Publications scientifiques

Southeast Asian deltas are highly threatened areas for flooding as a response to the combined effects of natural compaction and subsidence exacerbated by human impacts, e.g. oil, gas and water extraction, retention of sediment discharge due to river damming and sand mining, land use changes, sea-level rise and storm-induced water-level setup. Tide-induced water-level fluctuations on different time- and spatial scales, seasonal variations of freshwater runoff and sea-level setup can amplify the impact of sea-level rise and of storm surges on the coastal environment and its inhabitants.

Despite 20 years of control on eutrophication, episodes of summer hypoxia still occur in the Loire estuary, impacting water quality and posing a key scientific and management challenge. This work aimed to quantify the contribution of the benthic compartment to hypoxia in the Loire estuary by direct measurement of water–sediment fluxes and an in-depth understanding of the seasonal variations of oxides and phosphorus stocks.

In addition to traditional tide gauges, the ground-based global navigation satellite system reflectometry (GNSS-R) that utilizes signal-to-noise ratio data from a single GNSS receiver has become another promising alternative for sea level monitoring. However, its application is limited by retrieval precision, especially in large tidal variation environments. On the other hand, previous studies have focused on performance improvement by using post-processing strategies, which cannot support practical (near-) real-time applications.

Sea level changes are a complex and quite discussed topic in the media, mostly because of their relationship with “climate change”. The first instruments to evaluate sea level changes are the Tide Gauges (TG) that began to register data in 1700, at Amsterdam. The TG registrations are validated and homogenized, to be comparable, by PSMSL (Permanent Service for Mean Sea Level). The longest record is the one in Brest (France) that begins in 1807. They register the Relative Sea Level (RSL). In fact, the data show that the vertical movements on the continent strongly affect the RSL curves.

Coastal water level measurements represent one of the earliest geophysical measurements and allow an assessment of historical sea level rise and trends in tides, river flow and storm surge. However, recovery and digitization of archival tidal records have been much less widespread and systematic than, for example meteorological records. In this contribution, we discuss data rescue efforts and lessons learned in France, the United States and the United Kingdom, countries with early and extensive tide gauge networks by the mid-19th century.

Bayesian networks are probabilistic graphical models that are increasingly used to translate hydraulic boundary conditions during storm events into onshore hazards. However, comprehensive databases that are representative of the extreme and episodic nature of storms are needed to train the Bayesian networks. Such databases do not exist for many sites and many Bayesian networks are trained on data generated by process-based models. To our knowledge, they have not been trained exclusively on observational data for storm impact modeling.

This article presents a curated database of the sea-level measurements acquired by the network of the five geodetic tide gauges managed over French Polynesia by the Geodesy Observatory of Tahiti from 13 June 2009 to 28 January 2021.

Seasonal variability of the M₂ ocean tide can be detected at many ports, perhaps most. Examination of the cluster of tidal constituents residing within the M₂ tidal group can shed light on the physical mechanisms underlying seasonality. In the broadest terms these are astronomical, frictional–advective interactions, and climate processes; some induce annual modulations and some semiannual, in amplitude, phase, or both. This note reviews how this occurs and gives an example from each broad category.

Multi-satellite and Multi-Signal-to-Noise Ratio (SNR) types provide more basic data for the monitoring of sea level height by Global Navigation Satellite System Interferometric Reflectometry (GNSS-IR) technology. Few studies predict sea level height with high temporal resolution. This study proposes a theory based on GNSS-IR technology and Auto Regressive Integrated Moving Average (ARIMA) model. Taking the MAYG station as an example, the process of sea level height prediction and the determination of the best prediction scheme are shown.