ITS3.6/SM1.2

The phreatoplinan eruption of the shallow submarine Hunga Volcano Tonga formed global air-pressure waves, regional tsunami and an up to 55 km-high eruption column. Despite its large explosive magnitude, the magma erupted were similar to past compositions, and comprised crystal poor (<8 wt% total; plag>cpx>opx) andesite with ~57-63 wt% silica glass. Low magnitude Surtseyan eruptions in 2009-2015 formed from small pockets of andesite that ascended slowly, resulting in high microphenocryst and microlite contents. Large eruptions, including events in ~AD200 and AD1100 and the 2022 event drew magma rapidly from a ~5-7 km deep mid-crustal reservoir. Rapid decompression and quenching (augmented by magma-water interaction) records the heterogeneity of the reservoir, with mingled glass textures and cryptic mixing of subtly different melts. The 2022 feldspar phenocrysts show more mafic melt inclusion compositions than host glass, clear uniform cores and thin rims evidencing ~1 month-long changes caused by decompression, rise and internal mingling of subtlety different melts. CPX phenocrysts show uniform cores a variety of more mafic and similar melt inclusions to the bulk glass, and thin overgrowth rims reflecting only decompression and mingling. Lithic fragments (<8wt%) include common hydrothermal minerals (sulphides, quartz etc). Without evidence of a mafic trigger, or crystalisation induced overpressures, this extremely violent eruption was triggered by top-down processes that led to rapid exhumation/decompression of magma and very efficient explosive magma-water interaction. This could include any, or all of: flank collapse; hydrothermal seal fracturing and ingress of water into the upper magma system and caldera collapse. Subsequent earthquakes suggest that the crustal magma system was rapidly recharged in the days following the eruption.

How to cite: Cronin, S., Brenna, M., Kula, T., Ukstins, I., Adams, D., Wu, J., Paredes Marino, J., Kilgour, G., Leonard, G., White, J., Barker, S., and Gravley, D.: The 15 January 2022 Hunga eruption, Tonga – first petrographic and geochemical results, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13584, https://doi.org/10.5194/egusphere-egu22-13584, 2022.

The January 2022 eruption of Hunga Volcano, Tonga is likely the most explosive mafic eruption yet documented. It exhibited dynamics of ash plume expansion and atmospheric pressure waves unlike anything seen before. This is remarkable considering that it erupted crystal-poor and microlite-poor andesitic magma (57-63 wt% silica glass). The climactic phase produced an eruptive column of at least 39 km in height, however, the ash volume appears anomalously small for the explosive magnitude. Ash from nine different sites across the Kingdom of Tonga were analyzed for textural and morphological properties and grain size distribution. The tephra comprises light pumice (16%), dark pumice (44%), glassy microlite-rich grains (25%), lithics (7%) and free-crystals (Pl, Cpx, Opx) (8%). Specific gravity of particles range from 0.4 to ~2.5. Secondary electron images show that pumices have a variable vesicularity, from dense glassy blocky particles; glassy particles with isolated vesicles and weakly deformed, thick vesicle walls; and a smaller percentage of microvesicular pumices, coated in finer particles. The general characteristics imply a rapid decompression, fragmentation and chilling. This implies some form of phreatomagmatism but with high-efficiency to generate such a large blast – e.g., via propagation of stress waves and thermal contraction rapidly increasing a magma surface area for interaction. The ash is fine-grained and poorly sorted overall. Less than 20 wt.% of ash particles are >1 mm at 80 km SE of the volcano on the main island of Tongatapu, while 70 km NE of the volcano (Nomuka Island) has finer ash, with only 2% of particles >1 mm. It appears that the dispersion axis for the event was directed toward the E or ESE, across the main population centre of Nuku’alofa on Tongatapu. Of the fine fraction 20 wt.% is < 30 micron, 8 wt.% <10 micron but unusually few particles of very fine range (<0.05 wt.% finer than 1 micron). Variations in the mode and sorting of ash fall at different locations and angles from the vent show that there was potentially complex dispersal of ash from different phases of the 11-hour long eruption, and or different plume heights and fragmentation processes involved. Plume observations suggest at least two different plume levels during main phases of the eruption and the fragmentation mechanisms likely varied from the blast-generating phase and the lesser-explosive phases leading up to and following this.

