Tsunami waves observed by Swot for the second time

Swot (Surface Water and Ocean Topography) the French-U.S. Swot satellite, launched in December 2022, has started its third year of operations with a continuing harvest of discoveries. Two years after the first 2D picture of a tsunami in the Southwest Pacific Ocean [Faugère et al., 2024], members of an international science collaboration from SRP (Universidad de Chile), Cnes/CLS, UniCA/OCA/CNRS/IRD/Géoazur, CEA (France) and GNS Science (New-Zealand) have caught new tsunami wave features in the South Atlantic Ocean on May 2, 2025, combining the unprecedented resolution and accuracy of the KaRIn instrument and tsunami predictions (see figures 1 and 2). The satellite sea-surface elevation observation and the tsunami simulation at 17:51:29 UTC (see video) show clear and similar wave-like patterns and planar wave fronts. This tsunami was initiated about 5 hours earlier offshore the southernmost part of Chilean Patagonia by a rare earthquake showing an estimated moment magnitude Mw7.4. Because of uncertainty on the source, lack of deep-sea water level measurements (i.e., DART systems) and to prevent a potentially severe impact on the coastal populations, the Hydrographic Service of Chilean Navy issued an evacuation alert in South of Chile and Antarctica and cancelled it a couple hours later.

The earthquake took place a hundred kilometers south of the mythic Cape Horn, within the Drake Passage. In this remote part of the globe, well-known to navigators, seismic and tsunami in-situ measurements remain severely sparse. By analyzing the novel Swot dataset, tsunami scientists hope to shed new light on the complex source processes that triggered the tsunami. Swot could help better understand the tectonic peculiarities of a poorly known tectonic zone located at the junction between the Antarctica-Scotia plate boundary and the Shackleton fracture zone.

References:

• Faugère, Y., Roger, J., Delepoulle, A., Dibarboure, G., and Hebert, H.: The 19 May 2023 tsunami near the Loyalty Islands captured by the new Swot satellite, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15140, https://doi.org/10.5194/egusphere-egu24-15140, 2024.
• Unsmoothed L3_LR_SSH: "The Swot L3_LR_SSH product, derived from the L2 Swot KaRIn low rate ocean data products (NASA/JPL and CNES), is produced and made freely available by DUACS and AVISO teams as part of the DESMOS Science Team project". DUACS/AVISO, 2024. Swot Level-3 KaRIn Low Rate SSH Unsmoothed (v2.0.1) [Data set]. CNES. https://doi.org/10.24400/527896/A01-2024.003