Surfactants slow oceanic carbon dioxide uptake

by Mary Caperton Morton
Monday, September 10, 2018

The oceans are the largest long-term carbon sink on Earth, absorbing about a quarter of all anthropogenic carbon dioxide emissions. The rate of exchange of carbon dioxide between the oceans and the atmosphere is thought to be primarily controlled by wind-driven turbulence at the sea surface. More turbulence leads to increasing gas exchange and higher rates of carbon uptake by the ocean. But in a new study, published in Nature Geoscience, scientists found that biomolecules called surfactants floating at the sea surface may significantly reduce carbon dioxide exchange with the atmosphere — reducing the uptake of carbon dioxide by up to 50 percent. “As surface temperatures rise, so too do surfactants, which is why this is such a critical finding,” said lead author Ryan Pereira of Heriot-Watt University in Scotland in a statement.

These surfactants had been previously overlooked by scientists because they are nearly invisible at the surface and difficult to identify from satellites typically used to monitor the ocean’s surface. In the new study, researchers sampled the surfactant layer at 13 sites across the Atlantic Ocean during the annual 13,500-kilometer-long Atlantic Meridional Transect cruise, led by the Plymouth Marine Laboratory and the National Oceanography Center in the United Kingdom, from the U.K. to South Africa or Chile.

“The suppression of carbon dioxide uptake across the ocean basin due to surfactants, as revealed by our work, implies slower removal of anthropogenic carbon dioxide from the atmosphere and thus has implications for predicting future global climate,” said co-author Rob Upstill-Goddard of Newcastle University in England in a statement.