Observations of meteorological tsunamis along the south-west Australian coast

Abstract

Tide gauge data were used to identify the occurrence, characteristics, and cause of tsunamis of meteorological origin (termed 'meteotsunamis') along the Western Australian coast. This is the first study to identify meteotsunamis in this region, and the results indicated that they occur frequently. Although meteotsunamis are not catastrophic to the extent of major seismically induced basin-scale events, the wave heights of meteotsunamis examined at some local stations in this study were higher than those recorded through seismic tsunamis. In June 2012, a meteotsunami contributed to an extreme water-level event at Fremantle, which recorded the highest water level in over 115 years. Meteotsunamis (wave heights [0.4 m, when the mean tidal range in the region is *0.5 m) were found to coincide with thunderstorms in summer and the passage of low-pressure systems during winter. Spectral analysis of tide gauge time series records showed that existing continental seiche oscillations (periods between 30 min and 5 h) were enhanced during the meteotsunamis, with a high proportion of energy transferred to the continental shelf oscillation period. Three recent meteotsunami events (22 March 2010, 10 June 2012, and 7 January 2013) two due to summer thunderstorms and one due to a winter frontal system were chosen for detailed analysis. The meteotsunami amplitudes were up to a factor 2 larger than the local tidal range and sometimes contributed up to 85 % of the non-tidal water signal. A single meteorological event was found to generate several meteotsunamis along the coast, up to 500 km apart, as the air pressure disturbance propagated over the continental shelf; however, the topography and local bathymetry of the continental shelf defined the local sea-level resonance characteristics at each location. With the available data (sea level and meteorological), the exact mechanisms for the generation of the meteotsunamis could not be isolated.

Global mapping of nonseismic sea level oscillations at tsunami timescales

“…Still, a number of high-frequency processes that substantially contribute to sea level extremes (such as tsunamis, meteotsunamis, and infragravity waves) cannot be properly assessed using hourly data. The science of tsunamis, due to their global importance and impact, has constantly been at the forefront of sea level research9, while the remainder of the high-frequency sea level signal, which can be defined as consisting of nonseismic sea level oscillations at tsunami timescales (NSLOTT), has been researched only locally10111213. The concept of NSLOTT events refers to all sea level oscillations except tsunamis that appear at periods between a few minutes to a few hours.…”

Northern Adriatic meteorological tsunamis: Assessment of their potential through ocean modeling experiments

“…Predicted meteotsunami heights of ∼70 cm (at Rovinj tide gauge) are practically of the same order of magnitude as tides and storm surges, and may considerably endanger the coastal infrastructure if occurring during high tide (and/or storm surge). Matching of a strong meteotsunami event and a high tide was for example found during a century record‐breaking sea level observations in Freemantle, Western Australia [ Pattiaratchi and Wijeratne , ]. High‐frequency oscillations should therefore be included into any assessment of risk of extreme sea levels in the region.…”

“…Meteorological tsunamis or meteotsunamis are rare, but destructive, tsunami‐like events which unexpectedly hit coastal areas, occasionally causing a widespread damage and even loss of human lives [ Ewing et al ., ; Vučetić et al ., ]. They are strongest in those bays and harbors which have large amplification factors [ Gomis et al ., ; Rabinovich , ], but they can also be high and destructive along the shorelines of wide shelves [ Sallenger et al ., ; Paxton and Sobien , ; Pattiaratchi and Wijeratne , ]. Meteotsunamis are most often generated by rapid air pressure changes (∼2 hPa/5 min) [ Vilibić et al ., ; Thomson et al ., ; Okal et al ., ; Šepić and Vilibić , ] and somewhat less often by intense wind disturbances (>20 m/s) [ de Jong and Battjes , ; Bechle and Wu , ; Šepić and Rabinovich , ].…”

Probabilistic Tsunami Hazard Analysis: Multiple Sources and Global Applications

“…Even moderate meteotsunamis can have damaging impacts on boats and ships in harbors and small embayments (Thomson et al, ). Meteotsunami hazard is increased by additional sources of energy: (1) the wind stress (Bechle & Wu, ; De Jong & Battjes, ; Dragani et al, ; Pellikka et al, ; Whitmore & Knight, ), (2) the local high tide level (Horvath & Vilibic, ), and (3) a higher water level from a storm surge or high mean seasonal sea level (Pattiaratchi & Wijeratne, ).…”