A meteotsunami in the north Indian Ocean triggered by Hunga Tonga volcanic eruption.

The Hunga Tonga Volcano in the southwest Pacific islands of Tonga erupted in January 2022. The massive explosion resulted in the generation of Lamb waves that propagated globally with a speed of ~ 300m/s and generated a tsunami that has affected numerous Pacific countries. In this study, we use observations and a numerical model to show the impact of this volcanic eruption on the Indian coastline. The Lamb wave took roughly 10 to 11 hours to reach the Indian coast, as observed in atmospheric pressure at mean sea level. Further, the signatures of high-frequency sea-level perturbations were observed from coastal tide-gauge networks along the Indian coastline. Our analysis shows that sea-level oscillations with considerable amplitude (10-20 cm) were observed along the Indian coastline during this period. The predominant frequency and amplitude, and oscillation were different at different locations. Further, an asymmetry between east and west coast stations was observed in the nature of high-frequency oscillations forced by the Hunga Tonga volcanic eruption. Finally, a numerical model was utilised to demonstrate how topography contributes to the observed sea-level disturbances. The model simulations imply that bathymetry is crucial to the observed sea-level variability. Thus, a 12000 km away event has significantly impacted the sea level along the Indian coastline. This work paves the way for understanding the importance of high-frequency variabilities along the Indian coastline and discusses the necessity to enhance the capability of our early warning systems by incorporating these variabilities.