by Maritte O’Gallagher
The Arctic regions that surround the North Pole are warming two to four times faster than the rest of the world, causing dramatic changes to polar environments and ecosystems. Scientists study clouds because they play an important, often complex role in modulating the Arctic environment and ecosystem: while they block sun and shade the ground, they can sometimes trap heat. They also transport water around the globe, affecting moisture, rainfall, vegetation, and more.
A related and similarly important element of the Arctic climate system is aerosols, the tiny airborne particles which clouds form around. Atmospheric modeling studies have pointed to aerosols as significant contributors to the Arctic’s rapid warming, but little is known about the sources, sinks, and interactions of Arctic aerosols and how these factors affect cloud formation and climate. Building a more comprehensive understanding of the aerosols present in the Arctic and how they interface with the broader climate system is critical to predicting this changing environment’s future and its impact on the rest of the world.
In this study, researchers from the Pacific Northwest National Laboratory analyzed winter Arctic aerosol particles at the Advanced Light Source (ALS) to determine their chemical composition, providing insights on where they come from and how they interact with clouds and other elements.
From Svalbard to Berkeley
Samples of Arctic aerosol particles made the long journey from a research collection site near the Gruvebadet Atmospheric Laboratory in Ny-Ålesund, Svalbard, Norway, all the way to the ALS in Berkeley, California.
Using scanning transmission x-ray microscopy (STXM) at ALS Beamline 5.3.2.2, the research team examined each particle to obtain precise x-ray absorption data. Peaks in the absorption spectra corresponded to organic functional groups, revealing the chemical makeup of individual particles.
“We examined over 25,000 individual particles of Arctic air one by one—almost like looking at each grain under a powerful microscope to see what it is made of, how big it is, and what it is mixed with,” said Swarup China, a chemist at Pacific Northwest National Laboratory and corresponding author on the study.
Based on the chemical makeup of each particle, the researchers could draw conclusions about where it may have come from, its age, and what else it may have interacted with.
“STXM allowed us to see not only how much carbon was present in each particle, but details about its chemical state, which hold clues to the origin and history of the particle,” said Matthew Marcus, staff scientist at Beamline 5.3.2.2.
Sea salt with a dash of mineral dust
Most of the particles were coated with organics, indicating that they were sea salt coming from the ocean and blowing snow. Many of them had reacted with other other particles and gases during their time in the atmosphere. These events changed their chemistry in ways that could affect how they interact with sunlight and clouds.
Some sea salt particles were mixed with mineral dust. Because sea salt helps form liquid droplets, while dust helps form ice crystals in clouds, particles with mixed composition of sea salt and dust may be especially good at helping clouds form.
Together, these analyses shed light on the chemically complex particles of Arctic air that strongly influence the small-scale physics happening inside clouds, solar radiation, and environment. They also highlight the importance of incorporating several processes into Earth system models, including aerosol transport pathways and atmospheric aging, for yielding more accurate forecasts.
“Understanding what these particles are and how they change as they travel could help improve predictions of the Arctic’s future weather and its global impact,” said China.
Z. Lai, Z. Cheng, N.N. Lata, S. Mathai, M.A. Marcus, M. Mazzola, C. Mazzoleni, S. Gilardoni, and S. China, “Chemical Composition and Mixing State of Wintertime Aerosol from the European Arctic Site of Ny-Ålesund, Svalbard,” ACS Earth and Space Chemistry 9 (11), 2607 (2025), doi:10.1021/acsearthspacechem.5c00175.