“This would have been a wild dream a year ago,” says Andrea Ceccolini, standing on Arctic sea ice just a 4-mile snowmobile ride from the Inuit town of Cambridge Bay, northern Canada. To his left are sky blue ponds of meltwater created in the last few days by a sun that no longer sets in the high north summer. To his right, the sea ice is still a brilliant white, the light dusting of snow on top continuing to sparkle.

“It’s incredibly different, the boundary – I mean, you can point to it,” he says. The difference is the result of a bold geoengineering experiment being conducted by Ceccolini’s company, Real Ice, funded by the UK government.

Five months earlier, the team had braved temperatures of -40C on the sea ice to drill holes and pump 50,000 tonnes of ocean water up on to its surface. It froze almost immediately, thickening the 1.5-metre-deep ice by about 50cm, according to the new measurements. That has protected the ice, at the start of the melt season at least, and is an early sign that one day, perhaps, it may be possible to refreeze a significant part of the Arctic.