Space dust on the ocean floor helps solve the puzzle of Arctic ice from 30,000 years ago
The seemingly barren void of space isn’t much “cleaner” than Earth, with cosmic dust constantly raining down and covering our planet’s surface. Now, researchers have found a way to trace Arctic ice cover by analyzing the presence of space dust in seafloor sediments, reconstructing ice cover over the past 30,000 years.
Today, the decline of Arctic sea ice is monitored by satellite, but the results presented in Science allow us to look much further into the past, helping to improve predictions of sea ice behavior under current climate change scenarios.
Learn more: The latest news from the Arctic is mixed — and it’s not good
How space dust is linked to Arctic sea ice
When comets collide and stars explode, cosmic dust is born. During its journey through the cosmos, this dust collects helium-3, an isotope rare on Earth that makes it easy to distinguish cosmic dust from terrestrial sediments once deposited on the planet’s surface.
Knowing that space dust falls to Earth consistently and uniformly, the researchers hypothesized that this could help trace sea ice coverage based on the amount found in the ocean sediments below. Think of Arctic ice as an umbrella protecting the seafloor from cosmic dust, the size and scope of which depends on the climate at the time. Long-term records of Arctic sea ice are rare, so filling this gap could help predict future climate impacts.
“If we can project the timing and spatial patterns of ice cover decline into the future, it will help us understand warming, predict changes in food webs and fisheries, and prepare for geopolitical changes,” said the study’s lead author, Frankie Pavia, assistant professor of oceanography at UW, in a news release.
Tracking Arctic ice cover during the last ice age
The research team collected sediment cores from three different sites: one near the North Pole (with year-round ice), a second near the seasonal ice edge during its lowest coverage in September, and a third at a site that was once covered year-round in 1980 but now only freezes in winter.
Analyzing the cores was not easy.
“There’s a small amount of cosmic dust raining down everywhere, but there’s also terrestrial sediment that’s accumulating quite quickly,” Pavia explained. By measuring traces of helium-3, the samples revealed that year-round ice corresponded to reduced amounts of cosmic dust. Overall, the team reconstructed the history of sea ice cover over the past 30,000 years, according to the press release.
The results agree with what we know about the last ice age – around 20,000 years ago – when almost no space dust was found in the sediments. As sea ice retreated during deglaciation about 15,000 years ago, cosmic dust began to appear in the cores again.
Less ice, more nutrients in the ocean
While they were at it, the researchers also looked at the link between nutrient availability in cores and sea ice cover. Nutrient consumption was highest when ice cover was lowest, with the team expecting to “see increased nutrient consumption by phytoplankton in the Arctic, which would have consequences for the food web.”
Marine ecosystems are delicate and increases in nutrients can alter or even destroy habitats, impacting regional productivity. The team suspects that less ice allows for more photosynthesis, which in turn leads to nutrient use, although other scenarios, such as nutrient dilution by meltwater, are also possible.
More research is needed to uncover this connection, but studies like this prove once again that to understand Earth’s history, we sometimes need to look to the stars.
Learn more: Earth-bound space dust comes from the far reaches of the solar system
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