Abstract
Modeling studies addressing daily to interannual coastal evolution typically relate shoreline change with waves, currents and sediment transport through complex processes and feedbacks. For wave-dominated environments, the main driver (waves) is controlled by the regional atmospheric circulation. Here a simple weather regime-driven shoreline model is developed for a 15-year shoreline dataset (2000–2014) collected at Truc Vert beach, Bay of Biscay, SW France. In all, 16 weather regimes (four per season) are considered. The centroids and occurrences are computed using the ERA-40 and ERA-Interim reanalyses, applying k-means and EOF methods to the anomalies of the 500-hPa geopotential height over the North Atlantic Basin. The weather regime-driven shoreline model explains 70% of the observed interannual shoreline variability. The application of a proven wave-driven equilibrium shoreline model to the same period shows that both models have similar skills at the interannual scale. Relation between the weather regimes and the wave climate in the Bay of Biscay is investigated and the primary weather regimes impacting shoreline change are identified. For instance, the winter zonal regime characterized by a strengthening of the pressure gradient between the Iceland low and the Azores high is associated with high-energy wave conditions and is found to drive an increase in the shoreline erosion rate. The study demonstrates the predictability of interannual shoreline change from a limited number of weather regimes, which opens new perspectives for shoreline change modeling and encourages long-term shoreline monitoring programs.
Highlights
Sandy coasts are complex environments that are under increasing threat posed by anthropogenic pressures and climate change
A preliminary analysis indicates that changing the three weather regimes causes no change to the model output. Both the measured and simulated shoreline time series are detrended with a linear fit to remove the long-term trend, as this study aims at investigating the interannual variability of shoreline change
The seasonal wave characteristics off the SW French Atlantic coast appear to be strongly related with the weather regimes
Summary
Sandy coasts are complex environments that are under increasing threat posed by anthropogenic pressures and climate change. Shoreline evolution on timescales from hours (cf storms) to years has recently been simulated with fair skill using wave-driven empirical equilibrium-based models (e.g., Davidson and Turner 2009; Yates et al 2009; Davidson et al 2013; Castelle et al 2014; Splinter et al 2014a). These models can reproduce the interannual shoreline variability that sometimes exceeds the seasonal variability (e.g., Castelle et al 2014). Directly using atmospheric conditions as inputs in shoreline models appears
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