Oceans are often seen as mere water reservoirs regulating the climate. However, they hide a previously unsuspected chemical role. An international team has measured for the first time a sulfur-containing gas, methanethiol, produced by marine life. A discovery that shifts our understanding of the interaction between ocean and atmosphere.
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By analyzing the emissions of this gas, the researchers found that it contributes to cooling the Earth's atmosphere, particularly above the Southern Ocean. This cooling, more significant than previously thought, relies on mechanisms that had long remained beyond the reach of scientific instruments.
Methanethiol is produced by microscopic organisms, such as plankton, living near the surface. Once released into the atmosphere, it undergoes oxidation and forms aerosols. These tiny particles reflect sunlight, thereby helping to reduce the heat retained by the Earth. They also play a key role in cloud formation.
This research, published in
Science Advances, was led by Spanish scientists from ICM-CSIC and IQF-CSIC, in collaboration with the University of East Anglia. It reveals that methanethiol increases the known sulfur emissions from oceans by 25%, a significant boost for climate models.
This breakthrough relies on recently improved measurement techniques. By combining data obtained in laboratories, in the field, and via satellites, the researchers were able to map global methanethiol emissions. They also showed that polar regions, often overlooked, are hotspots for these emissions.
The climatic impact of methanethiol is particularly pronounced in the Southern Hemisphere, where anthropogenic sulfur emissions are lower. Climate models incorporating this data show improved representation of clouds and their cooling effect.
According to the researchers, this discovery helps fill a critical gap between observations and climate models. Until now, the latter underestimated the reflection of sunlight over the Southern Ocean, a key region for the planet's energy balance.
The team emphasizes that this research highlights the importance of interactions between marine biology and the climate. It also underscores the complexity of the climatic balance, particularly in a warming world.