AN invisible layer of biological compounds sitting on the sea surface slows the rate at which the world’s oceans absorb carbon dioxide, scientists have reported.

Experts from Heriot-Watt, Newcastle and Exeter universities, who published their research in the journal Nature Geoscience, say the findings have major implications for predicting our future climate.

The oceans currently absorb around one-quarter of all carbon dioxide emissions caused by human activity, making them the largest long-term sink of carbon on Earth.

Atmosphere-ocean gas exchange is controlled by turbulence at the sea surface, the main cause of which is waves generated by wind. Greater turbulence means increased gas exchange. Until now, it was difficult to calculate the effect of biological surfactants, but the Natural Environment Research Council (NERC), Leverhulme Trust and European Space Agency-funded team developed a system that directly and in real time compares “the surfactant effect” between different sea waters collected along oceanographic cruises. Using this and satellite observations, the team 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. These natural surfactants aren’t necessarily visible like an oil slick, or a foam, and are even difficult to identify from satellites monitoring our ocean’s surface.

“We need to be able to measure and identify the organic matter on the surface microlayer of the ocean so that we can reliably estimate rates of gas exchange of climate active gases, such as carbon dioxide and methane.”