Abstract
Extreme sea levels, caused by storm surges and high tides, can have devastating societal impacts. To effectively protect our coasts, global information on coastal flooding is needed. Here we present the first global reanalysis of storm surges and extreme sea levels (GTSR data set) based on hydrodynamic modelling. GTSR covers the entire world's coastline and consists of time series of tides and surges, and estimates of extreme sea levels. Validation shows that there is good agreement between modelled and observed sea levels, and that the performance of GTSR is similar to that of many regional hydrodynamic models. Due to the limited resolution of the meteorological forcing, extremes are slightly underestimated. This particularly affects tropical cyclones, which requires further research. We foresee applications in assessing flood risk and impacts of climate change. As a first application of GTSR, we estimate that 1.3% of the global population is exposed to a 1 in 100-year flood.
Highlights
Extreme sea levels, caused by storm surges and high tides, can have devastating societal impacts
The performance of the Global Tide and Surge Reanalysis (GTSR) time series is similar to the performance of other hydrodynamic models that cover a large geographic domain
The validation of GTSR shows that extreme sea levels are generally underestimated but that the differences with observed extreme sea levels are rather small
Summary
Extreme sea levels, caused by storm surges and high tides, can have devastating societal impacts. Some applications require time series of sea levels (instead of extreme values), such as: assessing interannual variability; assessing the impact of changes in storm regimes; and the modelling of past events. Such time series can be obtained from tide gauge observations, but many regions at risk have insufficient numbers of tide gauges and/or record lengths available to reliably estimate extreme sea levels. More advanced techniques based on altimetry data have been developed[20], but the limited length of altimetry records prevent their application to low-probability extreme events[21,22] Due to these data limitations, there is still limited understanding of the global coastal flood hazard, even under current (stationary) climate conditions. Tides are modelled separately using a recent update of the Finite Element Solution (FES2012)
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