Arctic sea ice, already suffering the onslaught of warming temperatures, faces another unanticipated risk as giant 16-foot swells have been observed in the normally calm ocean waters of the region, researchers say.
Swells that big can break up sea ice even more quickly than the melting that has been ongoing there from decades of global warming, they say.
Scientists say they were shocked to find the giant waves in the Beaufort Sea north of Alaska, since the area is covered in ice most of the year, lacking the open water on which sea winds can work to create large surf.
Open water, created as a result of warming-driven melt, could span the entire Arctic Ocean by the middle of the century, researchers who made a first analysis of waves in the Arctic Ocean in 2012 reported in the journal Geophysical Research Letters.
High winds that continuously blow through the Arctic, together with the increasing presence of open water areas in summer, have the potential to create huge swells that can assault the ice cover with tremendous energy, they said.
"As the Arctic is melting, it's a pretty simple prediction that the additional open water should make waves," says study lead author Jim Thomson, a University of Washington oceanographer.
As those waves break up large expanses of sea ice, a feedback loop could see the newly opened water subjected to more winds creating yet more and bigger waves, he says.
"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 and his colleague W. Erick Rogers of the Naval Research Laboratory gathered the wave measurements using sensors anchored on the sea floor 150 feet under the surface of the Beaufort Sea.
The researchers say they're in the process of putting dozens of similar sensors in the Arctic Ocean to analyze the physics of sea ice retreat and the increasing presence of heavy seas.
The data could be important as shipping and oil exploration taking advantage of an expanding ice-free season in Arctic Ocean waters faces increasing risks from big waves, Thomson says.
"Almost all of the casualties and losses at sea are because of stormy conditions, and breaking waves are often the culprit," he says. "At this point, we don't really know relative importance of these processes in future scenarios."
