Abstract
Sea-level rise represents a severe hazard for populations living within low-elevation coastal zones and is already largely affecting coastal communities worldwide. As sea level continues to rise following unabated greenhouse gas emissions, the exposure of coastal communities to inundation and erosion will increase exponentially. These impacts will be further magnified under extreme storm conditions. In this paper, we focus on one of the most valuable coastal real estate markets globally (Palm Beach, FL). We use XBeach, an open-source hydro and morphodynamic model, to assess the impact of a major tropical cyclone (Hurricane Matthew, 2016) under three different sea-level scenarios. The first scenario (modern sea level) serves as a baseline against which other model runs are evaluated. The other two runs use different 2100 sea-level projections, localized to the study site: (i) IPCC RCP 8.5 (0.83 m by 2100) and (ii) same as (i), but including enhanced Antarctic ice loss (1.62 m by 2100). Our results show that the effective doubling of future sea level under heightened Antarctic ice loss amplifies flow velocity and wave height, leading to a 46% increase in eroded beach volume and the overtopping of coastal protection structures. This further exacerbates the vulnerability of coastal properties on the island, leading to significant increases in parcel inundation.
Highlights
Human development is disproportionately concentrated around coastal trading hubs
We first use a model run under current sea level as a baseline for comparison, we investigate how coastal morphology, wave, current velocities, and land inundation would change under two sea-level scenarios: one representing a classic sea-level projection following a worst-case IPCC scenario (RCP8.5, Hausfather and Peters 2020), the other one including to the previous a significant Antarctic ice sheet collapse (DeConto and Pollard 2016)
This study focuses on how one of the most valuable coastal areas globally would be affected by a tropical cyclone under extreme future sea level scenarios
Summary
Between 94 million and 150 million people are currently living within areas at risk of inundation under future sea-level rise by the year 2100 (Kopp et al 2017). This number is expected to grow as lowlying coastal regions see continued population expansion. Representative Concentration Pathways (RCP) 2.6 and 8.5, respectively (Portner et al 2019). Within these predictions, debate persists as to the amount in which ice sheets will contribute to GMSL rise in the future. The physical processes still have significant uncertainties, and some studies have shown the possibility to fit geological constraints without ice-shelf and ice-cliff instability (Edwards et al 2019)
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