Meteorological tsunamis on the Pacific coast of North America Fine I.V..1,2, Thomson R.E.1 , Rabinovich A.B.1,3 1 Institute of Ocean Sciences, Sidney, Canada 2 Heat and Mass Transfer Institute, Minsk, Belarus 3 Shirshov Institute of Oceanology, Moscow, Russia

Contents 1. Introduction: Tsunamis and meteotsunamis 2. Observations: - 9 December 2005 - 13 July 2007 - 26 February 2008 3. Model: Energetic of the wave generation, major mechanisms and effects 4. Conclusions

“Rissaga” waves in Ciutadella Harbour (Menorca I.) 15 June 2006 More than 40 damaged boats. Total loss: ~ 30 mln euros. (Montserrat, Vilibic, and Rabinovich, 2006)

Vela Luka, Croatia, 21 June 1978

Observational sites on the coast of British Columbia and Washington State Tofino Pat. Bay Bamfield Victoria Neah Bay La Push Seattle Tacoma Longview

Tsunami-like event recorded on 9 December 2009 on the coast of British Columbia There were no seismic activity nor strong storm in the region.

Later we found an atmospheric pressure record at La Push showing that the event was forced by an abrupt jump of atmospheric pressure (~2 mb).

Tsunami-like event on 13 July 2007 recorded at tide gages of the WA and BC coast in the Golf area. Sea level All records have a clear arrival time.

Tsunami-like event on 13 July 2007 recorded at tide gages of the WA and BC coast in the Golf area. Sea level Atmospheric pressure All records have a clear arrival time. Atmosphreric disturbances were on nigth time of 13 July and repeated on 15 July 15 with less intersity.

We analyzed atmospheric pressure records and found the event was forced by disturbance moving northward with speed about 23 m/s

Additional high resolution microbarograph records in the Greater Victoria Area confirmed the previous estimates.

Comparison of the tide gauge record at Patricia Bay and atmospheric pressure record at the nearby microbarograph station. Sea level and atmospheric variations started almost simultaneously

The direction and the speed of the moving atmospheric disturbances are in good agreement with the direction and speed of the jet stream in the area of interest.

Tsunami-like event on 26 February 2008 recorded at tide gages of the WA and BC coast in the Golf area.

The direction (toward east-north) and the speed (~30 m/s) of the moving atmospheric disturbances are also in good agreement with direction and speed of the jet stream in the area of interest.

Model Similarly to a seismological tsunami, a meteotsunami is forced by a term in the mass conservation equation

Energy generation Wave energy is generated due to the hysteresis effect. In a stationary case, when the atmospheric disturbance moves with a constant velocity, the wave energy is not generated. However, in a non-stationary case the energy is generated permanently feeding propagating waves.

Proudman resonance

central part of the area Bathymetry map of the central part of the area “Supersonic” (red) and “subsonic” (blue) areas for U=30 m/s

The areas of the active energy generation Meteotsunami modelling: The disturbance moves to the north 20 m/s 30 m/s

Simulated records at specific locations

The simulated energy as function of atmospheric parameters The total generated energy (over the entire region) is nearly isotropic. The atmospheric speed is the major factor

Conclusions 1. Meteotsunamis are relatively frequent phenomena on the west coast of the US and Canada. 2.Meteotsunami in the area are mainly caused by fast moving (20 – 30 m/s) atmospheric disturbances of 1-3 mb with periods of ~5 min – 2 hrs. 3. High atmospheric activity (small-scale disturbances and buoyancy waves) may last hours and even days. The speed and direction of the disturbances correlate well with the speed and direction of the atmospheric jet stream. 4. Mountains and instability conditions (occurring mainly the night time in summer) are additional important factors stimulating the process.

5. The efficiency of the wave energy generation is related to the Proudman resonance; with the atmospheric disturbance speed of 20-30 m/s most of energy is generated at depths of 40-90 m. 6. The direction and peak period of the atmospheric disturbance propagation are the secondary factors influencing the total amount of energy generated in the area. For some sites these factors can play the crucial role.

Thank you!