By and large, the most significant physical force experienced by the animals and plants that live along the shore are wind-generated ocean waves. Storms over the open ocean often generate waves that reach and exceed heights of 10 to 15 meters. As these waves cross the expanse of the ocean, the energy carried within the waves is eventually delivered to the coast, where they break on the beaches and rocky shoreline, such as those surrounding the Hopkins Marine Station. It is here that the waves expend their energy, washing over the intertidal animals and plants and slowly scraping out the natural weaknesses of the rocks to form our local tidepools. As one can imagine the wave forces that pound these beaches and rocky shoreline can have a significant influence on structuring of the ecology of intertidal and subtidal communities.
Periodically installed offshore of Hopkins Marine Station is a bottom-mounted wave gauge instrument (SeaBird SBE26) that provides measurements of both temperature and significant wave height mutliple times per day. What is meant by the term "significant wave height?"
Significant wave height is a common index of sea state, and is determined by average height of the highest one third of waves (Kinsman 1965). The average of the highest third of the measured waves is "significant" in the sense of having ignored the smallest waves in calculating the average, and focusing instead only on those that have the greatest energies. Many measurements of waves under a variety of conditions have shown that the maximum height of the waves is on the order of l.5 to 2.0 times greater than the significant wave height. When one hears the U. S. Coast Guard predictions of wave conditions, it generally is the significant wave height that is being reported. Consequently, those waves that we experience on shore can potentially be twice as high as the predication provided (Komar, 2007).
Wave Buoy Data from January 2009
This buoy was pulled from the water at the end of February 2009 and has been subplanted by the Cabrillo Point Buoy.
Komar, P. D. 2007. Encyclopedia of tidepools & rocky shores. Denny M.W. and Gaines S.D. Eds. University of California Press.