Understanding the extent of past Arctic ice could help predict how the planet will respond to global warming

Margherita Bassi - Daily Correspondent

November 10, 2025 11:00 a.m.

Researchers studied space dust in ocean sediment cores from the Arctic. Bonnie Light / University of Washington

What did the Arctic look like in the distant past? The answer carries significant implications for understanding how it will change in the future in the context of human-driven global warming. Yet researchers have only been able to directly observe the extent of Arctic sea ice since the dawn of satellite monitoring in 1979—and since then, Arctic sea ice has decreased by more than 42 percent. A study last year projected the Arctic will see its first ice-free day as soon as this decade. To help predict the region’s future, scientists want to better understand its history.

Now, new research may fill in some of the gaps—with a little help from space dust.

Fun fact: Space dust sunsets

Space dust can be seen above the horizon in a “hazy cone of light” right before sunrise and after sunset in the fall and spring months, according to NASA. The glow is created by the sun’s rays as they bounce and scatter off of space dust in the inner solar system. The phenomenon is known as zodiacal light.

In a study published November 6 in the journal Science, researchers used space dust to make a 30,000-year timeline of ice coverage in the Arctic Ocean. The results track how the Arctic’s sea ice has changed over those millennia.

Using space dust as a proxy for ice coverage allows researchers to contextualize future scenarios without direct observations of the extent of ancient ice. “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,” Frankie Pavia, a University of Washington isotope geochemist and lead author of the paper, says in a statement.

Space dust, also called cosmic dust, is produced when stars explode or comets crash into each other. It picks up a rare form of helium called helium-3 when it passes the sun. The researchers used helium-3—as well as a thorium isotope—to differentiate space dust from regular earthly dust. The dust falls onto Earth at a constant rate, often settling onto the seafloor.

So, the team investigated the amount of such dust in ocean sediment cores, hypothesizing that reductions in dust would indicate years that the ocean was covered in ice, blocking the dust from reaching the bottom. They looked at three Arctic sites: One is near the North Pole and is covered by ice all year; another is at the edge of the ice when the ice coverage is at its yearly lowest; and the third is seasonally covered in ice today, even though it was covered all year long in 1980.

The analysis suggests that “the central Arctic was perennially covered by sea ice during the last glaciation,” the researchers write. About 15,000 years ago, they write, sea ice retreated and became seasonal in the warm early Holocene—a period covering the last 10,000 years—before Arctic ice coverage increased again.

The researchers also found that nutrient consumption decreased as ice coverage grew, and it peaked at the lowest level of ice coverage. This suggests that sun-fueled phytoplankton in the Arctic will consume more nutrients as ice continues to melt in the future, with ramifications for the food web. However, further research is necessary to shed light on the forces impacting nutrient availability.

Studying sea ice via space dust “really adds a new tool to our understanding of the Arctic Ocean, which is one of the least understood regions globally,” Walter Geibert, a marine geochemist at the Alfred Wegener Institute who did not participate in the study, tells the New York Times’ Sachi Kitajima Mulkey.

For now, the researchers warn, the results support projections of “a nutrient-starved central Arctic Ocean with continued sea-ice loss.” It remains to be seen how the results of this study affect other predictions about the future of the Arctic and the planet.

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