Clouds tell us what type of weather to expect, and wield a great deal of influence over our climate. They can enhance warming by trapping heat or cool the planet by reflecting sunlight back into space. Atmospheric scientists are studying another influencer with outsized effect: dust.
Dust can transform clouds, thereby altering the climate. With global temperatures rising and glaciers receding, the Arctic has been getting a lot dustier lately.
“As the Arctic climate changes, and the land/ocean surface properties change, impacts of particle emissions on cloud properties need to be considered as part of the story,” explained Paul DeMott, one of the Colorado State University atmospheric scientists who recently participated in an international study of glacially sourced dust and its impact on cloud formation. Their findings were published in Nature Geoscience on March 25.
This study, led by former CSU researcher Yutaka Tobo, was among the first to consider dust originating in the Arctic, rather than from the usual suspects, arid and semi-arid regions.
As glaciers melt, dust is left in their wake. Some of this dust is picked up and lofted high in the atmosphere, where it can act as the foundation for ice crystal formation in clouds. Icy clouds are less reflective than water-based clouds, which scatter more light back to space. These “glaciated” clouds also are more susceptible to precipitation, which shortens their life span and modifies the hydrological cycle.
To determine the origin of these ice-nucleating particles, researchers took soil and particle samples in glacial outwash plains in Svalbard, an archipelago in the Arctic Ocean between mainland Norway and the North Pole. Lab experiments then assessed the composition and freezing properties of collected particles and soils.
Researchers did not expect to find such high activity of biogenic ice-nucleating particles in soil with such low organic content, but the results explain the observed increase in particles capable of seeding ice and precipitation formation in clouds in Svalbard’s air during summer.
“It surprised me that what would be considered poor soils were so full of these special particles that come originally from biological processes,” DeMott said. “It also surprised me that high latitude dust sources can dominate over transports from other major global dust sources at certain times of the year, yet have been largely ignored.”
University Distinguished Professor Sonia Kreidenweis and DeMott’s research group, based in the Department of Atmospheric Science, is a global leader in the study of ice-nucleating particles and their impacts on clouds and climate. Other participating researchers from the group included Tom Hill and Jun Uetake.
The international research team plans to advance its knowledge of glacially sourced dust and its implications through both field studies of cloud systems and numerical modeling.
“We hope to capture more of the annual cycle of ice-nucleating particles in air in many Arctic regions, and to investigate these with better physical, chemical and biological analysis,” DeMott said.