How to cite: Paredes-Mariño, J., White, J., Dürig, T., Baxter, R., Kula, T., Cronin, S., Ukstins, I., Wu, J., Adams, D., Brenna, M., and Brooks-Clarke, I.: Understanding fragmentation mechanism(s) during the 15 January 2022 Hunga Volcano (Tonga) eruption through particle characteristics, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13587, https://doi.org/10.5194/egusphere-egu22-13587, 2022.

In December 2014, eruptions began from a submarine vent between the islands of Hunga Tonga and Hunga Ha’apai, 65 km north of Tongatapu, Tonga. The “Hungas” represent small NW and NE remnants of the flanks of a larger edifice, with a ~5 km-diameter collapse caldera south of them. The 2014/15 Surtseyan explosive eruptions lasted for 5 weeks, building a 140 m-high tuff ring.

Deposits on Hunga Ha’apai and tephra fall on Tongatapu record two very large magnitude eruptions producing local pyroclastic density currents and tephra falls of >10 cm-thick >65 km away. These likely derive from the central edifice/caldera. The 2022 eruption produced slightly less tephra fall, but an extremely large explosive event, with regional tsunami indicating substantive topographic change.

Here we report the bathymetric details of the caldera as of November 2015. A multibeam sounder (WASSP) was used to mapping the shallow (<250 m) seafloor concentrating on the edges of the Hunga caldera. These results were combined with an aerial survey of the 2015 tuff cone, using a combination of drone photogrammetry and real-time kinematic GPS surveys. The bathymetry reveals that previous historical eruptions, including 1988 and 2009, and likely many other recent unknown produced a series of well-preserved cones around the rim of the caldera. Aside from the raised ground in the northern caldera produced by the 2009 and 2014/15 eruptions, the southern portion is also elevated to within a few m below sea level, with reefs present. During the 2015 visit, uplifted fresh coral showed that inflation was ongoing and that the caldera was likely in the process of resurgence.

Much of Hunga Tonga and the 2014/2015 cone was destroyed in the 2022 eruptions, with Hunga Ha’apai intact, but dropping vertically by ~10-15 m. The violence of the 2022 eruption was likely augmented by either caldera collapse or flank collapse from the upper edifice, rapidly unroofing the andesitic magma system and enabling efficient water ingress.

This data provides an essential base layer for assessing changes on the ocean floor, especially to determine any caldera or upper-flank changes. Understanding these changes is crucial for future forecasting future volcanic hazards at Hunga and other nearby large submarine volcanoes.

How to cite: Stern, S., Cronin, S., Ribo, M., Barker, S., Brenna, M., Smith, I. E. M., Ford, M., Kula, T., and Vaiomounga, R.: Post-2015 caldera morphology of the Hunga Tonga-Hunga Ha’apai caldera, Tonga, through drone photogrammetry and summit area bathymetry, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13586, https://doi.org/10.5194/egusphere-egu22-13586, 2022.

The Hunga-Tonga eruption culminated on January 15, 2022, with a high-intensity Plinian eruption exceeding 20 km height, tsunamis affecting local islands and the circumpacific region, locally air-coupled seismic surface waves recorded at teleseismic distances, and explosive shock waves that repeatedly travelled around the world. Hunga-Tonga is a flat-topped volcano that rises about 1700 m above the seafloor, hosting a submarine 3-4 km diameter caldera floor that lies at less than 200 m water depth and is surrounded by an elevated, approx. 100-200 m high caldera wall. Only small parts of the volcano are rising at the caldera wall above the sea level, such as the islands Hunga Tonga Hunga Ha'apai in the north and small unnamed rocks in the south. Satellite imagery acquired by Pleiades and Sentinel 1A suggests that during the January 15, 2022 eruption, the central part of the Hunga Tonga Hunga Ha'apai as well as the small rocks in the south disappeared. By analysing satellite radar and imagery, we constrain island perimeters and morphologies before and after the eruption, to find evidence for island subsidence and erosion. In addition, seismic data recorded during the January 15, 2022 eruption was analysed in the time and frequency domains, revealing high amplitude activity over ~1 hr. The comparison of seismic, GNSS and local tsunami recordings gives insights into the time-succession of the eruption. For instance, moment tensor inversion suggests that the largest amplitude seismic signal was produced by a dominant tensile non-double component, characteristic of volcanic explosions. Furthermore, we also found evidence for reverse polarity mechanisms in agreement with subsidence of a caldera, possibly indicating incremental activity of a ring fault. We discuss the possible contribution of a caldera to the evolving eruption dynamics and the need to improve geophysical monitoring of this island arc in general and acquire high-resolution submarine data Hunga Tonga Hunga Ha'apai in specific.

