Marine plankton release about 20 million tons of sulfur into the air every year, most of which is in the form of dimethyl sulfide (DMS). In the air, it converts into sulfuric acid, which helps in cloud formation and affects the entire climate. Recent research has shown that more than a third of DMS never plays a role in cloud formation and is lost in the clouds themselves. This discovery has changed the information about the relationship between oceans and clouds. Now scientists will be better positioned to predict cloud formation.
This has been revealed by a study by the University of Wisconsin-Madison, the National Oceanic and Atmospheric Administration (NOAA), and other researchers. This investigation will have a significant impact on the knowledge of the effects of ocean life on clouds. Clouds reflect sunlight back into space and control rainfall. In this way, they greatly influence the global climate. Accurate estimates about them are significant to understand the impact of climate change.
Tim Bertram, the senior author of the study and professor of chemistry at UW Madison, suggests that the cloud formation story was actually incomplete. “For the last three to four years, we have been questioning parts of this story through laboratory experiments and large-scale field experiments. Now we can correctly connect all the stars between the formation of the oceans and the particles that make up the clouds.
UW-Madison graduate student Gordon Novak, in collaboration with 13 institutions, produced the analysis, which is published in the Proceedings of the National Academy of Sciences. A few years ago, a group at NOAA led by Patrick Veres, who collaborated on this study, discovered that DMS first converts into an HPMTF molecule in the process of making sulfuric acid that had never been identified before. In this study, the team used a NASA aircraft equipped with special instruments and detailed measurements of this chemical over the open ocean.
Bertram said that this actual DC-8 aircraft of NASA is a flying laboratory. All the seats were removed, and exact chemistry equipment was fitted so that the molecules of minimal amounts in the atmosphere and the chemical reaction between the molecules could be measured. From flight data, the team found that HPMTF very quickly dissolves in the water droplets of existing clouds and removes sulfur from the cloud’s nucleation process. Where there are no clouds, HPMTF persists and helps form new clouds by forming sulfuric acid.
Together with colleagues from Florida State University, the team pooled all these new measurements for the Global Model of Ocean Chemistry. They found that 36 percent of DMS is lost in the clouds on its way. Another 15 percent of sulfur is lost through other activities.
Less than half of the sulfur left by sea plankton comes into the atmosphere like DMS and plays its role in cloud formation. Bertram says that this sulfur reduces the rate of cloud formation.
Until recently, researchers ignored the effect of clouds on the chemical processes taking place in oceans. A significant reason for this was that it was challenging to collect the necessary data for this. But the new study reveals both the power of gathering information with the right tools and the role of clouds. It also turns out that new clouds can be formed due to the processes being affected. This research has reopened this dimension of marine chemistry.