The 2022 Tonga tsunami in the marginal seas of the northwestern Pacific Ocean

The Hunga Tonga volcanic eruption on 15 January 2022 created a tsunami affecting the entire Pacific Ocean. The observed tsunami was found to have a dual mechanism and was caused both by the wave incoming from the source area and by an atmospheric wave propagating with the speed of sound. The tsunami was clearly recorded in the marginal seas of the northwestern Pacific, including the Sea of Japan, the Sea of Okhotsk and the Bering Sea, in particular on the coasts of Kamchatka, the Kuril Islands and the Aleutian Islands. We examined high-resolution records (1-min sampling) of about 50 tide gauges and 15 air pressure stations in these seas for the period of 14-17 January 2022. On the Russian coast, the highest wave with a trough-to-crest wave height of 1.4 m was recorded at Vodopadnaya, on the southeastern Kamchatka Peninsula; on the coasts of the Aleutian Islands the tsunami waves were even higher, up to 2 m. Based on numerical modelling we estimated the arrival time of the gravitational tsunami waves from the source. We revealed that the character of sea level oscillations for most of the stations evidently changed before these waves arrived. A comparative analysis of sea level and atmospheric data indicated that these changes were probably caused by the atmospheric waves generated by the volcanic eruption.