Scientists have used cosmic dust to reconstruct 30,000 years of Arctic sea ice history, showing dramatic shifts tied to climate changes. The study, published in Science, links ice coverage to nutrient cycles and future ecological impacts. Findings highlight how declining ice could boost phytoplankton activity and alter food webs.
Arctic sea ice has shrunk by more than 42% since 1979, when satellites began consistent measurements. As ice thins and retreats, exposed ocean absorbs more sunlight, accelerating warming and potentially leading to ice-free summers in coming decades.
A study published on November 6 in Science utilized cosmic dust—fine particles from exploding stars or disintegrating comets carrying helium-3—to track ancient ice coverage. Researchers measured helium-3 in sediment cores from three Arctic sites spanning modern ice gradients: one near the North Pole with year-round coverage, another at the seasonal edge in September, and a third that was ice-covered in 1980 but now sees periodic open water.
"It's like looking for a needle in a haystack," said Frankie Pavia, a University of Washington assistant professor of oceanography who led the research. "You've got this small amount of cosmic dust raining down everywhere, but you've also got Earth sediments accumulating pretty fast."
The analysis revealed minimal cosmic dust during the last ice age around 20,000 years ago, indicating persistent ice that blocked dust from reaching the seafloor. As the planet warmed post-ice age, dust reappeared in sediments, signaling reduced ice.
Linking ice to biology, the team found nutrient consumption by foraminifera—measured via chemical signatures in their shells—was highest during low-ice periods. "As ice decreases in the future, we expect to see increased consumption of nutrients by phytoplankton in the Arctic, which has consequences for the food web," Pavia said.
Possible drivers include enhanced surface photosynthesis from less ice or dilution of nutrients by meltwater, though more research is needed to distinguish productivity gains. "If we can project the timing and spatial patterns of ice coverage decline in the future, it will help us understand warming, predict changes to food webs and fishing, and prepare for geopolitical shifts," Pavia added.
Co-authors include Jesse R. Farmer from the University of Massachusetts Boston, Laura Gemery and Thomas M. Cronin from the U.S. Geological Survey, and Jonathan Treffkorn and Kenneth A. Farley from Caltech. The work was supported by the National Science Foundation and a Foster and Coco Stanback Postdoctoral Fellowship.