It would seem that the sterile vacuum of space is not much “cleaner” than the earth’s, where cosmic dust constantly falls down and covers the surface of our planet. Now researchers have found a way to trace Arctic sea ice cover by analyzing the presence of cosmic dust in seafloor sediments, reconstructing the ice cover over the past 30,000 years.
Today, the decline in Arctic sea ice is monitored by satellites, but the findings outlined in Science will allow us to look much further into the past, helping to improve predictions of sea ice behavior under current climate change scenarios.
Read more: The latest news from the Arctic is mixed – and that's not good
How space dust is linked to Arctic sea ice
When comets collide and stars explode cosmic dust is born. As this dust travels through space, it picks up helium-3, an isotope rare on Earth, which makes space dust easily distinguishable from terrestrial sediments as it settles on the planet's surface.
Knowing that cosmic dust falls to Earth constantly and evenly, the researchers hypothesized that this could help track sea ice coverage based on the amount found in ocean sediments below. Think about Arctic ice like an umbrella protecting the seabed from cosmic dust, the size and extent of which depend on the climate of the time. Long-term records Arctic sea ice are few in number, so filling this gap could help predict future climate impacts.
“If we can predict the timing and spatial patterns of future ice cover decline, it will help us understand warming, predict changes in food webs and fisheries, and prepare for geopolitical shifts,” said study lead author Frankie Pavia, assistant professor of oceanography at the University of Washington, in the paper. press statement.
Tracking Arctic ice cover during the last ice age
The research team extracted sediment cores from three different sites: one near the North Pole (with year-round ice), a second near the edge of seasonal ice during its lowest cover in September, and a third from a site that was once covered year-round in 1980 but now freezes only in winter.
Analyzing the nuclei was not easy.
“There's a little bit of cosmic dust falling all over the place, but terrestrial sediments are also accumulating quite quickly,” Pavia explained. By measuring traces of helium-3, the samples showed that year-round ice corresponds to reduced amounts of cosmic dust. Overall, the team reconstructed the history of sea ice over the past 30,000 years, according to the press release.
The results matched what we know about the latter ice age – about 20,000 years ago – when almost no cosmic dust was found in the sediments. When sea ice retreated during deglaciation about 15,000 years ago, cosmic dust began to reappear in the cores.
Less ice, more nutrients in the ocean
While doing this, the researchers also examined how the availability of nutrients in the cores relates to sea ice cover. Nutrient uptake was highest when ice cover was lowest, and the team expected to “see increased nutrient uptake by phytoplankton in the Arctic, with implications for the food web.”
Marine ecosystems are fragile, and sudden increases in nutrients can alter or even destroy habitats, affecting regional productivity. The team suspects that less ice allows for more photosynthesis, which in turn leads to increased nutrient uptake, although other scenarios, such as nutrient dilution by meltwater, are also possible.
More research is needed to uncover this connection, but studies like these provide further evidence that to understand Earth's history, we sometimes have to look to the stars.
Read more: Space dust associated with Earth came from the edge of the solar system
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