Image credit: Erica Harris, Oregon State University/Flickr
The height of extreme waves, commonly called "100-year waves," is increasing in the Pacific Northwest. According to new research from Oregon State University, the height of these giant waves could be more than 40 percent greater—reaching more than 46 feet—than previous estimates. The devastation to the coast such waves would cause, according to researchers, could be even greater than a rise in sea levels.Peter Ruggiero, an assistant professor in the OSU Department of Geosciences, explained:
The rates of erosion and frequency of coastal flooding have increased over the last couple of decades and will almost certainly increase in the future...the Pacific Northwest has one of the strongest wave climates in the world, and the data clearly show that it's getting even bigger.
Already, rising wave heights have had "double or triple the impact" of sea-level rises in terms of erosion, flooding, and damage.
Only Once Every Hundred Years?
The popular term "100-year waves," based on the traditionally-perceived frequency of the event, is a misnomer. In fact, extreme waves—also called rogue waves, freak waves, monster waves, and killer waves—can occur at any time and, depending on the ocean and weather conditions, can occur repeatedly in a short period of time.
One such period was the 1997-1998 El Nino during which a string of extreme waves exceeding 33 feet—then thought to be the maximum rogue wave height—shattered previous records and perceptions of what was possible.
The Mechanics of an Extreme Wave
Extreme waves are not tsunamis, caused by deep-sea geologic events, nor are they tides, which are caused by the gravitational pull of the sun and the moon. Instead, extreme waves are wind waves—generated by the movement of air across the surface of the water.
In the ocean, surface waves generated by wind can travel thousands of miles beyond their origin—long after the wind has stopped. The size and frequency of these waves is influenced by wind speed, the distance air has traveled across the surface, the width of the area affected, and the depth of the water. Clashing currents can magnify the size of wind waves, sometimes leading to the formation of an extreme wave.
Why are Waves Getting Bigger?
Due to a lack of historical data, it's difficult to determine the exact reason waves in the Pacific Northwest are getting bigger. Still, Dr. Ruggiero commented that:
Possible causes might be changes in storm tracks, higher winds, more intense winter storms, or other factors...these probably are related to global warming.
He added that they could also be the result of periodic fluctuations in the climate, like those caused by the Pacific Decadal Oscillation.
Regardless of the cause, waves are getting bigger and the impact they are having on coastal communities is real. It's expected that future rises in sea levels and an expected drop in coastal elevation caused by a subduction zone earthquake will only worsen the impact these extreme waves have on the coasts of northern Oregon and Washington states.