A massive dust storm streaming from northern Africa across the Atlantic Ocean in February 2006.

Credit: SeaWiFS/NASA

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SAN DIEGO: The retreat of glaciers and the loss of moisture from soil due to climate change will likely increase the number of large-scale dust storms, such as those that blanketed Sydney in 2009, scientists predict.

“Every year, hundreds of millions of tonnes of African dust are carried westward across the Atlantic to South America, the Caribbean and to the North America,” as well as across the Mediterranean and the Middle East, said Joseph Prospero, an atmospheric chemist at the University of Miami.

His group has been measuring global dust plumes from a site in Barbados since 1965 – the longest dust storm data so far collected – and matching it with satellite images.

Whitish haze for several days

The storms create a whitish haze in the summer skies for several days, depositing a thin film on homes and cars in southern USA and the Caribbean.

Data from a collecting site established in Iceland in 1991 shows similar dust storms over the Arctic, which dump fine soil over North America and northern Europe.

His group believe they most come from retreating glaciers, he told a meeting of the American Association for the Advancement of Science in San Diego.

"Huge spike"

“Every huge spike we see in our samples – we’re talking about hundreds of micrograms per cubic metre of dust – we can identify in satellite images, from the most part, from para-glacial deposits in the five major glaciers on Iceland,” Prospero said.

“These glaciers are retreating, and if they continue to retreat, then you’re going to be exposing more of this sub-glacial grinding,” leading to more dust fallout over Britain and Europe, he added.

Scientists have long known that the grinding of rock by massive ice sheets during the last ice age created the rich soils of Europe and North America.

“Glaciers are profound producers of fine-grained particles through the rock-grinding process that creates ‘rock flour’,” said Daniel Muhs of the U.S. Geological Survey in Denver.

“There were periods in the Earth’s past that were dustier than now … and those primarily correspond with glacial periods,” he added.

But the science is still in its infancy, and scientists are only now beginning to unravel the complex relations between dust, ice, atmosphere and the oceans, and there is still much that is unknown about the airborne distribution of fine solid particles around the world, scientists said.