Invisible scum on sea cuts CO2 exchange with air by up to 50%

30 May 2018 | Mitigation

An invisible layer of scum on the sea surface can reduce carbon dioxide exchange between the atmosphere and the oceans by up to 50%, scientists have discovered.

Researchers from Heriot-Watt, Newcastle and Exeter universities say the findings, published in the journal Nature Geoscience on Monday, have major implications for predicting our future climate.

The world’s oceans absorb around a quarter of all man-made carbon dioxide emissions, making them the largest long-term sink of carbon on Earth.

Greater sea turbulence increases gas exchange between the atmosphere and oceans and until now it was difficult to calculate the effect of “biological surfactants”.

Teams from the Natural Environment Research Council, the Leverhulme Trust and the European Space Agency developed a system that compares “the surfactant effect” between different seawaters in real time.

They found surfactants can reduce carbon dioxide exchange by up to 50%.

Dr Ryan Pereira, a Lyell research fellow at Heriot-Watt University in Edinburgh, said: “As surface temperatures rise, so too do surfactants, which is why this is such a critical finding. 

“The warmer the ocean surface gets, the more surfactants we can expect, and an even greater reduction in gas exchange.

“What we discovered at 13 sites across the Atlantic Ocean is that biological surfactants suppress the rate of gas exchange caused by the wind.”

Scientists say the surfactants are not necessarily visible like an oil slick or foam and are difficult to identify from satellites monitoring our ocean’s surface.

They say they need to be able to identify organic matter on the surface microlayer of the ocean so they can reliably estimate gas exchange rates such as carbon dioxide and methane.

Rob Upstill-Goddard, professor of marine biogeochemistry at Newcastle University, said: “These latest results build on our previous findings that, contrary to conventional wisdom, large sea surface enrichments of natural surfactants counter the effects of high winds.”

Dr Ian Ashton of the University of Exeter, who worked on the study, said: “Combining this new research with a wealth of satellite data available allows us to consider the effect of surfactants on gas exchange across the entire Atlantic Ocean, helping us to monitor carbon dioxide on a global scale.”



Source: The Guardian