November 28, 2016
By Marie Zhuikov
A team led by University of Wisconsin-Madison researchers has found that small, one-foot, tsunamis caused by thunderstorms (meteotsunamis) happen more than 100 times per year on the Great Lakes. Also, larger meteotsunamis of nearly three feet occur once per year on average.
The team headed by Adam Bechle, J. Phillip Keillor Fellow with the Wisconsin Coastal Management Program and Wisconsin Sea Grant, and Chin Wu, UW-Madison professor of civil and environmental engineering, analyzed 20 years of data from 32 water-level stations on the U.S. side of the Great Lakes. Most meteotsunamis occur in late spring to early summer, coinciding with the beginning of the recreational season on the lakes. Most occur in the southwest part of the Great Lakes, with Lake Michigan having the most and lakes Ontario and Superior having the least. The results were published in the Nov. 24 issue of Scientific Reports.
The timing of most meteotsunamis is cause for concern. “Because it coincides with the beginning of summer swimming and recreation, this puts many lake users at risk,” said Bechle. “These findings indicate that meteotsunamis have been an underrated hazard for the Great Lakes region.
“In the past, we tended to only think of meteotsunamis as being large and destructive events that were six feet high and washed dozens of people off shore,” said Bechle. “We thought of them as rare. And it’s true – events of that magnitude are quite rare. But with this study, we wanted to get a picture of the more moderately sized events. A one-foot water level change over a short time period can be dangerous for coastal infrastructure and can cause coastal bluff erosion, dangerous rip currents and nearshore sediment transport.”
Often mistaken for seiches (another type of wave), meteotsunamis are single waves similar to, but smaller than, tsunamis caused by earthquakes or landslides. Instead of being caused by seismic activity, meteotsunamis are formed by strong storms that move over the water.
Notable meteotsunamis happened recently in 2012, when three swimmers were rescued after being swept offshore into Lake Erie near Cleveland, and in 2014, when a Lake Superior meteotsunami overtopped the Soo Locks, interrupting shipping operations and prompting homes to be evacuated in Sault Ste. Marie, Ontario.
The researchers, who looked at meteotsuamnis in Lake Michigan previously, wanted a larger perspective on when and where they were happening in the Great Lakes with this project. They analyzed water level measurements taken from 1994 to 2015. Although they didn’t notice any trends in meteotsunami frequency during that time span, they did see peaks in the number of meteotsunamis during 2000 and 2011. Lower meteotsunami activity occurred during 2005 through 2007.
“That may mean there’s some sort of oscillation going on possibly,” Bechle said. “We still need to look at things like El Nino or other sorts of interannual weather patterns to see if there’s some sort of a tie-in with climatic variables.”
The team also looked at what future climate conditions might hold for meteotsunamis. Larger meteotsunamis tend to be associated with convective thunderstorms, and more such storms are projected for the Great Lakes. “It’s not a strong tie-in, but it’s logical to think that if the potential for convective thunderstorms increases, then meteotsunamis might be more frequent as well,” Bechle said.
Currently, Alvaro Linares, a UW-Madison Ph.D. student, is developing a meteotsunami wave height prediction model that is tailored by geography and fed by weather data like wind strength and barometric pressure. The model can provide real-time meteotsunami warnings to help mitigate the threat to property and life on the Great Lakes.
In addition to researchers at UW-Madison, the team includes David Kristovich, University of Illinois at Urbana-Champaign; Eric Anderson, NOAA’s Great Lakes Environmental Research Laboratory; David Schwab, University of Michigan; and Alexander Rabinovich, Russian Academy of Sciences in Moscow.
Funding for the project came from Wisconsin Sea Grant, the National Science Foundation, the Cooperative Institute for Limnology and Ecosystems Research Long-term Great Lakes Fellowship, NOAA-Coastal Storms Program, the UW-Madison/UW-Milwaukee Intercampus Research Incentive Grants Program, the University of Illinois, and the Russia Foundation for Basic Research Grants.