How iron cycles can give new insight into the effects of climate change

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Researchers found that deep winter mixing plays the most important role in transporting iron to the surface in the Southern Ocean

Philip Boyd and his colleagues at the University of Liverpool published an article about iron cycles in a journal called Nature Geoscience.  The study suggested that some aspects of iron cycling in the Southern Ocean could inform researchers about the effects of climate change.

Boyd and his international team of scientists were able to analyze existing data on the Southern Ocean along with satellite imagery, to quantify the iron levels supplied to the surface waters of the Southern Ocean.  The data suggests that deep winter mixing, which carries colder, nutrient-rich water from the depths of the ocean to the surface, plays a vital role in transporting iron.  The iron is important because it is able to stimulate the development of phytoplankton, which is a key component to the ocean’s carbon cycle and food chain.

Using information on the vertical distribution of iron from the top 1,000 m of southern ocean, researchers found that deep water mixing supplies ten times more iron than through the year-round diffusion across density surfaces (called diapycnal diffusion).

These findings are important because the iron limits biological productivity, as well as air to sea carbon dioxide exchange.  These unique characteristics of iron make it distinct among other nutrients.  The Southern Ocean’s nutrient supply is affected by changes in the climate, such as winds and freshwater input, differently than other oceans in the world.   Also, the Southern Ocean, which is located in the southernmost waters that surround Antarctica, influences the global ocean system via northward flowing currents.  Scientists have known for a while that this ocean is crucial in the uptake of atmospheric carbon dioxide, and now they are able to use iron cycling data to predict changes in the global climate.

 

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Journal Reference:

  1. Alessandro Tagliabue, Jean-Baptiste Sallée, Andrew R. Bowie, Marina Lévy, Sebastiaan Swart, Philip W. Boyd. Surface-water iron supplies in the Southern Ocean sustained by deep winter mixingNature Geoscience, 2014; DOI:10.1038/ngeo2101

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