If you’ve ever walked along the shore and inhaled deeply, you’ve probably sensed it. Sea spray contains far more than water. As the briny, earthy aroma indicates, the tiny aerosol droplets also carry salts as well as organic compounds. And, as it turns out, these additional molecules have a profound impact on the earth’s climate.
As water evaporates at the surface of the sea, it rises to form clouds. Wave action creates aerosols—microscopic airborne particles trapped in water droplets. These aerosols influence the formation and physical properties of clouds, such as their ability to absorb sunlight or trap heat.
Climatologists explain that, depending on their chemical makeup, different aerosols scatter or absorb sunlight to varying degrees. In fact, according to NASA, an aerosol’s effect on light depends primarily on the composition and color of the particles. In general, “bright-colored or translucent particles tend to reflect radiation in all directions and back towards space. Darker aerosols can absorb significant amounts of light.”
Salt particles, sulfates, and nitrates therefore tend to be more reflective and have a cooling effect on the atmosphere, according to a recent study, whereas black carbon absorbs radiation, warming the atmosphere. Organic carbon, sometimes called brown carbon or organic matter, can also have a warming influence on the atmosphere, depending on the brightness of the underlying ground.
“Sea spray aerosol was thought for a long time to be just salt—sodium chloride—and that’s not true,” Vicki Grassian a distinguished professor in the departments of Chemistry and Biochemistry, Nanoengineering, and the Scripps Institution of Oceanography at UC San Diego told Ensia. “There’s a lot more that comes out of the water—viruses, bacteria, organic compounds, parts of cell walls—little ‘bio bits,’ if you will.” Scientists believe that understanding these aerosols and their chemical compositions is critical to understanding cloud formation and fluctuations in the Earth’s climate.
Cloud formation has been extremely difficult to capture in mathematical formulas in the past. Part of the difficulty can be attributed to the fact that traditional calculations have been completed using principles governing pure water molecules. Aerosol studies such as Grassain’s have demonstrated that, in order to be mathematically precise, cloud formation formulas will need to be adjusted to accommodate different molecular compositions. Scientists are hopeful that understanding these variables will help make future weather models increasingly accurate.
I find it exhilarating to reflect on the fact that such a tiny unit of water—an aerosol—can impact the global environment. What are your thoughts? Do you think that aerosol studies may enrich our understanding of the Earth’s climate?
