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Study Finds Significantly Higher Net Flux of Carbon in Oceans

According to a new study, the world’s oceans absorb more carbon compared to the amounts proposed by a majority of the scientific models.

Image Credit: Don Pablo/

Earlier predictions of the movement of carbon (called “flux”) between the oceans and atmosphere have not taken into account differences in temperature at the surface of the water and a few meters below.

Headed by the University of Exeter, the new study has considered this and found a considerably higher net flux of carbon into the oceans.

It estimates CO2 fluxes from 1992 to 2018, determining up to twice as much net flux in specific times and locations than unadjusted models.

Half of the carbon dioxide we emit doesn’t stay in the atmosphere but is taken up by the oceans and land vegetation ‘sinks’. Researchers have assembled a large database of near-surface carbon dioxide measurements—the ‘Surface Ocean Carbon Atlas’—that can be used to calculate the flux of CO2 from the atmosphere into the ocean.

Andrew Watson, Professor, Global Systems Institute, University of Exeter

Watson continued, “Previous studies that have done this have, however, ignored small temperature differences between the surface of the ocean and the depth of a few metres where the measurements are made. Those differences are important because carbon dioxide solubility depends very strongly on temperature.”

We used satellite data to correct for these temperature differences, and when we do that it makes a big difference-we get a substantially larger flux going into the ocean. The difference in ocean uptake we calculate amounts to about 10 per cent of global fossil fuel emissions.

Andrew Watson, Professor, Global Systems Institute, University of Exeter

According to Dr Jamie Shutler, from the Centre for Geography and Environmental Science in Exeter’s Penryn Campus at Cornwall, “Our revised estimate agrees much better than previously with an independent method of calculating how much carbon dioxide is being taken up by the ocean.”

That method makes use of a global ocean survey by research ships over decades, to calculate how the inventory of carbon in the ocean has increased. These two ‘big data’ estimates of the ocean sink for CO2 now agree pretty well, which gives us added confidence in them.

Dr Jamie Shutler, Centre for Geography and Environmental Science, University of Exeter

The study authors include researchers from Herriot-Watt University, the University of the Highlands and Islands, as well as from the Max Planck Institute in Germany.

The study was financially supported by the Royal Society, the Natural Environment Research Council, and the European Space Agency.

Journal Reference:

Watson, A. J., et al. (2020) Revised estimates of ocean-atmosphere CO2 flux are consistent with ocean carbon inventory. Nature Communications.


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