Coastal Environmental Changes: Impact of sea LEvel rise
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The CECILE project : sea level rise and coastal erosion
Improving our understanding of coastal impacts of sea level rise since 1950 and for the XXIst century
Ocean warming, mountain and polar glaciers melting are among the major consequences of climate change. Since the late XIXth century, these processes caused a rise of global sea level of 20cm. This rate of sea level rise is now reaching 3.2mm/yr and is expected to increase during the XXIst century. Far from being uniform, sea level rise displays regional variability, which can be amplified or mitigated by regional and local vertical ground motions.
Sea level rise is expected to increase shoreline erosion and the permanent submersion of low lying coastal areas. However, the actual impact of this process to present-days shoreline changes remains difficult to quantify. Through the CECILE project, we reconstructed sea level changes and analyzed their impacts for recent shorelines evolutions in several French outersee territories. This work has been completed by projections of future sea level changes (up to 2100). The project’s results are now available and usable for coastal risk prevention plans.
Looking for possible correlations between the spatial variability of sea level rise and shoreline changes
While sea level rose according to the global average in some regions, its rate was two to three times quicker than the global average since 1950 in some Pacific regions and it remained almost stable in others. Can we identify different regional patterns in shoreline changes depending on the regional variability in sea level changes? Within the CECILE project, we used observations and reconstructions of sea level changes to test whether coastal erosion is more likely when sea level is rising faster. The coastal sites of the project included european and french coasts (North Atlantic), but also outersees territories (Southern Pacific : New Caledonia and French Polynesia, Indian Ocean : La Réunion ; French Caribbean). The results indicate that in many cases, sea level rise impacts for shorelines are hidden behind other natural processes (storms, cyclones, waves, currents…) and anthropogenic actions (coastal defenses, indirect human actions…). However, during the XXIst century, as sea level rise will likely reach 0.5 to 1m, a shift in the behavior of coastal systems is expected, so that a major societal impact is expected in densely populated coastal regions.
From Becker et al. (2011) :linear trends of sea level changes in the Pacific over 1950-2009. This reconstruction has been obtained within the CECILE project using long tide gauge measurements and the modes of variability from the DRAKKAR ocean circulation model, forced with ERA-40 winds
Information about the project
The CECILE project is a public-private research project supported by the French National Agency for Research and coordinated by Anny Cazenave (LEGOS) and Gonéri Le Cozannet (BRGM). The partners of the project were:
- The Laboratoire d'Etudes en Géophysique et Océanographie Spatiales (LEGOS – UMR 5566) – (coordination scientifique)
- The BRGM (French Geological Survey) (coordination du projet)
- The Centre National de la Recherche Scientifique / Groupe d'Etude de l'Atmosphère Météorologique, (CNRM-GAME – URA-1357)
- The university of La Rochelle (Laboratoire LIttoral ENvironnement et SociétéS – UMR 6250)
- CREOCEAN (Coastal environmental and engineering company)
- The Service hydrographique et Océanographique de la Marine (SHOM)
- The Centre Européen de Recherche et de Formation en Calcul Scientifique (Cerfacs)
The project started in January 2010 and finished in December 2013. ANR funded 865 650€ while the total cost of the project is estimated at 2 529 455 €.