An international research team led by scientists at the University of Exeter in the UK has determined that the world’s oceans are absorbing significantly more carbon dioxide (CO2) than previously believed. The team also included scientists from the University of the Highlands and Islands, the Herriot-Watt University (both in the UK) and the Max Planck Institute in Germany.
“Half of the carbon dioxide we emit doesn’t stay in the atmosphere but is taken up by the oceans and land vegetation ‘sinks’,” explained Exeter University Global Systems Institute Professor Andrew Watson. “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.”
The movement of CO2 between the atmosphere and oceans is known as the carbon flux. The Exeter-led team has determined that previous estimates of this flux did not take into account the differences in temperature between the surface of the ocean and the water a few metres below the surface.
“Those differences are important because carbon dioxide solubility depends very strongly on temperature,” he pointed out. “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% of global fossil fuel emissions.”
The researchers calculated carbon fluxes from 1992 to 2018. They determined that the net flux could be, at certain times and places, up to 100% greater than indicated by the uncorrected models.
“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,” highlighted Exeter University Centre for Geography and Environmental Science Dr Jamie Shutier. “That [other] 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 for CO2 now agree pretty well, which gives us added confidence in them.”