For the first time ever, loss of sea ice is leading to large waves in the Arctic Ocean. During a peak period, an average of 16-foot waves were recorded. Waves as tall as 29 feet were recorded in an area that was not long ago permanently covered in ice.

The findings, from a study published in Geophysical Research Letters, is concerning not only because it appears to be a fast-moving sign of climate change, but the large waves can also lead to more sea-ice loss.

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“As the Arctic is melting, it’s a pretty simple prediction that the additional open water should make waves,” lead author Jim Thomson, an oceanographer with the UW Applied Physics Laboratory, said in a statement. Wave size increases with travel distance over open water.

The possibility of an ice-free season in the Arctic opens the possibility of shipping in the region. But large waves increase risk.

“Almost all of the casualties and losses at sea are because of stormy conditions, and breaking waves are often the culprit,” Thomson said.

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The new research was taken in deep water in the Beaufort Sea north of Alaska. The researchers plan to be part of an international group that will place dozens of sensors in the Arctic Ocean to learn more about ice retreat in the region.

“The melting has been going on for decades. What we’re talking about with the waves is potentially a new process, a mechanical process, in which the waves can push and pull and crash to break up the ice,” Thomson said.