Letter abstract
Nature Geoscience 1, 169 - 172 (2008)
Published online: 17 February 2008 | doi:10.1038/ngeo127
Subject Categories: Geomorphology | Oceanography
Significant contribution of the 18.6 year tidal cycle to regional coastal changes
N. Gratiot1,6, E. J. Anthony2, A. Gardel2, C. Gaucherel3, C. Proisy4 & J. T. Wells5
Although rising global sea levels will affect the shape of coastlines over the coming decades1, 2, the most severe and catastrophic shoreline changes occur as a consequence of local and regional-scale processes. Changes in sediment supply3 and deltaic subsidence4, 5, both natural or anthropogenic, and the occurrences of tropical cyclones4, 5 and tsunamis6 have been shown to be the leading controls on coastal erosion. Here, we use satellite images of South American mangrove-colonized mud banks collected over the past twenty years to reconstruct changes in the extent of the shoreline between the Amazon and Orinoco rivers. The observed timing of the redistribution of sediment and migration of the mud banks along the 1,500 km muddy coast suggests the dominant control of ocean forcing by the 18.6 year nodal tidal cycle7. Other factors affecting sea level such as global warming or El Niño and La Niña events show only secondary influences on the recorded changes. In the coming decade, the 18.6 year cycle will result in an increase of mean high water levels of 6 cm along the coast of French Guiana, which will lead to a 90 m shoreline retreat.
- Laboratoire d'Ecologie Littorale, IRD Guyane, BP165, route de Montabo, Cayenne, 97323, French Guiana
- Université du Littoral Côte d'Opale, Laboratoire d'Océanologie et de Géosciences, CNRS, UMR 8187 LOG, 32, Avenue Foch, 62930 Wimereux, France
- INRA, UMR AMAP, Boulevard de la Lironde, TA A51/PS2, 34398 Montpellier cedex 5, France
- IRD, UMR AMAP, Boulevard de la Lironde, TA A51/PS2, 34398 Montpellier cedex 5, France
- Virginia Institute of Marine Science, College of William and Mary, Box 1346, Gloucester Pt., Virginia 23062, USA
- Present address: LTHE (UMR IRD-CNRS-UJF-INPG) 1025, rue de la piscine, BP 53, 38041 Grenoble, France
Correspondence to: N. Gratiot1,6 e-mail: nicolas.gratiot@ird.fr
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