Dust storms in the Gulf of Alaska help shape the global climate

Recent discoveries have cast a spotlight on dust storms in the Gulf of Alaska, revealing their potential role in global climate dynamics.

Dust storms are more than just a visual spectacle. These whirlwinds in the Gulf of Alaska, with their vast expanse, have caught the attention of satellites orbiting the Earth. A 2020 image from the Landsat satellite captured dust spiraling from the valley and embracing Alaska’s south coast.

Could these colossal Alaskan dust storms sway the pendulum of global climate? The answer is shrouded in mystery. 

However, a new study from the University of Leeds and the National Centre for Atmospheric Science suggests that the influence of these storms might be more profound than previously acknowledged.

Focus of the research 

Central to this study is the manner in which clouds react to these sediments. At sufficiently low temperatures, the microscopic fragments – a mix of rock, minerals, and vegetation – morph into ice nucleating particles. 

These act as catalysts, inducing the birth of ice crystals in clouds. But herein lies the conundrum. Depending on the ice content, the number of these particles, and their nature, ice formation in clouds can either intensify global warming or, contrarily, cool our planet. 

The study, published today in the journal Science Advances, emphasizes the pressing need for deeper insight into the role of dust in our intricate climate system.

“Ice-nucleating particles (INPs) influence cloud radiative properties and climate; however, INP sources and concentrations are poorly constrained, particularly in high-latitude regions,” wrote the study authors. 

:Southern Alaska is a known source of high-latitude dust, but its contribution to atmospheric mineral dust and INP concentrations has not been quantified.”

Copper River Valley

Until recently, much of the research in this realm revolved around the easily noticeable Saharan dust storms. These mid to low latitude tempests churn dust from desert terrains into the atmosphere. 

The Leeds team, however, opted for a road less traveled. Their exploration led them to the high-latitude dust source: Alaska’s Copper River Valley. 

Stretching over 275 miles, this river plays conduit to an estimated 70 million tons of glacial sediment annually. And during times of diminished water levels in summer and autumn, the dust gets swept up in the wind, traveling vast distances across North America. 

Here, at these soaring altitudes, the particles play their part in ice formation. But unlike Saharan dust, particles from Copper Valley River possess a richer biological composition due to the lush vegetation and diverse wildlife of the region.

Dust particles and ice formation 

The symphony of ice formation in clouds owes much to dust particles. In their absence, cloud water might defy freezing even at sub-zero temperatures. 

Professor Benjamin Murray is an atmospheric scientist in the School of Earth and Environment at Leeds who supervised the study.

“Only a small fraction of the dust particles in the atmosphere has the capacity to nucleate ice and we are only just starting to understand their sources and global distribution,” explained Professor Murray.

“Whether a cloud becomes more or less reflective of sunlight depends on how much ice is in them, so we need to be able to understand and quantify the various sources of ice-nucleating particles around the globe.  

“At present, climate models tend not to represent these high-latitude sources of dust, but our work indicates that we need to.” 

What the researchers discovered 

Study lead author Sarah Barr and co-author Bethany Wyld, doctoral researchers at Leeds, played storm chasers for the investigation, gathering samples during these dust events. 

Laboratory analysis of the samples delivered a revelation. Alaskan dust particles exhibited superior ice-forming abilities compared to their Saharan counterparts. 

This can be attributed to their rich content of biogenic fragments, relics of once-living organisms. By contrast, desert dust primarily relies on a mineral named potassium feldspar for ice nucleation.

“We knew that deserts like the Sahara are very important at supplying ice-nucleating particles to the atmosphere, but this paper shows that river deltas like the Copper River Valley are also very important,” said Barr.

“Huge quantities of dust are emitted from places like the Copper River, and we need to understand these emissions to improve our climate models.”

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