Likely and High-End Impacts of Regional Sea-Level Rise on the Shoreline Change of European Sandy Coasts Under a High Greenhouse Gas Emissions Scenario

Rémi Thiéblemont,Alexandra Toimil,Iñigo J Losada,Gonéri Le Cozannet,Benoit Meyssignac

doi:10.3390/w11122607

Rémi Thiéblemont, Alexandra Toimil + Show 3 more

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https://doi.org/10.3390/w11122607

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Abstract

Sea-level rise (SLR) is a major concern for coastal hazards such as flooding and erosion in the decades to come. Lately, the value of high-end sea-level scenarios (HESs) to inform stakeholders with low-uncertainty tolerance has been increasingly recognized. Here, we provide high-end projections of SLR-induced sandy shoreline retreats for Europe by the end of the 21st century based on the conservative Bruun rule. Our HESs rely on the upper bound of the RCP8.5 scenario “likely-range” and on high-end estimates of the different components of sea-level projections provided in recent literature. For both HESs, SLR is projected to be higher than 1 m by 2100 for most European coasts. For the strongest HES, the maximum coastal sea-level change of 1.9 m is projected in the North Sea and Mediterranean areas. This translates into a median pan-European coastline retreat of 140 m for the moderate HES and into more than 200 m for the strongest HES. The magnitude and regional distribution of SLR-induced shoreline change projections, however, utterly depend on the local nearshore slope characteristics and the regional distribution of sea-level changes. For some countries, especially in Northern Europe, the impacts of high-end sea-level scenarios are disproportionally high compared to those of likely scenarios.

Highlights

The rising of the global mean sea-level (GMSL) is observed since the early 20th century and is projected to continue and further accelerate over the 21st century [1,2], posing a major challenge for coastal regions worldwide [3]
Since we focus on the impacts of sea-level rise only, shoreline changes caused by processes unrelated to sea-level rise are not included in our projections and should be considered for local assessment
In sectors such as the Mediterranean and North Seas, sea-level rise projections exceed 0.8 m. These projections emphasize a substantial contrast of sea-level change projections at the European scale, which is dominated by a gradual northward decrease in the magnitude of sea-level rise

Summary

Introduction

The rising of the global mean sea-level (GMSL) is observed since the early 20th century and is projected to continue and further accelerate over the 21st century [1,2], posing a major challenge for coastal regions worldwide [3]. Since the 1970s, the ocean thermal expansion and melting of land glaciers, largely caused by the anthropogenic global warming [4], are the main contributors to the GMSL rise. While the thermal expansion is expected to continue increasing over the 21st century, the total contribution of ice mass loss by ice-sheets is projected to become more substantial, and it is the first driver of the GMSL rise acceleration since 1993 [5,6,7]. Water mass transfer from land to the ocean—due, e.g., to mountain glaciers and ice-sheets melting or groundwater extraction—induces regional changes by altering the

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