Maximum height of extreme waves up dramatically in Pacific Northwest
A new assessment concludes that the highest waves in a “100-year event” along the Pacific Northwest’s coast may be as much as 46 feet, up from estimates of only 33 feet that were made as recently as 1996, and a 40 percent increase; the new findings raise special concerns for flooding, coastal erosion, and structural damage; “The Pacific Northwest has one of the strongest wave climates in the world, and the data clearly show that it’s getting even bigger,” says one of scientists involved
The Oregon coast // Source: www.sciencedaily.com
A major increase in maximum ocean wave heights off the Pacific Northwest in recent decades has forced scientists to re-evaluate how high a “100-year event” might be, and the new findings raise special concerns for flooding, coastal erosion, and structural damage.
The new assessment concludes that the highest waves may be as much as 46 feet, up from estimates of only 33 feet that were made as recently as 1996, and a 40 percent increase. December and January are the months such waves are most likely to occur, although summer waves are also significantly higher.
In a study just published online in the journal Coastal Engineering, scientists from Oregon State University and the Oregon Department of Geology and Mineral Industries report that the cause of these dramatically higher waves is not completely certain, but “likely due to Earth’s changing climate.”
Using more sophisticated techniques that account for the “non-stationarity” in the wave height record, researchers say the 100-year wave height could actually exceed 55 feet, with impacts that would dwarf those expected from sea level rise in coming decades. Increased coastal erosion, flooding, damage to ocean or coastal structures and changing shorelines are all possible, scientists say.
“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,” said Peter Ruggiero, an assistant professor in the OSU Department of Geosciences. “The Pacific Northwest has one of the strongest wave climates in the world, and the data clearly show that it’s getting even bigger.
“Possible causes might be changes in storm tracks, higher winds, more intense winter storms, or other factors,” Ruggiero said. “These probably are related to global warming, but could also be involved with periodic climate fluctuations such as the Pacific Decadal Oscillation, and our wave records are sufficiently short that we can’t be certain yet. But what is clear is the waves are getting larger.”
In the early 1990s, Ruggiero said, a fairly typical winter might have an offshore wave maximum of a little more than 25 feet. It was believed then — based primarily on data from two offshore buoys — that 10 meters, or 33 feet, would be about as large as waves would ever get, even in a massive “100-year” storm. Then a major El Nino — which tends to bring larger waves, higher water levels and increased erosion — happened in 1997-98 and led to
