Space Dust on the Ocean Floor Helps Solve Arctic Ice Puzzle from 30,000 Years Ago
The seemingly sterile vacuum of space isn’t much “cleaner” than Earth, with cosmic dust constantly raining down and coating our planet’s surface. Now, researchers have found a way to trace back Arctic sea ice coverage by analyzing the presence of space dust in seafloor sediments, reconstructing ice coverage over the past 30,000 years.
Today, the decline of Arctic sea ice is monitored by satellites, but the findings outlined in Science allow us to look much further into the past, helping improve predictions of sea ice behavior under current climate change scenarios.
Read More: The Latest News out of the Arctic Is Mixed — and That’s Not Good
How Space Dust Is Tied 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, a rare isotope on Earth that makes cosmic dust easy to distinguish from terrestrial sediments once it settles on the planet’s surface.
Knowing that space dust falls on Earth constantly and evenly, researchers theorized it could help trace sea ice coverage based on the amount found in ocean sediments below. Think of Arctic ice as an umbrella shielding the seafloor from cosmic dust, with its size and reach depending on the climate at the time. Long-term records of Arctic sea ice are scarce, so filling that gap could help forecast future climate impacts.
“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,” said lead study author Frankie Pavia, a UW assistant professor of oceanography, in a press statement.
Tracking Arctic Ice Coverage During the Last Ice Age
The research team recovered sediment cores from three different sites: one close to the North Pole (with year-round ice), a second near the seasonal ice edge during its lowest coverage in September, and a third from a site that was once covered year-round in 1980 but now only freezes in winter.
Analyzing the cores wasn’t easy.
“You’ve got this small amount of cosmic dust raining down everywhere, but you’ve also got Earth sediments accumulating pretty fast,” explained Pavia. By measuring traces of helium-3, the samples revealed that year-round ice corresponded with reduced amounts of cosmic dust. Overall, the team reconstructed the history of sea ice coverage over the last 30,000 years, according to the press release.
The results lined up with what we know about the last ice age — around 20,000 years ago — when almost no space dust was found in the sediment. As sea ice retreated during the deglaciation roughly 15,000 years ago, cosmic dust began appearing again in the cores.
Less Ice, More Nutrients in the Ocean
While they were at it, the researchers also examined how nutrient availability in the cores related to sea ice coverage. Nutrient consumption was highest when ice coverage was lowest, with the team expecting “to see increased consumption of nutrients by phytoplankton in the Arctic, which has consequences for the food web.”
Marine ecosystems are delicate, and surges in nutrients can alter or even destroy habitats, impacting regional productivity. The team suspects that less ice allows more photosynthesis, which in turn drives nutrient use up, though other scenarios, like meltwater diluting nutrients, 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 have to look to the stars.
Read More: Earthbound Space Dust Comes From Solar System’s Edge
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