How to cite: Walter, T. R. and Cesca, S. and the GFZ-DLR-Geomar Task Force Team: Caldera subsidence during the Hunga-Tonga explosive eruption?, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13590, https://doi.org/10.5194/egusphere-egu22-13590, 2022.

Explosive volcanism periodically induces disturbances of the upper troposphere and low stratosphere. These injections of massive amount of aerosols, ash and gases perturb locally the physico-chemical balance of the impacted atmospheric layers, in particular the ozone concentration via heterogeneous chemistry on particles. On a larger scale some exceptional eruption can have a significant influence on the Earth radiative budget as it was the case following eruptions of El Chichon in 1982 and Mount Pinatubo in 1991.

On January 15, 2022, the Hunga-Tonga volcano erupted in the Tonga archipelago (20.5°S, 175.4°W). The Plinian eruption was of a rare intensity, especially because of the depth of the underwater caldera. The first estimates indicate a power between 10 and 15 Mt TNT, probably the most powerful since the eruption of Krakatoa in 1883. This short (~ 8min) but intense explosion whose pressure wave was observed all around the globe injected about 400 kt of material into the atmosphere (to be compared to the 20 Mt injected during the Mount Pinatubo eruption). The Volcano Stratospheric Plume (VSP) quickly moved westwards and then overflew the island of La Réunion (21°S, 55°E), located at ~12000 km away from Tonga.

In order to monitor the evolution of the VSP, lidar observations were performed at the Observatoire de Physique de l’Atmosphère de La Réunion (OPAR). This observatory is equipped with three lidars capable of stratospheric aerosols measurements at two wavelengths (355 nm and 532 nm). First observations were performed every night from 19 to 27 January 2022 when the first passage of the VSP occurred. The plume structures appeared to be highly variable along time, with altitudes ranging from 19 km to 36 km above the mean sea level while plume thicknesses were ranging from ~1 km to more than 3 km. Remarkable aerosol optical depth were associated with these stratospheric aerosol layers, up to 0.8 at 532 nm on January 21.

The temporal evolution of the VSP structure and optical properties will be presented and discussed.

How to cite: Baron, A., Payen, G., Duflot, V., Chazette, P., Khaykin, S., Hello, Y., Marquestaut, N., Ranaivombola, M., Bègue, N., Portafaix, T., and Cammas, J.-P.: Early evolution of the Hunga – Tonga Volcanic Plume from Lidar Observations at Reunion Island (Indian Ocean, 21°S, 55°E), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13599, https://doi.org/10.5194/egusphere-egu22-13599, 2022.

