Extreme Ocean Storms Increasing with Global Warming

Photo: NOAA

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Support for the idea that global warming is increasing the frequency of extreme ocean storms has come from an unlikely place: the seismographs employed to measure earthquakes around the world.

But seismographs deep inland are sensitive enough to detect "microseisms" that result from ocean waves lapping at the shores at the edges of the continent. Dismissed as "background noise" in the more important enterprise of detecting deadly earthquakes, these "microsesisms" actually reveal changes in wave patterns that scientists have used to assess the frequency of large storms at sea.

The new research was presented by Richard Aster, a geophysics professor at the New Mexico Institute of Mining and Technology, at the annual meeting of the Seismological Society of America.

Here's how the society described the research:

"As storm winds drive ocean waves higher, the microseism signals increase their amplitude as well, offering a unique way to track storm intensities across seasons, over time, and at different geographical locations. For instance, Aster and colleagues Daniel McNamara from the U.S. Geological Survey and Peter Bromirski of the Scripps Institution of Oceanography recently published analysis in the Seismological Society of America journal Seismological Research Letters showing that microseism data collected around the Pacific Basin and throughout the world could be used to detect and quantify wave activity from multi-year events such as the El Niño and La Niña ocean disruptions.

The findings spurred them to look for a microseism signal that would reveal whether extreme storms were becoming more common in a warming world. In fact, they saw 'a remarkable thing,' among the worldwide microseism data collected from 1972 to 2008, Aster recalled. In 22 of the 22 stations included in the study, the number of extreme storm events had increased over time, they found.

While the work on evaluating changes in extreme storms is 'still very much in its early stages,' Aster is 'hoping that the study will offer a much more global look' at the effects of climate change on extreme storms and the wind-driven waves that they produce. At the moment, most of the evidence linking the two comes from studies of hurricane intensity and shoreline erosion in specific regions such as the Pacific Northwest Gulf of Mexico, he noted.

The researchers are also working on recovering and digitizing older microseism records, potentially creating a data set that stretches back to the 1930s. Aster praised the work of the long-term observatories that have collected the records, calling them a good example of the 'Cinderella science' — unloved and overlooked — that often support significant discoveries.

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