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The tides, they are a-changin'
Author: Kathryn Kirkland; photo by Kelly James
Posted: June 1, 2009

David Jay, engineerng professorTIDES ARE GETTING BIGGER along the West Coast and global climate change is the likely culprit.

Engineering Prof. David Jay says the amplitude of tides from Alaska to Mexico has increased, meaning the change between the highest and lowest tides is bigger. Though the rise in global sea levels is well documented, the tides themselves were, until now, thought to be constant.

Jay came upon the tidal change almost by accident. He was training a high school student in how to run a tidal analysis program when the student's results indicated an increase in tidal amplitude near Astoria. Jay had him recheck his work, and then suggested analyzing data from a San Francisco site. There, too, tidal amplitude was increasing. That began a five-year project to collect and analyze historic tidal readings along the West Coast. Study findings were published in a Geophysics Research Letters article early this year.

The growth in tidal amplitudes may accelerate coastal erosion, says Jay, especially in areas along the Oregon coast where the sea level is rising and storm waves are growing larger. Tides also play an important role in oceanic processes related to healthy ecosystems, but the role larger tides may play in these complex processes, and what effect the increased tides may have on nutrient supplies and fisheries, requires further study.