Mesospheric pressure source from the 2022 Hunga, Tonga eruption excites 3.6-mHz air-sea coupled waves.

Abstract

Lamb waves and meteotsunamis generated by the Tonga volcanic eruption in 2022 were observed worldwide. Here, we show a distinct spectral peak at approximately 3.6 millihertz in the air and seafloor pressures of those waves. The peak in the air pressure represents resonant coupling between Lamb and thermospheric gravity waves. To reproduce the observed spectral structure up to 4 millihertz, an upward-moving pressure source with a duration of 1500 seconds should be placed at altitudes of 58 to 70 kilometers, which are slightly higher than the overshooting plume top of 50 to 57 kilometers. The high-frequency meteotsunamis forced by the coupled wave are further amplified by near resonance with the tsunami mode upon their passage through the deep Japan Trench. From the spectral structure of broadband Lamb waves including the 3.6-millihertz peak, we suggest that the pressure sources for generating the Pacific-scale air-sea disturbances are in the mesosphere.