Asian desert dust could be warming Arctic sea surface, confusing satellites

Asian desert dust could be warming Arctic sea surface, confusing satellites — study

Satellites misread the surface temperature, showing it to be colder than it really is

A dust storm in Beijing in March 2002 from the Gobi Desert. In around 25 per cent of dust storms in Asia, particles travel to the Arctic and contribute to the warming of sea surface temperatures. (Reuters )

 

CBC,

12 September, 2018

Large amounts of dust from Asian deserts could be contributing to the warming of Arctic sea surfaces, but satellites are misreading these temperatures as being colder than they are.

That's according to a recent study  published in Scientific Reports by Ron Vincent, an associate professor in the department of physics and space science at the Royal Military College of Canada in Kingston, Ont. He studies sea and water surface temperatures in the Arctic.

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"I don't think people think about the Arctic as being a particularly dusty place, and I don't think it's well known just how much dust is being transported to the Arctic," he said.

Approximately 6.5 million metric tons of dust are deposited north of 60 every year, much of it coming from deserts in Asia, according to another study cited in the paper. 

Vincent said he hopes to look at older satellite data to see if the amount of dust has increased over time and if it's more widespread in the Arctic. He also wants to look at the Antarctic.

Ron Vincent says research has shown dust travels through the atmosphere from the Gobi and Taklamakan deserts and deposits on ice, snow and water in the Arctic in a matter of days. (CBC)

About 25 per cent of dust storms in Asia transport particles directly to the Arctic — mainly from the Gobi and Taklamakan deserts. Smaller contributions also come form the Sahara Desert in North Africa.

The dust travels through the atmosphere and deposits on ice, snow and water in a matter of days, Vincent said.

He saw the phenomenon while looking at satellite images of the Amundsen Gulf and Great Bear Lake in the Northwest Territories taken between 2007 and 2017. He said surface temperatures were much colder than he expected and he was "astounded" when he discovered a layer of dust covering the surface.

"From space, it has a signature of a desert on the water, which to me was pretty remarkable," he said. "I hadn't seen that, at least in the Eastern Arctic with the studies I've done there."

Satellites misread the surface temperature, Vincent said, because dust doesn't emit energy as efficiently as water or ice surfaces. Therefore, satellites report the temperature as being colder than it actually is. 

But he said when dust is deposited on ice and water it actually causes warming by reducing the reflectivity of the surface. This means it absorbs the energy from the sun's rays rather than reflecting it back into space.

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The Amundsen Gulf region is shown using infrared wavelengths to illustrate the dusty area. (Submitted by Ron Vincent)

Vincent said that while dust storms are naturally occurring, human activities are still a big contributor to climate change. 

"With global warming, we're seeing more and more drylands, and we're seeing more dust storms occurring and more violent dust storms. So what this implies is that we can expect more dust coming to the Arctic with time," he said.