Tsunami Ionospheric Monitoring Across the Pacific Ocean and the Southern Atlantic

<p><span>As tsunamis propagate across open oceans, they remain largely unseen due to the lack of</span><br><span>adequate sensors. To help better mitigate the tsunami risk, we use a detection method that takes</span><br><span>advantage of the efficient coupling of tsunami waves with the atmosphere. Tsunami-induced</span><br><span>internal gravity waves thus travel upward in the atmosphere, where amplitude amplifies by several</span><br><span>orders of magnitude as the air density decreases with altitude. Once the waves reach the</span><br><span>ionosphere, they put charged particles into motion, creating propagative phenomena known as</span><br><span>Traveling Ionospheric Disturbances (TIDs). Thanks to the Global Navigation Satellites Systems</span><br><span>(GNSS), such disturbances can be monitored and observed using the Total Electron Content (TEC)</span><br><span>derived from the delay that the ionosphere imposes in the electromagnetic signals transmitted to</span><br><span>the Earth’s surface by the GNSS satellites. Here we show ionospheric TEC signatures following the</span><br><span>passage of three ocean-wide tsunami events: the two tsunamis triggered by the March 4th, 2021</span><br><span>8.1 Mw Kermadec Islands, New Zealand, and the July 29th, 2021 8.2 Mw Perryville, Alaska</span><br><span>earthquakes, as well as across the southern Atlantic following the tsunami generated by the</span><br><span>August 12th, 2021 8.1 Mw Sandwich Islands earthquake. We classify the observed TEC signatures</span><br><span>based on detection reliability and the potential connection to the tsunami wavefield. In addition,</span><br><span>we utilize an analytical model to investigate the source of these identified TEC signatures. Thus, we</span><br><span>ensure their gravity-waves origin and assess the characteristics (wavelength, period, etc.) of such</span><br><span>gravity waves, which is necessary to confirm they originate from the tsunami. Finally, to better</span><br><span>map the tsunami amplitude at the ocean level in various configurations, we examine, compare,</span><br><span>and contrast the amplitude of the identified tsunami-induced TEC signatures from geographically</span><br><span>sparse regions. We account for multiple parameters such as the local magnetic field, the azimuth,</span><br><span>and the distance to the tsunami source. They all affect the TEC signature detection and the</span><br><span>retrieval of the tsunami wavefield and, thus, potentially, the estimated risk.</span></p>