Researchers from the University of Washington have discovered how cosmic dust particles can tell us about the thousands of years of history of Arctic ice. The research results were published in the journal Science.
Since 1979, when satellites began regularly measuring sea ice, its extent has decreased by more than 42%. As the ice thins and recedes, open water absorbs more heat from the sun, accelerating warming and further ice loss. Climate projections show that Arctic summers could experience ice-free periods in the coming decades, affecting ecosystems and humanity.
“If we can understand where and when the ice will disappear, it will help predict changes in ecology, fisheries and even geopolitics,” said Frankie Pavia, assistant professor of oceanography who led the study.
Ice traces in cosmic dust
Cosmic dust is formed in the explosion of stars and the breakup of comets. Particles passing close to the Sun carry a special isotope helium-3. Its content helps distinguish cosmic dust from ordinary terrestrial precipitation.
“It was like looking for a needle in a haystack. The particles fell everywhere but the ground quickly covered them,” Pavia said.
Scientists are especially interested in areas with the least dust. During the Ice Age, Arctic sediments contained virtually no cosmic particles – suggesting the ice cover was stable.
The researchers sampled marine sediments from three Arctic regions and measured the content of cosmic dust. Ice blocks particles from settling, while open water allows them to reach the bottom. By comparing sediment layers, the team reconstructed changes in ice cover over more than 30,000 years.
“Our locations include different modern ice zones. One, near the North Pole, is icy all year round, the second is seasonal, the third used to always be covered with ice, but now sometimes there is no ice at all,” Pavia explains.
Periods of stable ice coincided with low levels of cosmic dust. As the climate warms, dust begins to fall back as rain, exposing the open water surface.
The effect of stone on nutrients
Comparing ice cover reconstructions with nutrient data shows that nutrient uptake is greatest when ice cover is low and decreases as ice grows. Scientists have obtained information from the microscopic shells of foraminifera – marine creatures that leave chemical traces of nitrogen consumption.
“If ice decreases, phytoplankton will consume more nutrients, which will affect the entire food chain,” Pavia said.
The exact reasons why this happens are still unclear. It's possible that less ice would increase photosynthesis at the water's surface, increasing nutrient uptake. Another theory is that melting ice reduces nutrient concentrations in the water. The first explanation points to an increase in ecosystem productivity, the second to a redistribution of resources.
The study's findings suggest that cosmic dust could provide an unusual but powerful tool for studying the history of Arctic ice formation and predicting future changes in ecosystems and climate.
