Arctic ice is melting faster than expected — and the culprit could be dust

Yahoo

16-03-2025

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NASA's most ambitious Arctic voyage to date has revealed surprisingly high concentrations of ice particles in clouds over Greenland, a clue that may help explain why Arctic ice is melting even faster than predicted.
"The Arctic is changing faster than anywhere else on the planet, so the question we're trying to ask here is: Is the Arctic going to change fast — or really fast?" Patrick Taylor, the deputy science lead for the mission known as ARCSIX, for Arctic Radiation Cloud Aerosol Surface Interaction Experiment, told Space.com.
This bold mission to one of the world's most forbidding regions involved sending a small fleet of instrument-laden planes, including a NASA C-130 and a P-3 Orion, to dart through Arctic clouds and drop buoys into gaps in iceberg-laden waters below. While agency scientists are still studying the data, which was collected last summer, they say it's already clear that dust from Greenland's increasingly exposed landmass is melting vulnerable sea ice toward northern parts of the globe.
It's like a self-reinforcing feedback loop that spells danger for one of the planet's most vulnerable regions.
The ARCSIX plane flew in the summer of 2024, from May until July 25, when seasonal sea ice melt was at its height. The team expected to find ice with a thickness of about 11.5 feet (3.5 meters); instead, they saw a thickness of just 7.2 feet (2.2 meters). "It's alluding to the fact that this thicker sea ice north of Greenland is not as sustainable as it once was," Linette Boisvert, the ARCSIX cryosphere lead, told Space.com.
The Arctic has lost about 12% of its ice every decade since satellite records began in 1979, equaling about 1.16 million square miles of ice (3 million square kilometers),an area bigger than Alaska, Texas, California and Montana combined — and the pace appears to be visibly accelerating, with Arctic sea ice now shrinking at a rate of 12.2% per decade, six times as fast as the 1990s.
Specifically, NASA launched ARCSIX to try to find out how long the sea ice in the Arctic had left, and the summer of flying yielded "the most comprehensive set of sea ice, cloud, radiation and aerosol measurements ever collected in the Arctic," Taylor said.
Collecting so much data in such a remote place was an extreme logistics challenge, requiring a team so large that NASA had to rent extra seats on a Space Force transport plane to ship cargo and extra supplies. "I get shivers just thinking about it," Christina McCluskey, a climate scientist at the National Center for Atmospheric Science, told Space.com. One of the transport flights to Pituffik Space Base in far northeastern Greenland carried a NASA flag, a gift from the U.S. Space Force to the base commander, who displayed it proudly in the base coffee shop and community center.
To measure the thickness of the ice, NASA dropped buoys with thermometers attached to gaps between the floating ice. It was a tricky operation: some of the buoys were smashed apart by icebergs, while others were under threat by curious animals — which is one reason the buoys had to be painted white.
"If you make them a different color, polar bears become attracted to them and will destroy them,' says Taylor. Over time, he said, the surviving buoys will yield valuable data. "Because those buoys are simple points, the aircraft data that we took will tell us spatially what's the variability of that sea ice thickness … putting the two together will give us a clear picture of how thick this multi-year ice is."
Climate models — scientific estimates of how the Earth's climate might change in the future — run on supercomputers that have to process enormous amounts of data every day as clouds form and dissipate all over the world. One aspect of these models concerns particles within clouds, which are sometimes only nanometers wide, that need to be scaled up and measured across the surface of the Earth.
"The scales we need to understand are insane," says McCluskey. "Clouds are the most fascinating things on the planet, I see them as the way in which everything comes together."
NASA scientists looking at seven years of satellite data had previously found that 4.5% of clouds below 15 degrees Celsius (59 degrees Fahrenheit) changed from liquid to ice when they became dusty. The scientists estimated that the clouds contained 93 nanograms of dust per cubic meter — but results from the ARCSIX mission are expected to reveal far higher dust concentrations.
"We're trying to figure out why we're finding all this ice in the clouds," says Taylor. "The answer could help scientists understand the pace of Arctic melt."
Clouds reflect sunlight and slow down the melting of ice, protecting the Arctic. Ice crystals make clouds heavier and more likely to dissipate, leaving the ice vulnerable to rays of hot sun. But the ice can't form in the clouds without something to latch on to. That's where the dust comes in, providing a kind of "seed" or "nucleus" for the ice to form around.
NASA scientists hypothesize that as the ice retreats, more of Greenland's exposed landmass is shedding dust, which is then carried north by heavy winds to form ice particles in the clouds above. These dust-heavy clouds then disappear more quickly and leave more Arctic ice exposed, hastening the melt.
"The sea ice north of Greenland had a giant opening in it in the summer months," says Boisvert. "We think it's caused by really warm, moist air being blown through Fram Strait,' a passage between Greenland and Svalbard, "up and towards the central Arctic."
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Further analysis of the data the team collected is expected to shed light on how quickly the Arctic will lose its ice.
"That's why these results are so important because they help quantify the amount of ice crystals and we can start plugging that into our models to understand how clouds will change," Julia Schmale, a German scientist who specializes in aerosols and their interactions with clouds, told Space.com.