We are living through a megacycle of ‘tsunamis’ and storms in the Mediterranean

Friday, 13 October 2017, 05:30:51 PM. As frightening as they are, real tsunamis do much less damage than storms—and they may be less common than scientists realized.

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While tsunamis and storms are very different events, they look surprisingly similar in the geologic records scientists rely on for a long-term understanding of their frequency. According to a paper published Wednesday in the journal Science Advances, that has allowed a huge number of storms to masquerade as tsunamis, and it could be warping our sense of the risks we face.

“Much of the scientific literature, at least in the Mediterranean, has focused on the impact of ancient tsunamis, particularly in the wake of recent events in the Indian Ocean and Japan,” lead author Nick Marriner, a geologist at the French National Center for Scientific Research, told Newsweek in an email. “Generally speaking, storms have solicited much less interest.”

we-are-living-through-a-megacycle-of-tsunamis-and-storms-in-the-mediterranean photo 1 The Mediterranean on a calm day, as seen from Sardinia. Most of the alleged tsunamis scientists examined occurred in Italy or Greece, with a couple in the Straits of Gibraltar and a handful in the eastern Mediterranean. N. Marriner

But Marriner and his co-authors argue that about 90 percent of events over the past 4,500 years that have been interpreted as tsunamis were actually storms. If they’re correct, that means risk managers and the public should be thinking much more carefully about storms.

One of the complications is that it would make sense for the Mediterranean to have a problem with tsunamis, given its boundaries between the African, Arabian and Eurasian geologic plates and the Anatolian microplate that squeezes between them beneath Turkey and the eastern Mediterranean. All those plates rubbing against each other could spur the earthquakes that create tsunamis.

So, particularly in the wake of the deadly tsunamis in Indonesia in 2004 and Japan in 2011, researchers have been dedicating more time to trying to understand the risk of similar events in the Mediterranean. In order to get more data, scientists have sought to gather databases of past tsunamis in the region.

Marriner and his colleagues revisited 135 incidents, focusing on those that had been identified solely through geology and ignoring events for which we have written descriptions. Most of the alleged tsunamis they examined occurred in Italy or Greece, with a couple in the Straits of Gibraltar and a handful in the eastern Mediterranean.

In an odd twist, they found that these events came in cycles of about 1,500 years. Even more notable, that timeline lined up well with cool periods in the climate cycle like the one dubbed the Little Ice Age, from about 1300 to 1850. That’s an eyebrow-raising coincidence, since certain weather patterns can cause what’s known as meteotsunamis, which act kind of like tsunamis but are caused by weather patterns, not earthquakes, and affect smaller geographic regions.

we-are-living-through-a-megacycle-of-tsunamis-and-storms-in-the-mediterranean photo 2 These boulders are the sort of evidence geologists use to identify past tsunamis and storms. C. Morhange

Marriner now believes many of the Mediterranean events that occurred during these cool periods and that scientists have spotted only through geologic cues like boulders carried inland were storms disguised as tsunamis. But that isn’t good news: As terrifying as tsunamis are, Marriner calculates storm events have killed four times as many people and caused four times as much damage since 1900.

“It is imperative not to lose sight of the risks posed by storm events, as we have seen along the southeastern seaboard of the U.S. and the Caribbean in recent months,” Marriner wrote.

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