Plankton in polar oceans discharges benzene and toluene, two biological gases that contribute to cloud formation and impact climate, according to ICM-CSIC researchers.
The air contains trace amounts of organic gases like benzene and toluene in addition to oxygen, nitrogen, and carbon dioxide. These oxidize into small particles or aerosols, which contribute to the condensation of water in cloud droplets.
A new study from the Institut de Cièncias del Mar (ICM-CSIC), the Instituto de Química Física Rocasolano (IQFR-CSIC), and the Plymouth Marine Laboratory (PML) emphasizes the significance of clouds in understanding past and future climate changes.
If we don't get the clouds right, we won't get the climate right. We are just beginning to unveil the multiple ingredients that form cloud seeds.
Charel Wohl, Study Lead Author and Researcher, Institut de Cièncias del Mar
The study, which was published in the journal Science Advances, explains the first measurements of benzene and toluene in polar oceans and suggests that these compounds are biological in origin. Their existence in polar marine air was previously thought to be evidence of the scale of human pollution from coal and oil combustion, as well as solvent use, among others.
A Biological Origin
The only means to learn how the atmosphere was governed prior to the huge changes caused by human activity in the industrial era is to study areas where the air is still clean, like the polar regions.
To conduct the research, the group assessed benzene and toluene concentrations in surface water and air during two oceanographic campaigns, one in the Arctic and one in the Southern Ocean.
The researchers concluded that these gases were of biological origin based on their distribution, relationship to the amount of phytoplankton, and the notion that the ocean continuously released them into the atmosphere instead of capturing them from it.
The investigators then discovered that benzene and toluene released by the ocean significantly contributed to aerosol production by integrating the data into a global atmospheric chemistry and climate model.
This was particularly true in the Southern Ocean’s extremely clean and unpolluted atmosphere, where these two gases elevated the concentration of organic aerosols by 8% and up to 80% in transient situations.
According to the researchers, the natural impact of marine benzene and toluene on atmospheric chemistry was most certainly a ubiquitous and global phenomenon. However, the widespread effect of pollution would now obscure it.
Climate models will have to consider benzene and toluene emissions from the oceans if they want to get the clouds right in climate projections for both the past and the future.
Alfonso Saiz-López, Researcher, Instituto de Química Física Rocasolano
Alfonso Saiz-López headed the atmospheric modeling part of the research.
“This is another example of how millions of years of evolution have shaped the interactions between the ocean and the atmosphere, so that ocean life has not only adapted to the climate but has contributed to regulate it,” states ICM-CSIC researcher and co-author of the study Rafel Simó.
The team will continue to investigate the effect of marine microscopic life on the atmosphere in the future. In fact, they will return to Antarctic waters in just two weeks to confirm the discovery and take additional measurements.
Wohl, C., et al. (2023) Marine biogenic emissions of benzene and toluene and their contribution to secondary organic aerosols over the polar oceans. Science Advances. doi.org/10.1126/sciadv.add9031.