Monday, May 9, 2011

Pacific Decadal Oscillation, Local Sea Level and Slope Stability

Sea level rise is to be expected as global warming proceeds and glaciers melt. But linking sea level rise directly to how much glacial ice melts is not so simple. It is complicated by a variety of other factors that must be considered. Stuff like thermal expansion of water, isostatic response of the earth surface as mass (water) is moved around, and local variability based on tides and wind trends.

Weather patterns in the Pacific Ocean over the past decade have suppressed local sea level HERE, but that may change if we move into a cooler Pacific Decadal Oscillation (PDO) period. The chart above shows that over the long term sea level has been rising at San Francisco, but in the last decade actually reversed to to weather patterns.

With wind patterns shifting the west coast will go through a bit of a catch up phase. What this might mean for Washington State and for my work in assessing slope stability is that the frequency of erosive shoreline events along Puget Sound and Salish Sea shoreline bluffs will likely increase causing a greater frequency in shoreline erosion induced landslides. Shifting weather patterns may cause greater frequency of intense storms Bromirski, Flick and Caya (2002).

The PDO cool phase appears to have some impact on overall global temperature and is modeled by climate folks as such. However, the temporary cooling effect is overwhelmed by the CO2 forcing. If anything, a cooler PDO may be masking global warming impacts.

Berini (2010) 

Berini (2010)

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