Publications scientifiques

In the coastal ocean zones, satellite altimetry data processing and interpretation poses specific difficulties, due to the interaction of the radar signal with land topography, inaccuracies in some of the geophysical corrections and to the fast changes in the sea level. In order to optimize the completeness and the accuracy of the sea surface height information derived from satellite altimetry in coastal ocean areas, a dedicated post-processing software, called X-TRACK, has been developed by the Center of Topography of the Ocean and Hydrosphere in Toulouse.

Radar water level sensors provide several advantages over the older water level instruments. They require less effort to install than float-well, bubbler, or pressure sensor systems. Radar sensors require less maintenance than traditional water-level sensors because they are not in contact with the water. Because radar is a “non-contact” measurement method, it is not susceptible to being obstructed by sediment or debris and does not require that sediment be flushed from a stilling well. Radar water-level sensors may not work at all sites.

For at least 20 years, nadir altimetry satellite missions have been successfully used to first monitor the surface elevation of oceans and, shortly after, of large rivers and lakes. For the last 5–10 years, few studies have demonstrated the possibility to also observe smaller water bodies than previously thought feasible (river smaller than 500 m wide and lake below 10 km²). The present study aims at quantifying the nadir altimetry performance over a medium river (200 m or lower wide) with a pluvio-nival regime in a temperate climate (the Garonne River, France).

Le projet relatif à la reconstruction et au contrôle de la série analogique des hauteurs d’eau observées à Saint-Nazaire, financé par le MEEM, la région Pays de Loire et par le Shom, a débuté le 19 août 2013. Cette étude s’inscrit dans le cadre du programme international GLOSS (Global Sea Level Observing System) de la Commission océanographique intergouvernementale (COI) de l’UNESCO et du SOERE – SO SONEL.

Le Passage du Gois est une chaussée submergée à chaque marée. Il permet de relier le continent à l’île de Noirmoutier à marée basse en traversant la Baie de Bourgneuf. L’érosion constatée le long de la chaussée côté Sud remet en cause sa pérennité. Une analyse des processus hydro-sédimentaires à l’origine de cette érosion a été réalisée pour la DREAL Pays-de-la-Loire dans le cadre d’un projet de classement du site. Le Gois est à l’origine une édification sédimentaire issue d’un hydrodynamisme particulier dans la baie.

The question of the impacts of climate change and sea level rise on small islands is currently much discussed. The many thousands of Pacific islands in their different contexts (geodynamic, climatic, etc.) and the insufficient data available explain why it is difficult to clearly discern the specific role of climate change in the recent evolution of these islands. To address this question, we investigated the recent changes affecting 21 islets in New Caledonia's lagoon.

Filamentous sulfur bacteria of the genus Beggiatoa form large mats covering the sediment in the shallow waters of a Guadeloupean mangrove (French West Indies). The abundance of these bacteria varies over the year and their trophic role may, therefore, also vary. We investigated this variation by conducting a survey examining the stable isotopic compositions of four grazers and four food sources during nine sampling sessions in three different periods of the year.