The 15 January 2022 eruption of the submarine Hunga Tonga-Hunga Ha'apai (HTHH) volcano (Tonga) ranks among the largest volcanic explosions of the satellite remote sensing era, and perhaps the last century. It shares many characteristics with the 1883 Krakatau eruption (Indonesia), including atmospheric pressure waves and tsunamis, and the phreatomagmatic interaction of magma and seawater likely played a major role in the dynamics of both events. A portion of the HTHH eruption column rose to lower mesospheric altitudes (~55 km) and the umbrella cloud extent (~500 km diameter at ~30-35 km altitude) rivalled that of the 1991 Pinatubo eruption, indicative of very high mass eruption rates. However, sulfur dioxide (SO₂) emissions measured in the HTHH volcanic cloud (~0.4 Tg) were significantly lower than the post-Pinatubo SO₂ loading (~10–15 Tg SO₂), and on this basis we would expect minimal climate impacts from the HTHH event. Yet, in the aftermath of the eruption satellite observations show a persistent stratospheric aerosol layer with the characteristics of sulfate aerosol, along with a large stratospheric water vapor anomaly. At the time of writing, the origin, composition and eventual impacts of this stratospheric gas and aerosol veil are unclear. We present the preliminary results of a multi-disciplinary approach to understanding the HTHH eruption, including 1D- and 3D-modeling of the eruption column coupled to a 3D atmospheric general circulation model (NASA’s GEOS-5 model), volatile mass balance considerations involving potential magmatic, seawater and atmospheric volatile and aerosol sources, and an extensive suite of satellite observations. Analysis of the HTHH eruption will provide new insight into the dynamics and atmospheric impacts of large, shallow submarine eruptions. Such eruptions have likely occurred throughout Earth’s history but have never been observed with modern instrumentation.

How to cite: Carn, S., Andrews, B., Aquila, V., Cauley, C., Colarco, P., Dufek, J., Fischer, T., Kenis, L., Krotkov, N., Li, C., Mastin, L., Newman, P., and Wallace, P.: Satellite observations and modeling of the 2022 Hunga Tonga-Hunga Ha'apai eruption, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13583, https://doi.org/10.5194/egusphere-egu22-13583, 2022.

In the frame of the Strateole 2 balloon project, 17 long-duration stratospheric balloons were launched from Seychelles in fall 2021. At the time of the main eruption of Hunga-Tonga on January 15 2022, two balloons were still in flight over the tropical Pacific, respectively at altitudes of 20 and 18.5 km, and distances of 2,200 and 7,600 km from the volcano. The balloon measurements include wind, temperature and pressure at a sampling rate of 1 Hz. Those observations of this extreme event at that altitude are unique.

In this presentation, we will describe the observations of multiple wave trains by the balloons. The signature of the Lamb wave and infrasounds are particularly striking. The characteristics of the eruption and its scenario will be examined using a synergy of stratospheric in situ observations, ground observations and geostationary satellite images. Finally, we will discuss the complementarity of balloon observations with respect to the ground network due to their altitude and geographic location with respect to the source.

How to cite: Podglajen, A., Garcia, R., Gerier, S., Hauchecorne, A., Hertzog, A., Le Pichon, A., Lott, F., and Millet, C.: Stratospheric observations of acoustic-gravity waves from the Hunga-Tonga eruption, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13593, https://doi.org/10.5194/egusphere-egu22-13593, 2022.

The Hunga Tonga eruption has generated an atmospheric plume rising above 40 km,  establishing an observational record. Due to the explosive nature of the eruption with a lot of water, the plume carried an unprecedented amount of water and a cloud of sulfated aerosols and possibly ultra-thin ashes was released. The aerosols have already persisted for four weeks with peak scatterring ratio initially above 200 that are still above 30 on many patches, as seen from CALIOP. These high values combined with low depolarization suggest a large amount of small sub-micronic spherical particles, confirmed by in situ balloon measurements. This is compatible with dominance of sulfated aerosols.

As the stratospheric flow has been mostly zonal with no breaking wave during the period and region of interest, and the horizontal shear dominates, the plume has been mostly dispersed in longitude keeping a similar latitudinal vertical pattern from the early days. A part has migrated to the tropical band reaching 10°N. Several concentrated patches have been preserved in particular a "mushroom" like pattern at 20S which has already circulated once around the Earth. . We will discuss the stability of this pattern in relation with vortical and thermal structures that are detected from several instruments and the meteorological analysis.

We will also discuss the likely impact on the stratospheric composition and the radiative effect on the yearly basis.  

How to cite: Legras, B., Khaykin, S., Podglajen, A., and Sellitto, P. and the ASTuS: Persistence Hunga Tonga plume in the stratosphere and its journey around the Earth., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13595, https://doi.org/10.5194/egusphere-egu22-13595, 2022.

