Abstract

AbstractClimate change is very likely to cause a global acceleration in sea-level rise (SLR). The projected acceleration of SLR will also affect the Wadden Sea. In addition to an accelerated SLR, gas and salt extraction will cause subsidence that adds to an increase in water depth in the tidal basins. This will have consequences for the sediment budget of the Wadden Sea and especially for the intertidal flats that have a high ecological value. This synthesis presents projections of the future state of the Dutch Wadden Sea for the years 2030, 2050 and 2100.The projected changes in mean sea level by 2100 for Den Helder and Delfzijl are above the global mean projections, mainly due to the above-average ocean dynamics and glacio-isostatic adjustment contributions in the regional projections. The projected rise in mean sea level for 2100 with relation to 2018 in these locations is 0.41m, 0.52m and 0.76m for, respectively, the RCP2.6, RCP 4.5 and RCP8.5 climate scenarios.When we combine the presented SLR scenarios with the subsidence estimates and compare these rates to the critical rates for ‘drowning’ of intertidal flats that were calculated for the individual tidal basins, we can determine the moment that the maximum imported sediment volume can no longer compensate the increase in accommodation space in a basin and the intertidal flats will start to diminish in surface area and/or height. In the RCP2.6 scenario, the projected rates of relative SLR will be below the critical rate for drowning of the inlet systems in the Dutch Wadden Sea. For the RCP4.5 scenario, the critical SLR rate will be exceeded for Vlie Inlet in 2030, and for the RCP8.5 scenario the critical SLR rate will be exceeded for Vlie Inlet in 2030, Texel Inlet in 2050 and Ameland Inlet in 2100. For the other basins the critical rate will not be exceeded until 2100 or later.The way the intertidal flats in a basin will react to ‘drowning’ is not clear beforehand. It is highly possible that erosion of flats in one place will produce the sediment to maintain flats in other places. Tidal flats close to the sediment-delivering tidal inlet are not likely to disappear, because there the balance between supply and erosion is not likely to change.

Highlights

  • When we combine the presented sea-level rise (SLR) scenarios with the subsidence estimates and compare these rates to the critical rates for ‘drowning’ of intertidal flats that were calculated for the individual tidal basins, we can determine the moment that the maximum imported sediment volume can no longer compensate the increase in accommodation space in a basin and the intertidal flats will start to diminish in surface area and/or height

  • Climate change will very likely cause a global acceleration of sea-level rise (SLR)

  • In addition to an accelerated SLR, gas and salt extraction will cause subsidence that adds to an increase in water depth in the tidal basins in the Dutch part of the Wadden Sea

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Summary

Introduction

Climate change will very likely cause a global acceleration of sea-level rise (SLR). The projected acceleration of SLR will affect the Wadden Sea. This synthesis summarizes the information presented in the papers by Vermeersen et al (2018), Fokker et al (2018) and Wang et al (2018) in this special issue of the Netherlands Journal of Geosciences and combines projections of local sea level, subsidence and sediment transport into an assessment of the future state of the Dutch part of the Wadden Sea. We will restrict ourselves to projections of the future morphological development using the SLR scenarios presented by Vermeersen et al (2018) in combination with the prognoses for subsidence caused by gas and salt extraction for the individual fields in the Wadden Sea by Fokker et al (2018). This was superimposed on the projected rates for the Dutch part of the Wadden Sea

Data and methods
Natural causes of subsidence
Anthropogenic causes of subsidence
Measuring subsidence
Future subsidence in the Dutch Wadden Sea
Effect of an increase in sediment accommodation space
SLR scenario
What will the future Wadden Sea look like?
Full Text
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