Near-Coastal Winter Waves From Microseisms

Long-term coastal wave climate variability cannot be reliably assessed from relatively short duration buoy observations that began about 1980. Microseisms at double the wave frequency (DFM) provide a proxy record of coastal wave activity. Here, we show that winter (November to March) wave activity can be well characterized from near-coastal seismometer DFM observations, although extreme wave events are not consistently well reproduced. Reconstructed mean winter seismic significant wave height,sHs, determined using simultaneous seismic and buoy observations, closely track nearby buoyHsover 1992-2017 winters. Buoy-measured mean winter short-period wave variability in the [0.1, 0.15] Hz band is also well reproduced. Generally lowersHsfor high amplitude events, compared with offshore buoyHs, suggests that DFM generation is closer to the coast where shore-reflected long-period opposing wave components are likely higher. These results indicate that digitized pre-1980 archived analog seismograms at near-coastal seismic stations can reliably characterize long-term wave climate changes and decadal variability.