The Hunga Tonga volcanic eruption on Jan. 15, 2022 released a highly energetic atmospheric pressure wave that was observed all around the globe in different types of measurements (e.g., barometers and infrasound sensors, satellites images, ionospheric measurements, etc.). In addition, the eruption triggered a meteo-tsunami followed by a series of tsunami waves. Tide gauges across the Pacific Ocean, the Atlantic and the Indian oceans recorded significant sea-level changes related to the primary eruption.

We focus our presentation on the imprint of tsunami waves on the ionosphere. We make use of an extensive collection of Global Navigation Satellites Systems (GNSS) data recorded by multi-constellation GNSS receivers across the Pacific Ocean and beyond. The observation of tsunami-induced ionospheric signatures is made possible by the efficient coupling of tsunami waves with the surrounding atmosphere and the generation of internal gravity waves (IGWs). With the help of GNSS systems (Beidou, GPS, Galileo, GLONASS, QZSS), ionospheric disturbances can be monitored and observed by utilizing the Total Electron Content (TEC) derived from the delay that the ionosphere imposes in the electromagnetic signals transmitted by the GNSS satellites. We identify and characterize the ionospheric TEC signatures following the passage of the Tonga tsunami. We investigate the influence of known key ambient parameters such as the local geomagnetic field, the tsunami propagation direction, and the distance to the tsunami source on the amplitude of the observed signatures. Moreover, we correlate the detected tsunami-induced TEC signatures with sea level measurements to assess their tsunami origins. And we contrast the identified TEC signatures in the Pacific Ocean with their analogs induced by the tsunami triggered by the Mar. 4, 2021 8.1 Mw Kermadec Islands earthquake. Both events took place relatively in the same geographical region, with the former being less complex (no meteo-tsunami, shorter duration, and about one order of magnitude smaller in amplitude). Finally, we provide estimations of the tsunami amplitude at the ocean level in the areas crossed by GNSS radio signals, some of them not covered by open ocean sea-level sensors (DART buoys).

How to cite: Munaibari, E., Rolland, L., Sladen, A., and Delouis, B.: Global ionospheric signature of the tsunami triggered by the 2022 Hunga Tonga volcanic eruption, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13578, https://doi.org/10.5194/egusphere-egu22-13578, 2022.

The population and built infrastructure of the Kingdom of Tonga are highly exposed to ocean- and climate-related coastal hazards. The archipelago was impacted on January 15, 2022, by a destructive tsunami caused by the Hunga Tonga-Hunga Ha'apai submarine volcanic eruption. Weeks later, several islands were still cut off from the world, this situation was made worse by covid-19-related international lockdowns and no precise idea of the magnitude and pattern of destruction. Like in most Pacific islands, the Kingdom of Tonga lacks an accurate population and infrastructure database. The occurrence of events such as this in remote island communities highlights the need for (1) precisely knowing the distribution of residential and public buildings, (2) evaluating what proportion of those would be vulnerable to a tsunami depending on various run-up scenarios, (3) providing tools to the local authorities for elaborating efficient evacuation plans and securing essential services outside the hazard zones. Using a GIS-based dasymetric mapping method previously tested in New Caledonia for assessing, calibrating, and mapping population distribution at high resolution, we produce maps that combine population clusters, critical elevation contours, and the precise location of essential services (hospitals, airports, shopping centers, etc.), backed up by before–after imagery accessible online. Results show that 62% of the population on the main island of Tonga lives in well-defined clusters between sea level and the 15 m elevation contour, which is also the value of the maximum tsunami run-up reported on this occasion. The patterns of vulnerability thus obtained for each island in the archipelago, are further compared to the destruction patterns recorded after the earthquake-related 2009 tsunami in Tonga, thereby also allowing us to rank exposure and potential for cumulative damage as a function of tsunami cause and source-area. By relying on low-cost tools and incomplete datasets for rapid implementation in the context of natural disasters, this approach can assist in (1) guiding emergency rescue targets, and (2) elaborating future land-use planning priorities for disaster risk-reduction purposes. By involving an interactive mapping tool to be shared with the resident population, the approach aims to enhance disaster-preparedness and resilience. It works for all types of natural hazards and is easily transferable to other insular settings.

