Meteotsunamis in south-Western Australia

Meteorological tsunamis (meteotsunamis) are water level oscillations with periods generally less than 6 hours, that are similar to waves generated by seismic activity ('tsunami waves'), except they have a meteorological origin. In particular, they are generated through multi-resonance phenomena initiated through moving pressure disturbances due to squalls, thunderstorms, frontal passages, and atmospheric gravity waves. In this paper, we examine meteotsunamis generated along south-west Australia over the past decade and indicate that they are regular occurrence in the region. During the summer months, meteotsunamis are generated by thunderstorm activity and during the winter months through the passage of cold fronts. A meteotsunami event due to the passage of a cold front contributed to the highest ever water level recorded at Fremantle in 2012. Similarly an incident where a ship broke moorings inside Fremantle Port and impacted on the railway bridge was attributed to a meteotsunami generated by a cold front in 2014. Analysis of local water level records for 2014 revealed that there were > 30 events which could be classified as meteotsunamis with the majority occurring during the winter months associated with the passage of cold fronts. Time-frequency diagrams indicated that during the passage of a cold front the whole spectrum is energised similar to those observed during seismic tsunamis. The meteotsunami events were related to simultaneous meteorological data, including the magnitude of the pressure jumps, speed and direction. Strong currents are generated due to the rapid water level changes as illustrated by the ship incident at Fremantle Port in 2014.Grant: The meteorological data for this study were obtained from the Australian Government Bureau of Meteorology. We would like to thank Allan Gale and Jay Illingworth (Fremantle Ports), Reena Lowry (Department of Transport, Government of Western Australia) for facilitating the provision of data from Fremantle Port and water level data from Fremantle Boat Harbour and Two Rocks, respectively. The study was partially funded by the Bushfire Natural Hazards Cooperative Research Centre.