Abstract
Compound flooding arises from storms causing concurrent extreme meteorological tides (that is the superposition of storm surge and waves) and precipitation. This flooding can severely affect densely populated low-lying coastal areas. Here, combining output from climate and ocean models, we analyse the concurrence probability of the meteorological conditions driving compound flooding. We show that, under a high emissions scenario, the concurrence probability would increase globally by more than 25% by 2100 compared to present. In latitudes above 40o north, compound flooding could become more than 2.5 times as frequent, in contrast to parts of the subtropics where it would weaken. Changes in extreme precipitation and meteorological tides account for most (77% and 20%, respectively) of the projected change in concurrence probability. The evolution of the dependence between precipitation and meteorological tide dominates the uncertainty in the projections. Our results indicate that not accounting for these effects in adaptation planning could leave coastal communities insufficiently protected against flooding.
Highlights
Compound flooding arises from storms causing concurrent extreme meteorological tides and precipitation
Time series of meteorological tides were obtained as the superposition of storm surges[1] and waves[1,32,33], which were available from ocean model simulations forced with reanalysis data for the observed past[34], and with global climate models (GCMs) climate projections of the Coupled Model Intercomparison Project Phase 5 (CMIP5) for estimates of climate change under a high anthropogenic greenhouse gas emissions scenario (RCP8.5)[35]
Given that higher-resolution input data could improve the representation of extreme events[1,25,36], especially for tropical cyclones (TCs)[25,37,38,39], we improved the representation of TCdriven meteorological tides in the reanalysis-based dataset
Summary
Compound flooding arises from storms causing concurrent extreme meteorological tides (that is the superposition of storm surge and waves) and precipitation. Present-day compound flood hazard has been assessed for the United States[8], Australia[21,22], and Europe[9,10,14,15,23] by considering co-occurring sea-level and either precipitation or river discharge extremes. Most of these studies used field observations of sea level, which do not cover the entire global coastline[10,24]. The above, in combination with the expected future increase in coastal population, highlights the need for a comprehensive assessment of the meteorological drivers of compound flooding and their response to climate change
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