Sixteen-foot waves are buffeting an area of the Arctic Ocean that until recently was permanently covered in sea ice—another sign of a warming climate, scientists say.

Because wave action breaks up sea ice, allowing more sunlight to warm the ocean, it can trigger a cycle that leads to even less ice, more wind, and higher waves. (See "Shrinking Arctic Ice Prompts Drastic Change in National Geographic Atlas.")

Scientists had never measured waves in the Beaufort Sea, an area north of Alaska, until recently. Permanent sea ice cover prevented their formation. But much of the region is now ice-free by September, and researchers were able to anchor a sensor to measure wave heights in the central Beaufort Sea in 2012.

"It is possible that the increased wave activity will be the feedback mechanism which drives the Arctic system toward an ice-free summer," write Jim Thomson of the University of Washington in Seattle and Erick Rogers with the Naval Research Laboratory (NRL) in Mississippi in the journal Geophysical Research Letters.

If winds can blow for a longer distance over the open ocean, they can produce higher and higher waves. Sea ice limits how far winds can blow, thus limiting the formation of waves.

"Future scenarios for reduced seasonal sea ice cover in the Arctic suggest that larger waves are to be expected," the study authors write. (See "As Sea Ice Shrinks, Can Polar Bears Survive on Land?")

Big waves could be the new normal in the Arctic, says Darek Bogucki, a physical oceanographer who works in the Arctic but wasn't involved in the study.

That means changes for shorelines, which could start getting hit with larger and larger waves that speed erosion, he says. It could also change the amount of carbon dioxide being exchanged between the atmosphere and the ocean, potentially triggering the Arctic to release more greenhouse gas into the atmosphere.

The amount of open water varies annually in the Beaufort, with virtually no open water in April when sea ice is at its maximum, to over 621 miles (1,000 kilometers) during sea ice minimums in September. Although the Arctic has been steadily losing its sea ice cover since the late 1970s, that loss accelerated in 2002. The 16-foot (five-meter) waves the scientists' instrument picked up occurred during a storm with strong winds on September 18, 2012.