A wave sensor developed by Thomson during a 2013 test.
(Photo : J. Thomson / UW)
A University of Washington researcher released the first study of waves in the middle of the Arctic Ocean this week, after detecting house-sized waves during a September 2012 storm.
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Results were recently published recently in Geophysical Research Letters.
"As the Arctic is melting, it's a pretty simple prediction that the additional open water should make waves," said lead author Jim Thomson, an oceanographer with the UW Applied Physics Laboratory.
His data show that winds in mid-September 2012 created waves of 16 feet high during the peak of the storm. He also traced the sources of those big waves.
Arctic ice used to retreat less than 100 miles from the shore. In 2012 however, it retreated over 1,000 miles.
Wind blowing across an expanse of water for a long period of time creates whitecaps and then small waves, which slowly form big swells that carry large amounts of energy.
The size of the waves increases with the travel distance over open water. When waves grow bigger, they also catch more wind, driving them faster and with more energy.
"Almost all of the casualties and losses at sea are because of stormy conditions, and breaking waves are often the culprit," Thomson said. It also could be a new feedback loop leading to more open water as bigger waves break up the remaining summer ice floes.
Waves breaking on the shore could affect the coastlines, where permafrost is already making shores more susceptible to erosion, according to the study.
Observations were made as part of another project by a sensor anchored to the seafloor and sitting more than 150 feet below the surface in the middle of the Beaufort Sea approximately 350 miles off Alaska's north slope.
It measured wave height from mid-August until late October 2012, according to the study.
"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.
Satellite can give an estimate of wave heights, but they don't provide exact numbers for storm events. They also don't work well for the partially ice-covered waters that are common in the Arctic during the summer.
Bigger waves and warming temperatures could act together on summer ice floes, Thomson said.
"At this point, we don't really know relative importance of these processes in future scenarios," he added.
Figuring out the relationship could help predict what will happen to the sea ice in the future and help forecast how long the ice-free channel will remain open each year.
For the recent paper, Thomson only discussed waves at one place. This summer, Thomson is part of an international group led by the UW that has plans to put dozens of sensors in the Arctic Ocean to learn more about the physics of the sea-ice retreat.
"There are several competing theories for what happens when the waves approach and get in to the ice," Thomson said. "A big part of what we're doing with this program is evaluating those models."
Thomson will be out on Alaska's northern coast from late July through mid-August, deploying sensors to track waves.
He is hoping to learn more about wave heights and how they are affected by ice conditions, the weather, and the mount of open water.
"It's going to be a quantum leap in terms of the number of observations, the level of detail and the level of precision" for measuring Arctic Ocean waves, Thomson said.