Rising global temperatures could increase the amount of carbon dioxide naturally released by the world's oceans, fuelling further climate change, a study suggests.
Fresh insight into how the oceans can affect CO2 levels in the atmosphere shows that rising temperatures can indirectly increase the amount of the greenhouse gas emitted by the oceans.
Scientists studied a 26,000-year-old sediment core taken from the Gulf of California to find out how the ocean's ability to take up atmospheric CO2 has changed over time.
They tracked the abundance of the key elements silicon and iron in the fossils of tiny marine organisms, known as plankton, in the sediment core. Plankton absorb CO2 from the atmosphere at the ocean surface, and can lock away vast quantities of carbon.
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. 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.
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