The 2022 Tonga Volcanic Tsunami: Lessons from a Global Event

Abstract. The January 15, 2022, Tonga eruption provides a rare opportunity to understand global tsunami impacts of explosive volcanism, including "air-shock” tsunamis induced by Lamb waves travelling in the atmosphere, and to evaluate future hazards. The propagation of the air-shock and oceanic tsunami components were analyzed using globally distributed 1-min measurements of air pressure and water level (tide gauges and deep-water buoys). Oceanic tsunamis (up to 1.7 m) propagated primarily throughout the Pacific, but air-shock tsunamis arrived first and traveled globally, producing water-level perturbations in the Indian Ocean, the Mediterranean, and the Caribbean. The air-shock induced water level response of most Pacific Rim gauges was amplified, likely related to bathymetric processes. The air-shock repeatedly boosted tsunami wave energy as it circled the planet several times. In some locations, the air-shock was amplified as much as 35X relative to inverse barometer by Proudman resonance and topographic effects. Thus, a large volcanic air-shock (10–30 mb) could cause a 3.5–10 m near-field tsunami that would occur in advance of (usually) larger oceanic tsunami waves, posing an additional hazard to local populations. Present tsunami warning systems do not consider this threat.