Geoengineering can thicken Arctic sea ice, but for how long?

geoengineering can – Field trials in Canada and Norway have shown that pumping seawater onto Arctic sea ice can thicken it—yet the results differ on whether that extra thickness actually delays the ice’s eventual summer melt. Researchers say the ice can be made brighter, but salt-

In winter, Canada already clears a path across frozen lakes by drilling holes and pumping water onto ice until it thickens enough to carry heavy vehicles. The same idea is now being tested on a far harder target: Arctic sea ice.

The stakes are plain. Arctic sea ice is expected to disappear completely in summertime as early as the 2030s, and that loss matters because sea ice reflects more of the sun’s warmth back into space than open ocean.

In field trials in Canada and Norway in 2024 and 2025, geoengineering researchers tried to see whether thickening could buy time. Both trials managed to make the ice thicker, but scientists in Canada said the melt slowed when summer came, while those in Norway reported it did not.

That gap is where the question sharpens: not whether pumping can add ice, but how long it changes the outcome.

Christian Haas at the Alfred Wegener Institute in Bremerhaven, Germany, who worked on analysing the Norway trial results, put it directly: “Yes, the ice is getting thicker, but how it delays the eventual disappearance of the ice remains an open question.”

In Norway’s Svalbard archipelago. Arctic Reflections drilled a hole through nearly a metre of ice in a lagoon in April 2024 and inserted an ice road pump. For a little over an hour. a stream of seawater flooded the roughly 20-centimetre layer of snow sitting on top of the ice. The team repeated the process the next day, building a 1500-square-metre puddle of slush. It froze hard within the next three days, increasing the total sea-ice thickness from 90 centimetres to 1.16 metres.

A camera left at the site through June showed a difference that looked encouraging at first. The thickened ice began “rotting” later. But ultimately it still melted away on the same day as a control site in the lagoon.

Across the Atlantic. Real Ice ran a larger programme in Canada’s Northwest Passage. just south of the Inuit village of Cambridge Bay. Between December 2024 and February 2025, the UK company drilled holes and pumped water onto sea ice at eight sites. The researchers flooded and froze the snow layer over a total of 250,000 square metres, thickening some sites twice.

By May 2025, the average thickness at the sites flooded in January and February reached 1.93 metres, compared with 1.62 metres at three control sites.

What happens after the ice is thickened may depend as much on chemistry as on measurement. When seawater freezes, it expels salt as briny liquid. The thickening process heated the sea ice and made it saltier as this brine drained through pores in the ice.

Haas worries that if the thickened ice stays saltier and more porous into the melt season, it could speed up melt. “It’s not about the thickness, but about the quality of the ice,” he says—using an image from the road itself, where salt makes ice less stable.

Real Ice’s Andrea Ceccolini offers a different concern: the brine pores could drain meltwater and slow the ice’s disappearance. In Canada. long wires of temperature sensors drilled into the ice suggested the test sites melted more slowly than the historical average. lasting an estimated seven to 10 extra days.

Light also appears to shift. Both trials found thickening made ice brighter. In June satellite imagery, Real Ice’s test sites showed up as white spots amid blue meltwater. “We were contributing to reducing the heating of the planet,” Ceccolini said.

Yet Arctic Reflections’ study estimated that the cooling effect barely compensated for warming caused by pump and vehicle emissions.

The work is far from finished. Michel Tsamados at University College London said a few years of research are needed to assess whether thickening could help preserve Arctic sea ice. He is working on modelling. supported by a £9.9 million UK government grant that is also funding Real Ice and Arctic Reflections.

Tsamados’s challenge isn’t only scientific—it’s logistical and moral in its own way, because it forces the question of where, and how far, humans might go. “It can work locally,” he says. “Then what about 10 kilometres? What about 100 kilometres? Should it be done?”

The uncertainty stretches beyond climate metrics. The effects on wildlife—including ice algae, polar bears, or seals—aren’t clear.

Real Ice has floated an ambitious future scenario: if sea-ice thickening proves feasible, it could one day involve 500,000 underwater drones refreezing 1 million square kilometres of sea ice, with melting downward through the ice as heated hoses do their work.

Arctic Reflections, meanwhile, is considering refreezing a few crucial areas—such as straits where sea ice flows south to melt.

But the trials don’t land in a vacuum. Last year. an article signed by 42 scientists argued that polar geoengineering. including sea-ice thickening. was unfeasible and could distract from reducing emissions. Michael Meredith at the British Antarctic Survey. who wasn’t involved in either study. said: “This technique might have limited use as a small-scale stopgap in some localised regions. but it doesn’t represent a practical large-scale solution.”.

Even as engineers and researchers prove they can thicken sea ice, the most human part of the problem remains: deciding what “thickening” is supposed to achieve—an extra day, a delay measured in weeks, or simply a stopgap against a loss that already has a timetable.

For now, Canada and Norway have added ice to the Arctic’s surface. Whether that ice buys meaningful time—and whether the trade-offs are worth the effort—will determine whether this stays a field experiment or becomes something far larger.

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