Dust storms could be having a bigger effect on climate change than we thought

Dust from the Copper River Valley is more effective at forming ice than dust from the Sahara, study finds

Alaskan dust storms appear to play a significant role in atmospheric ice formation. Photo: Sarah Barr

Dust storms in the Gulf of Alaska might play a pivotal role in influencing global climate patterns, a study has revealed.

These Alaskan dust particles, especially from the Copper River Valley, have been found to be more efficient at forming ice in the atmosphere compared with those from the Sahara, shedding new light on the complexities of our climate system.

Giant dust storms originating in the Gulf of Alaska can persist for days, releasing tonnes of silt into the atmosphere.

Their scale is such that they have been spotted from space, with images from the Landsat satellite in 2020 capturing dust being carried from the valley to Alaska’s southern coastline.

While the exact implications of these dust particles on global climate are a mystery, research by the University of Leeds and the National Centre for Atmospheric Science suggests a more profound effect than previously believed.

Historically, climate research predominantly concentrated on dust contributions from the Sahara and regions in Africa and Asia.

Prof Benjamin Murray, lead researcher, told The National: "Dust from places like the Sahara has long been known to be important for the planet’s climate. It reflects sunlight back into space so affects climate directly."

These mid to low-latitude storms introduce desert-sourced dust particles into the atmosphere.

However, researchers at Leeds chose a different path, examining the dust from the Copper River Valley on Alaska's south coast, which stretches more than 443km.

Prof Murray said: "One major difference is that Copper River Valley dust has some biological material mixed up in it which makes it much better at nucleating ice.

"The more ice-nucleating particles, the more ice in clouds ... and consequently stratoform clouds out over the oceans tend to reflect less sunlight to space with more absorbed at the surface."

This river is believed to transport about 70 million tonnes of glacial sediment annually.

During warmer months, when water levels are low, winds pick up this silt, dispersing it extensively across North America, sometimes reaching altitudes conducive for ice-cloud formation.

Distinct from Saharan dust, the Copper River Valley particles have a richer biological composition due to the area's abundant vegetation and wildlife.

Dust's role in atmospheric ice formation is pivotal. Without dust, cloud water can remain liquid even in freezing temperatures.

Prof Benjamin Murray, an atmospheric scientist at Leeds, said: “Only a tiny fraction of atmospheric dust particles have the ability to initiate ice formation.

“We are only beginning to understand their origins and global spread. A cloud's ability to reflect sunlight is determined by its ice content, thus it's imperative to understand the diverse sources of these ice-nucleating agents globally.”

Existing climate models largely ignore these high-latitude dust sources, a deficiency highlighted by Prof Murray.

Sarah Barr and Bethany Wyld, doctoral researchers at Leeds, collected samples during these dust storms.

Subsequent laboratory analysis revealed that the particles from Alaska excel in forming ice, compared with their Saharan counterparts.

This difference arises from the Alaskan dust's microscopic biogenic substance fragments, remnants of living organisms.

Meanwhile, Saharan dust comprises mostly potassium feldspar, a significant ice nucleating agent in such regions.

Emphasising the study's significance, Ms Barr said: “While the Sahara's importance in supplying ice-nucleating particles is acknowledged, our research underscores river deltas like the Copper River Valley's equally vital role. Comprehensive understanding of these dust emissions is essential for refining our climate models.”