Publications scientifiques

The storm surge is the non-tidal component of coastal sea-level. It responds to the atmosphere both through the direct effect of atmospheric pressure on the sea-surface, and through Ekman transport induced by wind-stress. Tide gauges have been used to measure the sea-level in coastal cities for centuries, with many records dating back to the 19th-century or even further, at times when direct pressure observations were scarce.

In this study, alternatively to the megathrust, we identify upper-plate normal faults orthogonal to the trench as a possible tsunami source along the Lesser Antilles subduction zone. The Morne Piton fault system is such a trench-perpendicular upper crustal fault at the latitude of Guadeloupe.

In the context of climate change, height and frequency variations in extreme sea levels (ESLs) are studied using deterministic and probabilistic approaches. However, this type of approach does not highlight the dynamic effects (waves, currents) generated by metocean events (storms, cyclones, long swells, and tsunamis) beyond their effects on sea levels. In particular, ESL estimates are calculated by considering the main determining physical factors but cannot include all the effects of these factors. Ultimately, this can lead to confusion between ESL and hazard.

Understanding and precisely dating the sedimentological imprint of storm-induced back-barrier washover deposits is challenging, even more so in macro-tidal environments. Indeed, in such a situation, significant storms may not lead to any washover deposits, for instance if they occurred during low tide. To tackle this challenge, we propose a method based on crossing sedimentology, historical impacts from archives and weather-marine data, together with dating, statistics and modeling technique.

In this study, we estimate the absolute vertical land motions at three tidal stations with collocated Global Navigation Satellite System (GNSS) receivers over French Polynesia during the period 2007–2020, and obtain, as ancillary results, estimates of the absolute changes in sea level at the same locations. To verify our processing approach to determining vertical motion, we first modeled vertical motion at the International GNSS Service (IGS) THTI station located in the capital island of Tahiti and compared our estimate with previous independent determinations, with a good agreement.

In this data paper, the sea level time series at Socoa (Saint-Jean-de-Luz, southwestern France) is extended through a data archaeology exercise. We conducted a comprehensive study of national and local archives to catalogue water level records stored in ledgers (handwritten record books) and charts (marigrams from mechanical float gauges), along with other associated documents (metadata). A dedicated effort was undertaken to preserve more than 2000 documents by archiving them in digital formats.

As sea levels are rising, the number of chronic flooding events at high tide is increasing across the world coastlines. Yet, many events reported so far either lack observational evidence of flooding, or relate to coastal areas where ground subsidence or oceanic processes often enhance climate change-induced sea-level rise (SLR). Here we present observational and modelling evidence of high-tide flooding events that are unlikely to occur without SLR in French Guiana, where sea-level rise rates are close to the global average and where there is no significant ground subsidence.

La mesure et l’étude de la variation du niveau de la mer en zone côtière sont un enjeu scientifique et sociétal majeur. Les mesures marégraphiques montrent des tendances de quelques millimètres par an et doivent être associées à des mesures géodésiques permettant de séparer le signal du niveau de la mer du mouvement vertical continental. Il a été montré que le couplage de mesures GNSS et de gravimétrie absolue améliore la compréhension des signaux marégraphiques.

Dans le contexte actuel de changement climatique, l’apport de séries temporelles du niveau de la mer, pluridécennales à séculaires, se révèle primordial pour mieux appréhender les risques côtiers futurs. En France, de nombreuses observations systématiques du niveau de la mer au moyen de marégraphes mécaniques ont été initiées dès le milieu du XIXe siècle. Pour exploiter ces données, il est d’abord nécessaire de numériser ce patrimoine scientifique et culturel et de valider les nouvelles données.