By Tatum Lyles Flick
Department of Chemistry Communications Specialist
Abridged version of this article published here.
Hidden in the salt spray from waves crashing on the beach are clues to our planet’s future.
Chemists at the University of Wisconsin–Madison are turning to where the ocean meets the sky to study how our past, present and future climates are affected by a complex aerosol made up of seawater, air and bits of organic matter from the organisms that call the ocean home.
The researchers are members of the Center for Aerosol Impacts on Chemistry of the Environment, or CAICE, a National Science Foundation-funded collaborative dedicated to unraveling the impact of these aerosol particles on air quality and climate.
Because the oceans cover 70 percent of the planet, it’s a daunting task.
“There’s a lot of water — a lot of ocean — and a lot of wind,” says Joseph Gord, a postdoctoral research associate, who works with CAICE.
CAICE recently received $20 million from the NSF to fund its second five years, with $3 million slated for UW–Madison. Based at the University of California, San Diego, CAICE is a collaboration between 12 universities and institutes around the country.
“To understand current climate, we need to know what happened before we were here,” says Timothy Bertram, associate director of CAICE and a professor of chemistry at UW–Madison. “We want to know what aerosol particles, central to cloud formation and the climate system, looked like in pre-industrial times.”
To investigate past conditions, CAICE scientists constructed an ocean-interface model to recreate the chemical composition of sea spray in the lab. This allows the researchers to alter conditions and simulate different geologic time periods or environmental factors. Changing ocean temperatures, an increase in ocean acidity, pollution and harmful algal blooms all alter the composition of this aerosol zone and may affect weather patterns and human health.
“We want to understand how the natural process works,” Bertram says. “We also want to understand how humans impact the oceans and the role that can have on these small particles.”
Bertram and his colleagues view creation of the simulator and their ability to evaluate the ocean system, with such high molecular diversity, as the biggest achievement of the first five-year grant from NSF.
“We measured the complexity of sea spray in the laboratory and derived a molecular mimic for it,” Bertram said. “You can make it in a beaker and you can put your hands on it, as opposed to thinking it’s too complicated to study.”
The new NSF grant moves the project forward with new purpose, focusing on three main parts: particle production; chemical reactions at the water-air interface; and how particles affect cloud formation.
UW–Madison researchers focus on chemical reactions between aerosol particles and atmospheric gases. Though the ocean is a concentrated solution of sodium chloride, the surface contains a wealth of organic material, which makes its way into sea spray and alters the composition of and reactions in that interface.
“Bacteria, phytoplankton, and viruses produce a lot of organic material, which finds itself at the interfaces,” Bertram said. “It’s really a story about a chemically complex interface, driven by the microbiology of the ocean’s surface.”
Sea spray includes numerous gases, which increases the complexity of this research. One of those gasses, dinitrogen pentoxide (N2O5), can greatly affect how much ozone is in the atmosphere. Ozone, in turn, is critical for the accuracy of climate models.
“Depending on the reactive uptake of dinitrogen pentoxide (N2O5), the concentrations of ozone and hydroxyl radical as well as the lifetime of methane can change significantly, so there’s an enormous variability,” says Gord. “Reactive uptake is basically the percent of collisions between an incoming gas molecule and an interface that lead to a chemical reaction. This molecule provides a mechanism for removing some of these nitrogen oxides (which add to ground-level ozone and particulate matter) from the atmosphere. By understanding the behavior of this molecule, we equip and enable people who study other climate processes in-depth, to make better predictions for and models of the atmosphere.”
Concentrations of nitrogen oxide molecules in the atmosphere also affect the amount of particulate matter, which, along with ozone, can take a toll on human health. Both ozone and particulate matter are monitored by the Environmental Protection Agency.
“All of this work helps us better inform the people who take all of these little pieces, build the models and make predictions,” Gord said. “An enormous number of molecules contribute to the overall picture of climate,” says Gord. “We study some of the publicly lesser-known players, to understand their behavior so people who look at the whole picture have accurate starting points for the work they do.”
The CAICE collaborators build upon a rapidly increasing collection of data and upon a shared interest and experience in chemistry and climate science.
“From a chemical perspective, we are developing methods to dissect patterns and reactions in systems that display such enormous complexity that only a center-enabled approach can succeed in understanding them,” added Gil Nathanson, co-principal investigator with CAICE and professor of chemistry at UW-Madison. “Our Center draws, not only upon chemists of all stripes, but biologists and oceanographers as well, and we connect directly with the climate modeling community. It’s a massive undertaking that leads to both fundamental and tangible discoveries, shifting the way we think about complex chemical systems in general and aerosol chemistry in particular.”
“There are many pieces of the puzzle, our lab may focus on a narrow window, but within CAICE there’s an enormous breadth of understanding and experimentation,” Gord said.
The project includes numerous experiments from a collaborative group of universities across the country, with University of Wisconsin-Madison as the second largest participant. UW-Madison’s part of the grant totals $3 million of $20 million.
Partner institutions include: University of California San Diego; Scripps Institution of Oceanography; The University of Iowa; University of Wisconsin-Madison; Colorado State University; The University of Utah; University of California Davis; The Ohio State University; Yale; University of California, Irvine; Skidmore College; and San Diego Supercomputer Center.
This work was funded by the National Science Foundation Division of Chemistry through the Center for Aerosol Impacts on Chemistry of the Environment under Grant No. CHE 1801971.