Extreme sea levels in the context of climate change

<p>The objective of this study is to investigate how extreme sea levels are changing, at a centennial time scale, in the context of climate change. We focus on Brest tide gauge (France), one of the longest time series in the world. First observations were recorded in 1701, and hourly data have been registered continuously since 1846 with little gaps. These data have been  carefully processed, in order to ensure good quality, especially regarding the datum continuity (Pouvreau, 2008) and stability (Poitevin, 2019).</p><p>Here, we investigate the evolution of the storm surges over the last 170 years. We focus on the skew surge, defined as the difference between the maximum observed water level and the maximum predicted tidal level (taking into account the mean sea level rise). This parameter is directly linked to the atmosphere variations, and may be correlated with regional climate parameters, such as the North Atlantic Oscillation (Menéndez and Woodworth, 2010). But it is also correlated with the evolution of the storminess in the North Atlantic. One of the challenges is to separate the natural interannual variability of the sea level from the long term trends at a centennial time scale.</p><p>We will discuss the variability of the storm surges, in terms of changes in the 99th percentile and the 5-year return period level. Statistical analysis will be based on extreme values theory (e.g. Generalized Extreme Value distribution, General Pareto Distribution). Correlation with other parameters such as the significant wave height (from buoys) and the wind and storm tracks (from global reanalysis, e.g. ERA5 from ECMWF) will also be investigated.</p><p>References<br>Menéndez M., Woodworth P. L. (2010). Changes in extreme high water levels based on a quasi-global tide-gauge dataset. J Geophys Res 115:C10011.<br>Poitevin (2019). Variabilité du niveau marin relatif le long du littoral de Brest (France) par combinaison de méthodes géodésiques spatiales (altimétrie radar, InSAR et GPS). PhD thesis, University of La Rochelle.<br>Pouvreau N. (2008). Trois cents ans de mesures marégraphiques en France : outils, méthodes et tendances des composantes du niveau de la mer au port de Brest. PhD thesis, University of La Rochelle.<br><br><br></p><p> </p>