The Wadden Sea in transition - consequences of sea level rise

Abstract

The impact of sea level rise (SLR) on the future morphological development of the Wadden Sea (North Sea) is investigated by means of extensive process-resolving numerical simulations. A new sediment and morphodynamic module was implemented in the well-established 3D circulation model GETM. A number of different validations are presented, ranging from an idealized 1D channel over a semi-idealized 2D Wadden Sea basin to a fully coupled realistic 40-year hindcast without morphological amplification of the Sylt-Rømøbight, a semi-enclosed subsystem of the Wadden Sea. Based on the results of the hindcast, four distinct future scenarios covering the period 2010–2100 are simulated. While these scenarios differ in the strength of SLR and wind forcing, they also account for an expected increase of tidal range over the coming century. The results of the future projections indicate a transition from a tidal-flat-dominated system toward a lagoon-like system, in which large fractions of the Sylt-Rømøbight will remain permanently covered by water. This has potentially dramatic implications for the unique ecosystem of the Wadden Sea. Although the simulations also predict an increased accumulation of sediment in the back-barrier basin, this accumulation is far too weak to compensate for the rise in mean sea level.

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Notes

  1. 1.

    The sediment volume of the intertidal flats is defined here as the amount of sediment stored between mean low and mean high water, where all areas above mean high water are considered dry and not taken into account.

  2. 2.

    AufMod project Functional Seabed Model, Federal Maritime and Hydrographic Agency (BSH) (http://www.mdi-de.org)

  3. 3.

    https://doi.org/10.1594/WDCC/coastDat-2_TRIM-NP-2d data request to: elke.meyer@hzg.de

  4. 4.

    https://doi.org/10.1594/WDCC/coastDat-2_COSMO-CLM

  5. 5.

    Note that 60 μm sediment is treated as a fine non-cohesive sand.

  6. 6.

    Faculty of Civil Engineering and Geosciences, TU Delft, z.b.wang@tudelft.nl

  7. 7.

    Norddeutscher Verbund zur Förderung des Hoch- und Höchstleistungsrechnens

  8. 8.

    The measured bathymetry was generated in the same way as the initial bathymetry by merging fragmented measurements into a bathymetry that covers the entire area.

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Acknowledgements

We want to thank Mick van der Wegen and two anonymous reviewers for their thoughtful comments, which helped to substantially improve this manuscript. This study was conducted in the context of a trilateral cooperation among German, Dutch, and Danish coastal administrations on the future morphological development of the Wadden Sea under climate change. The authors want to thank the partners from Deltares (NL) and Kystdirektoratet (DK) for constructive discussions. The project SH-TREND was financed by the Schleswig-Holstein Ministry of Energy, Agriculture, the Environment and Rural Areas. We are grateful to Knut Klingbeil for the code development and maintenance of GETM. Supercomputing power was provided by the North-German Supercomputing Alliance (HLRN). The work of Elisabeth Schulz was supported by the project MOREWACC (Morphodynamic response of the Wadden Sea to climate change) funded by the German Research Foundation as BU 1199/21-1 under the umbrella of the Priority Programme SPP 1889 on Regional Sea Level Change and Society.

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Correspondence to Johannes Becherer.

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This article is part of the Topical Collection on the 18th conference on Physics of Estuaries and Coastal Seas (PECS), Scheveningen, Netherlands, 9–14 October 2016

Responsible Editor: Mick van der Wegen

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Becherer, J., Hofstede, J., Gräwe, U. et al. The Wadden Sea in transition - consequences of sea level rise. Ocean Dynamics 68, 131–151 (2018). https://doi.org/10.1007/s10236-017-1117-5

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Keywords

  • Sea level rise
  • Morphodynamic simulation
  • Wadden Sea