Scientists are looking below the Arctic seabed for evidence of past ice-free summers
A research expedition to the central Arctic is trying to answer a question that has become increasingly urgent as the region warms: when, if ever in recent Earth history, was the North Pole free of sea ice during summer?
The mission, described by MIT Technology Review, took place in the summer of 2025 aboard the Norwegian research icebreaker Kronprins Haakon. Led by geologist Jochen Knies of the Arctic University of Norway in Tromso, the team traveled from Svalbard toward 90 degrees North with researchers from Norway and Germany. Their goal was to recover long sediment cores from the Arctic seafloor and use them as climate archives.
The journey itself underscored the scale of Arctic change. Knies, who first reached the pole by ship in 1996, recalled the sound of thick ice grinding against the hull on earlier expeditions. In 2025, according to the account, the vessel encountered thin floes and large areas of open water, making for a notably quieter and easier passage.
Why the North Pole’s past matters now
Satellite observations since the late 1970s show that summer ice cover in the Arctic Ocean has declined by more than 40%. MIT Technology Review reports that, in less than half a century, an area of summer ice comparable in size to the Mediterranean Sea has become open water. If the trend continues, the North Pole could soon see summers without sea ice.
One unresolved issue is whether similar conditions occurred during a warmer period about 120,000 years ago. If scientists can determine how the Arctic behaved during that earlier warm interval, they may be able to improve projections for how the region will respond as present-day warming continues.
The expedition is part of a 12.5 million euro project financed by the European Union. Beyond the historical question, the project is also examining how sea-ice loss could affect marine ecosystems, ocean circulation, and the wider climate system.
Sediment cores act as climate archives
The researchers collected sediment cores up to 22 meters long from multiple locations across the Arctic seafloor. These cores are valuable because marine sediments accumulate over time, preserving traces of past conditions in layers of material deposited on the ocean bottom.
Those layers can contain chemical and physical evidence tied to water temperature, sea-ice coverage, plankton remains, weathered rock, and the strength of ocean currents. By analyzing those signals, scientists can reconstruct environmental conditions from periods long before modern satellite observations or ship-based measurements existed.
The central Arctic is especially important because direct evidence from the region is difficult to obtain. Thick sea ice historically made access uncertain even for icebreakers, particularly at the North Pole. As a result, key parts of the Arctic climate record remain incomplete.
The findings could sharpen climate models
The expedition’s importance lies in the gap between what scientists know about recent Arctic change and what they still need to understand about the region’s deeper past. The modern observational record is clear that summer sea ice is shrinking rapidly. What is less clear is how the central Arctic responded during earlier warm periods, and what that response reveals about future thresholds.
If the sediment cores show that the North Pole was ice-free during a past warm interval, researchers may gain a stronger analogue for the coming decades. If the cores suggest persistent ice even during earlier warmth, that would raise different questions about how today’s warming, ocean circulation, and greenhouse gas conditions compare with the past.
Either result would matter because Arctic sea ice is connected to more than regional climate. Ice cover affects how much sunlight the ocean reflects or absorbs, influences marine habitats, and interacts with circulation patterns that can have broader climate consequences.
What to watch next
The source article describes the expedition and its scientific goals, but the core analyses are the next decisive step. Researchers will need to interpret the physical and chemical records preserved in the recovered sediments before drawing conclusions about the North Pole’s past ice conditions.
For now, the expedition marks a direct attempt to extend Arctic climate knowledge beyond the satellite era. As the modern Arctic shifts toward more open water, the record buried under the seabed may help define whether the future resembles any known past or is moving into less familiar territory.
This article is based on reporting by MIT Technology Review. Read the original article.
Originally published on technologyreview.com
