Scientists have discovered that an invisible layer of biological compounds on the sea’s surface can reduce carbon dioxide exchange — the process by which the gas moves between the atmosphere and the oceans — by as much as 50 per cent.
The researchers from Exeter, Heriot-Watt and Newcastle universities say their findings have major implications for predicting the planet’s future climate.
The world's oceans currently absorb around a quarter of all anthropogenic carbon dioxide emissions, making them the largest long-term sink of carbon on Earth. Atmosphere-ocean gas exchange is driven by turbulence at the sea surface, which is primarily caused by wind-generated waves.
Greater turbulence leads to increased gas exchange — but until now it has been difficult to calculate the effect of biological surfactants on the exchange. The team developed a novel experimental system to compare the so-called “surfactant effect” between different sea waters collected by survey vessels in real time.
At 13 sites across the Atlantic Ocean, the team discovered that biological surfactants suppress the rate of gas exchange caused by the wind. The results build on previous findings that, contrary to conventional wisdom, large sea surface enrichments of the invisible slime counter the effects of high winds.
The scientists made unique measurements of gas transfer using a purpose-built tank that could quantify the relative exchange of gases impacted only by surfactants present at these sites.
"As surface temperatures rise, so too do surfactants, which is why this is such a critical finding,” explains Dr Ryan Pereira of Heriot-Watt University. “The warmer the ocean surface gets, the more surfactants we can expect, and an even greater reduction in gas exchange.”
The suppression of CO2 uptake across the ocean due to surfactants implies the slower removal of human-generated CO2 from the atmosphere. Therefore, the findings will have an impact on predicting the future climate.