between iron and other key marine elements involved in regulating atmospheric CO2 by the oceans.

The findings were verified with a global calculation for all oceans. The study, published in Nature Geoscience, was supported by Scottish Alliance for Geoscience Environment Society and the Natural Environment Research Council.

 

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