How to cite: Thomas, B. E. O., Roger, J., and Gunnell, Y.: A rapid, low-cost, high-resolution, map-based assessment of the January 15, 2022 tsunami impact on population and buildings in the Kingdom of Tonga, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13580, https://doi.org/10.5194/egusphere-egu22-13580, 2022.

The eruption of Hunga volcano, Tonga is the most energetic event recorded by the infrasound component of the global International Monitoring System (IMS). Infrasound, acoustic-gravity and Lamb waves were recorded by all 53 operational stations after circling four times the globe. The atmospheric waves recorded globally exhibit amplitude and period comparable to the ones observed following the 1883 Krakatoa eruptions. In the context of the future verification of the Comprehensive Nuclear-Test-Ban Treaty, this event provides a prominent milestone for studying in detail infrasound propagation around the globe for almost one week as well as for calibrating the performance of the IMS network in a broad frequency band.

How to cite: Vergoz, J., Le Pichon, A., Listowski, C., Hupe, P., Pilger, C., Gaebler, P., Ceranna, L., Garcés, M., Marchetti, E., Labazuy, P., Mialle, P., Brissaud, Q., Näsholm, P., Shapiro, N., and Poli, P.: A global analysis of deep infrasound produced by the January 2022 eruption of Hunga volcano, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13598, https://doi.org/10.5194/egusphere-egu22-13598, 2022.

Low-frequency seismic energy whose spectrum is centered at certain narrow bands has been detected after violent volcano eruptions. Normal-mode analysis related this signal to the resonances between the atmosphere and the solid earth.
After the powerful eruption of Hunga Tonga-Hunga Ha’apai volcano on Jan. 15, 2022, this low-frequency signal is found on long period and very long period seismometers worldwide. The amplitude spectrum of the signal for this eruption consists of three clear peaks locating at 3.72, 4.61 and 6.07 mHz, instead of two distinct bands for previous cases. The spectrogram analysis shows that this low-frequency energy lasts for several hour and is independent of air wave arrival, while the cross-correlation result confirms that the signal travels as Rayleigh waves with a speed of 3.68 km/s. In this study, we summarize our findings on the observation, and show our synthetic waveforms to provide a possible explanation for the source of this signal. We suggest that the atmospheric oscillations near the volcano excited by the eruption act as an enduring external force on the surface of the solid earth, and produce Rayleigh waves propagating all over the world.

How to cite: Zhang, S., Wang, R., and Dahm, T.: Modeling low-frequency Rayleigh waves excited by the Jan. 15, 2022 eruption of Hunga Tonga-Hunga Ha’apai volcano, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13579, https://doi.org/10.5194/egusphere-egu22-13579, 2022.

The explosive eruption of the Hunga Tonga-Hunga Ha'apai volcano on January 15, 2022 triggered tsunami waves that were observed throughout the Pacific Ocean. In particular, the waves were recorded by several dozen deep-ocean DART stations located at source distances from hundreds to more than 10 thousand kilometers. Our study is aimed at analyzing tsunami waveforms recorded by DART stations in order to identify the formation mechanisms of this volcanogenic tsunami. Waveforms are processed using wavelet analysis. The arrival times of signals of different genesis are estimated making use robust physical assumptions, numerical modeling and satellite images. It has been found that in all records the tsunami signal is clearly observed long before the calculated moment of arrival of gravity surface waves caused by sources localized in the immediate vicinity of the volcano. On the records obtained by distant stations (~10000 km) dispersive gravity waves arrive with a delay of several hours after the signals following the passage of acoustic wave in the atmosphere. In addition to the analysis of waveforms, theoretical estimates of the amplitude of gravity waves in the ocean, caused by an acoustic wave in the atmosphere, will be presented. We also provide a theoretical estimate on how acoustic waves in the atmosphere manifest in pressure variations recorded by an ocean-bottom sensor.

This study was funded by a grant of the Russian Science Foundation № 22-27-00415, https://rscf.ru/en/project/22-27-00415/.

How to cite: Nosov, M., Sementsov, K., Kolesov, S., and Pryadun, V.: Volcanogenic tsunami on January 15, 2022: insights from deep-ocean measurements, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13591, https://doi.org/10.5194/egusphere-egu22-13591, 2022.

