Oregon State University researchers, joined by scientists from the Oregon Department of Geology, say the wave height increase is forcing a re-evaluation of how high a "100-year event" might be, and the new findings raise special concerns for flooding, coastal erosion and structural damage.
The study, led by Assistant Professor Peter Ruggiero, concludes the highest waves might be as high as 46 feet, up 40 percent from estimates of only 33 feet made as recently as 1996.
"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," Ruggiero said. "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. 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."
The findings are detailed in the journal Coastal Engineering.