Academic journal article The Geographical Review

Meteorological Tsunamis in Southern Britain: An Historical Review

Academic journal article The Geographical Review

Meteorological Tsunamis in Southern Britain: An Historical Review

Article excerpt

Meteorological tsunamis, or meteo-tsunamis, are waves that possess tsunami characteristics but have a meteorological origin (Defant 1961; Rabinovich and Monserrat 1996, 1998; Bryant 2001; Gonzalez, Farreras, and Ochoa 2001). Tsunamis are characterized by their long wavelength and long-period nature; that is, the distance and time, respectively, between consecutive wave crests, often measured in kilometers and tens of minutes rather than in meters and seconds, as with most wind-generated waves, characteristics that enable shoaling tsunamis to grow in height at the shore and to penetrate relatively far inland. Various local names around the world describe meteorological tsunamis, such as rissaga in the Spain's Balearic Islands (Monserrat, Ibbetson, and Thorpe 1991), abiki in Japan's Nagasaki Bay (Hibiya and Kajiura 1982), marrobbio in Sicily (Candela and others 1999), Seebar in the Baltic Sea, and also, perhaps, "freak waves" (White and Fornberg 1998; Wu and Yao 2004).

Meteo-tsunamis have the same periods, spatial scales, physical properties, and destructive impacts as seismically generated tsunamis have when they refract and shoal along coasts (Bryant 2001; Monserrat, Vilibi, and Rabinovich 2006). Rogue waves are large meteorological waves that are infamous for sinking ships in the open sea and thus differ from tsunamis, which are of low amplitude in the open ocean, but rogue waves formed in coastal waters may be considered meteo-tsunamis if they take on tsunami-like characteristics (Kharif and Pelinovsky 2003).

A number of mechanisms can result in a meteo-tsunami. These include the passage of cyclones or hurricanes, frontal squalls, atmospheric pressure jumps (sudden changes in atmospheric pressure associated with thunderstorms), atmospheric gravity waves (vertical oscillations of air cells), tide-generated internal waves (Giese and others 1982), wave superposition (addition of overlapping wave-crest heights), interaction of wind and current, and atmospheric shock waves from volcanic activity (Rabinovich and Monserrat 1996; Lowe and de Lange 2000; Bryant 2001). These processes can generate tsunami-like waves if the disturbance propagates at the same speed as any surface ocean wave being generated (Monserrat, Vilibi, and Rabinovich 2006). Meteo-tsunamis are also very sensitive to resonance generated by local coastal geometry and topography, which, in enclosed inlets, bays, and harbors, can induce high-amplitude seiches; that is, standing waves that slosh back and forth across enclosed water bodies (Rabinovich and Stephenson 2004).

Coastal managers do not currently consider the coast of the British Isles to be at risk from meteo-tsunamis, but a review of historical large waves in southern Britain leads us to believe that the phenomenon does occur. This is particularly so within the enclosed basins of the Bristol Channel and the English Channel, sometimes with catastrophic consequences (Figure 1). Some authors have criticized the current coastal hazard planning in the United Kingdom for its lack of integration: It operates at the local or regional level and is usually conducted by local government authorities (Ballinger and others 2000). Coastal planners in the United Kingdom are more concerned with long-term, predictable hazards, such as coastal flooding, erosion, and sea-level rise, than with meteo-tsunamis, but evidence suggests that meteo-tsunamis should also be included in any coastal hazard assessment of these areas.

[FIGURE 1 OMITTED]

METEO-TSUNAMI OCCURRENCES

Events included in this study share a key trait: one or more large waves that resemble a tsunami with no known associated seismic activity but with a possible meteorological explanation. However, the possibility exists, even with a meteoro-logical explanation, that some of these events may be due to distant seismic activity or a submarine landslide. The locations of places mentioned in this article are shown in Figure 2, and Table I summarizes the characteristics of meteo-tsunamis they experienced. …

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