Trials in Canada and Norway Show Sea-Ice Thickening Increases Ice Depth but Yields Varied Effects on Summer Melt

Two companies conducted separate trials to thicken Arctic sea ice by pumping seawater onto the surface and allowing it to freeze. The Real Ice trial in Canada and the Arctic Reflections trial in Norway both increased ice thickness, but produced different outcomes regarding summer melt timing.

The Real Ice trial took place between December 2024 and February 2025 at eight sites in the Northwest Passage just south of the Inuit village of Cambridge Bay, Canada.

Researchers flooded and froze the snow layer over a total of 250,000 square metres, thickening some sites twice. 62 metres at three control sites. Long wires of temperature sensors drilled into the ice suggested the test sites in Canada melted more slowly than the historical average, lasting an estimated seven to 10 extra days.

Real Ice test sites showed up as white spots amid blue meltwater in satellite imagery in June. Canadian researchers stated that thickening slowed the ice’s melt in summer. The Arctic Reflections trial occurred in April 2024 in a lagoon in the Svalbard archipelago.

The team drilled a hole through nearly a metre of ice and pumped seawater onto a roughly 20-centimetre layer of snow for a little over an hour. 16 metres. A camera left at the Arctic Reflections site through June showed the thickened ice melted away on the same day as a control site.

Norwegian researchers found that thickening did not delay melting. The Arctic Reflections study estimated that the cooling effect barely compensated for the warming from pump and vehicle emissions. When seawater freezes, it expels salt as a briny liquid.

The thickening process heated the sea ice and made it saltier as brine drained through pores. Both trials found thickening made ice brighter. Christian Haas at the Alfred Wegener Institute in Bremerhaven, Germany, who worked on analysing the Norway trial results, said the brine pores could affect melt rates.

Both groups have continued doing trials after the 2024-2025 tests. 9 million UK government grant, which is also funding Real Ice and Arctic Reflections. According to Real Ice, someday 500,000 underwater drones could refreeze 1 million square kilometres of sea ice using heated hoses.

Last year, 42 scientists authored an article arguing 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 any of the research, 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.

1029/2025JC022738.

1029/2025EF007894.