Each year, marine life feeding on plankton, such as bacteria, algae, protozoa, archaea, and others, release millions of tons of sulfur into the atmosphere, in the form of dimethyl sulfide (DMS).

In the atmosphere, this pungent-smelling compound turns into sulphuric acid, which is crucial for one of the most important parts of the Earth’s water cycle – cloud formation.

Sulfuric acid provides water droplets to a site to form into clouds. Over 70 percent of the clouds in the Earth’s atmosphere are formed over the ocean, according to NASA. Therefore, the impact of this process is immense on the Earth’s climate.

However, there are still gaps in our understanding of the process. Clouds play a crucial role in the Earth’s climate, by controlling rainfall, and reflecting solar radiation into deep space.

As the world continues to be battered by extreme weather events borne out of climate change, understanding how clouds form, and why is essential.

New research from the University of Wisconsin-Madison, The National Oceanic and Atmospheric Administration, and others, conducted using NASA’s DC-8 research aircraft has provided insights into the phenomenon, altering our understanding of how marine life influences cloud formation.

In a paper published in the journal Proceedings of the National Academy of Sciences, researchers have revealed that over one-third of the dimethyl sulfide (DMS) emitted from the ocean is absorbed by existing clouds themselves, and hence, doesn’t help new clouds form.

“It turns out that this story of cloud formation was incomplete,” said Tim Bertram, senior author of the paper and a professor of chemistry at the University of Wisconsin-Madison. “Over the last three or four years, we’ve been questioning parts of that story, both through laboratory experiments and with large-scale field experiments. Now we can better connect the dots between what’s emitted from the ocean and how you form these particulates that encourage cloud formation.”

Using NASA’s DC-8 aircraft – filled with scientific instruments – the research team captured detailed measurements of chemicals over the open sea, under both cloud conditions and the clear skies.

The data revealed that most of the dimethyl sulfide first turns into a molecule called HPMTF in the process of turning into sulphuric acid. And exiting clouds absorb HPMTF, reducing the rate of cloud formation.

Cover Image: Sam Hall/University of Wisconsin-Madison