The Hunga Tonga-Hunga Ha’apai eruption of January 15 2022 was the culminating event of a sequence of seismic and volcanic events starting back in December 2021. The January 15 eruption manifested itself above the sea level with a number of phenomena, including the generation of a convective column ascending well into the stratosphere, pyroclastic flows travelling over the sea surface, an atmospheric pressure wave recorded by several instruments around the globe, and a tsunami, that represents the main focus of this study.

The tsunami that followed the eruption was observed both in the near-field and in the far-field, propagating across the entire Pacific Ocean and causing damage and loss of lives as far as Peru. In the near-field (Tonga archipelago) it is trickier to distinguish the damage induced by the impact of the eruption and the tsunami waves.

It is still not clear what the main generating mechanism for the ensuing tsunami was. In this contribution, several different hypotheses are investigated, adopting simplified models ranging from the submerged volcanic edifice collapse to the phreatomagmatic explosion and to the atmospheric pressure wave that was recorded across the entire globe. The propagation of the tsunami is simulated numerically with both non-dispersive and dispersive codes. Different spatial scales and resolutions are adopted to check the relative weight of the different generating mechanisms in the near- and in the far-field. Tentative conclusions are drawn by comparing the simulated results with the available experimental data in terms of tide-gauge records and near-field coastal impact.

How to cite: Armigliato, A., Angeli, C., Gallotti, G., Tinti, S., Zanetti, M., and Zaniboni, F.: Numerical investigations on different possible generating mechanisms for the tsunami following the January 15 2022 Hunga Tonga-Hunga Ha’apai eruption, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13589, https://doi.org/10.5194/egusphere-egu22-13589, 2022.

Meteotsunamis are long ocean waves generated by atmospheric disturbances. The Tonga volcano eruption on 15 January 2022 generated a Lamb pressure wave propagating all over the globe and generating a tsunami observed at most tide gauges in the world. A first atmospheric wave arrived 20 hours after the eruption on the French Mediterranean coasts and propagated southward. This abrupt atmospheric pressure change was recorded by hundreds of barometers of weather stations around Europe. A second one originating from Africa was observed four hours later with an attenuated amplitude. The first wave can be roughly defined by a sinusoid signal with a period close to one hour and an amplitude of 150 Pa. The associated tsunami was observed by the French stations of the HTM-NET network (https://htmnet.mio.osupytheas.fr/) [1]. Amplitudes range from a few cm to 15 cm and periods range from 20 min to 1 hour.

Numerical simulation of the tsunami is performed by the operational code Taitoko developed at CEA [2]. The nested multigrid approach is used to simulate the water waves propagating in the bay of Toulon. The meteotsunami is generated by calculating analytically the atmospheric pressure gradient in the momentum equation. Comparisons of time series between numerical solutions and records are very satisfactory in regions defined by a high resolution topo-bathymetry. A second tsunami simulation is performed by introducing a second pressure wave propagating in the North direction and reaching the HTM-NET stations 4 hours after the first arrival. This second pressure wave results in additional and higher tsunami water waves in agreement with records.

[1] Rey, V., Dufresne, C., Fuda, J. L., Mallarino, D., Missamou, T., Paugam, C., Rougier, G., Taupier-Letage, I., On the use of long term observation of water level and temperature along the shore for a better understanding of the dynamics: Example of Toulon area, France Ocean Dyn., 2020, https://doi.org/10.1007/s10236-020-01363-7.

[2] Heinrich, P, Jamelot, A., Cauquis, A., Gailler A., 2021. Taitoko, an advanced code for tsunami propagation, developed at the French Tsunami Warning Centers. European Journal of Mechanics - B/Fluids 88(84) . DOI: 10.1016/j.euromechflu.2021.03.001.

How to cite: Gailler, A., Heinrich, P., Rey, V., Hébert, H., Dupont, A., Listowski, C., Forestier, E., and Ntafis, S.: Observation and simulation of the meteotsunami generated in the Mediterranean Sea by the Tonga eruption on 15 January 2022, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13594, https://doi.org/10.5194/egusphere-egu22-13594, 2022.