Oceans emit sulfur, cooling the climate more than previously thought

Researchers have for the first time quantified global emissions of sulfur gas produced by marine life, revealing that sulfur gas is cooling the climate more than previously thought, especially in the Southern Ocean.

The study, published in the journal Science Advances, shows that the ocean not only captures and redistributes the sun’s heat, but also produces gases that create particles that instantly affect the climate. For example, clouds become brighter by reflecting this heat.

This expands the climate impact of ocean sulfur by adding methanethiol, a new compound that has not received attention until now. Researchers have only recently detected this gas, as it was previously known to be difficult to measure. Previous studies have focused on warmer oceans, but polar oceans are hot spots for emissions.

The study was led by a team of scientists from Spain’s Institute of Marine Sciences (ICM-CSIC) and Blas Cabrera Institute of Physical Chemistry (IQF-CSIC). Among them was Dr. Charel Wohl, previously at ICM-CSIC and currently at the University of East Anglia (UEA) in the United Kingdom.

Their findings represent a major advance in one of the most groundbreaking theories proposed 40 years ago about the ocean’s role in regulating Earth’s climate.

This suggests that microscopic plankton living on the ocean surface produce sulfur in the form of a gas called dimethyl sulfide, which oxidizes when it enters the atmosphere to form tiny particles called aerosols.

Aerosols reflect some of the sun’s radiation back into space, reducing the amount of heat that Earth retains. When they participate in cloud formation, their cooling effect is further increased, an effect that is opposite but on the same scale as that of well-known warming greenhouse gases such as carbon dioxide and methane.

Researchers say this new study deepens our understanding of how Earth’s climate is controlled by adding a previously overlooked element and shows the critical importance of sulfur aerosols. It is claimed that there is. They also emphasize the magnitude of human activity’s impact on the climate and that the Earth will continue to warm if nothing is done.

Dr Wall, from the UEA Center for Marine and Atmospheric Sciences and one of the lead authors, said: “This is the climatic component with the greatest cooling capacity, but also the least understood. We knew that methanethiol comes out of the ocean, but , but I didn’t know where or how much it was affecting the climate.

“Climate models have significantly overestimated the solar radiation that actually reaches the Southern Ocean. The main reason for that is that climate models don’t have the ability to accurately simulate clouds. This study partially fills a long-standing knowledge gap between models and observations.

This discovery will enable scientists to more accurately represent the climate in models used to predict warming of +1.5°C or +2°C, making a significant contribution to policymaking.

“Until now, it was thought that the ocean released sulfur into the atmosphere only in the form of dimethyl sulfide, which is primarily a plankton residue that is responsible for the pungent odor of shellfish.” said Dr. Marti Gali, a researcher at ICM. CSIC and another lead study author.

Dr Wall continued: “Today, thanks to advances in measurement technology, we know that plankton also emit methanethiol, and we have found ways to quantify on a global scale where, when and in what amounts this release occurs. The release of this compound will help us more accurately represent Southern Ocean clouds and more realistically calculate their cooling effects.”

The researchers collected all available measurements of methanethiol in seawater, added measurements taken in the Southern Ocean and the Mediterranean coast, and statistically correlated them with satellite-derived seawater temperatures. Ta.

This allowed us to conclude that methanethiol increases known ocean sulfur emissions by 25% annually and on average globally.

“It may not seem like a big deal, but methanethiol oxidizes more efficiently than dimethyl sulfide to form aerosols, so its climate impact is magnified,” IQF-CSIC co-leads say. said researcher Dr. Julián Villamayor.

The researchers also incorporated ocean emissions of methanethiol into state-of-the-art climate models to assess their impact on the Earth’s radiation balance. The effect was more pronounced in the southern hemisphere, which has more ocean and less human activity, and therefore less sulfur from burning fossil fuels.