Bubble Chemistry at the Ocean-Atmosphere Boundary
When tiny sea organisms called phytoplankton die, they produce oils, proteins, and other molecules that tend to stick to ocean water bubbles. Rising to the surface, these bubbles break and form sea spray. The remains of the organisms are lofted into the air where the carbon they contain can influence the chemical makeup of the atmosphere. In a new paper published in the journal Environmental Research Letters, a multi-institutional team of researchers including scientists at Pacific Northwest National Laboratory described a method to understand which types of these carbon-containing materials are prevalent in different parts of the ocean. They also determined how likely these materials are to stick to ocean bubbles that ultimately affect the chemical composition of the ocean surface and subsequent sea spray.
The team included scientists at Los Alamos National Laboratory, University of Alaska, Harvard University, New Mexico Institute of Mining and Technology and University of California San Diego.
The researchers reviewed relevant literature to collect measurements of organic material chemical properties. Their reviews covered a broad range of publications, including studies in food science and other applied fields. They also gathered information about the concentrations of various types of organic compounds in different parts of the ocean. By applying basic physical chemistry concepts, they investigated how classes of organic molecules similar to those found in different parts of the ocean stick to sea spray surfaces, thus influencing their chemistry.
Covering more than 70 percent of the Earth’s surface, the ocean plays a key role in regulating climate, in part because the spray from ocean waves act as seeds for the formation of cloud droplets. Cloud droplets that form from sea spray also help shade the planet from some of the sun’s rays by reflecting sunlight back to space. Understanding the chemistry that makes up these droplets and why it changes is important to knowing how the climate will react. This understanding also helps improve how natural aerosol particles like sea spray are represented in global climate models that predict how the climate will change over time.
Just as the continents have diverse ecosystems, such as forests, grasslands, and deserts, oceans also have different ecosystems that depend on factors such as ocean currents, sunlight, temperature and available nutrients. Variations in ocean chemistry can affect organic enrichment of sea spray particles, which in turn affects the chemistry of naturally-occurring atmospheric particles. A team of researchers, including a Department of Energy scientist at Pacific Northwest National Laboratory, devised a method to determine which types of compounds are prevalent in different ocean ecosystems, and how these compounds affect the chemical composition of the ocean surface water and the associated sea spray. The team collected descriptions and concentration information of organic chemical properties from a broad range of publications, including studies in food science and other applied fields. By applying basic physical chemistry relationships, they investigated how likely classes of organic molecules similar to those found different ocean ecosystems are to stick to bubble surfaces. Using a newly developed method for linking the output of ocean biogeochemistry models to the chemical composition of aerosols, the findings suggest that macromolecular distributions and surface activity should be considered in future marine systems simulations and may bring insight into Earth system models.
The U.S. Department of Energy’s Office of Science, Biological and Environmental Research funded this project via the Scientific Discovery through Advanced Computing and the Earth System Modeling Programs, with additional support from the National Science Foundation.