Morphodynamic response of the Wadden Sea to climate change (MOREWACC)

德国湾的瓦登海从荷兰的登海尔德延伸到丹麦的斯卡灵根，是受海平面上升威胁的沿海地区的原型。瓦登海面积的50%以上是潮间带，仅在潮汐周期的一部分被水淹没。这形成了瓦登海独特的沿海生态系统，该生态系统可以通过积累北海的沉积物而在上个世纪的海平面上升中生存下来，其速度使潮间带平面与海平面上升保持同步。 关键的问题是，海平面上升到什么速度，瓦登海的沉积物积累就足够了。这是一个复杂的问题，因为流入瓦登海的沉积物流量取决于海平面上升的速度本身，对气候变化的其他后果，以及对沉积物的可用性在一个高度非线性的方式。它是已知的净沉积通量是由潮汐不对称造成的非线性涨潮和水平密度差异，由于净降水和运行，以及瓦登海的冷却或加热。非线性涨潮的特征取决于海平面上升（更有活力的潮汐，潮差增加）和水平密度梯度可能会大大改变与气候有关的降水/蒸发和冷却/加热的变化。此外，沉积物通量对风的强度和方向很敏感，而风的强度和方向也容易受到气候变化的影响。 虽然关于沿海区沉积物动力学的知识使得能够对瓦登海的沉积物输运进行现实的模型模拟，但对形态动力学变化的预测仍然使用高度简化的垂直综合模型。因此，从这些模型中获得的知识非常有限，因此，本项目的主要目标是利用一个基于过程的模型，评估瓦登海在沉积物可利用性发生变化的条件下对海平面上升和气候变化其他方面可能作出的形态反应。由此，将包括瓦登海沉积物输运的主要驱动力。首先，这些模拟将进行系统的方式使用理想化的测深，确定在瓦登海的形态动力学变化的最关键的过程。利用这些水深测量，可以结合外部强迫的其他变化（降水蒸发、冷却加热、风浪强迫）评估海平面上升对沉积物积累的影响。在SPP的第二阶段，预计将进一步提高超级计算能力，这些模拟将在瓦登海的现实潮汐盆地进行。在这两个阶段中，盐沼的动态将明确包括在内。

The Wadden Sea of the German Bight stretching from Den Helder in The Netherlands to Skallingen in Denmark is a prototype for a coastal region under threat by sea level rise. Over 50% of the Wadden Sea area consists of intertidal flats which are submerged by water only during a part of the tidal cycle. This shapes the unique coastal ecosystem of the Wadden Sea which could survive the sea level rise of the last centuries by accumulating sediment from the North Sea at a rate which made the inter-tidal flat level keeping pace with sea level rise. The key question is, up to which rate of increased sea level rise the sediment accumulation in the Wadden Sea will be sufficient. This is a complex question since the sediment fluxes into the Wadden Sea depend on the rate of sea level rise itself, on other consequences of climate change as well as on sediment availability in a highly non-linear way.It is known that net sediment fluxes are driven by tidal asymmetries caused by non-linear overtides and horizontal density differences due to net-precipitation and run-off as well as cooling or heating of the Wadden Sea. The characteristics of non-linear overtides depend on sea level rise (more energetic tides, increased tidal range) and the horizontal density gradients may substantially alter with climate-related changes in precipitation/evaporation and cooling/heating. Furthermore, sediment fluxes are sensitive to wind intensity and direction, which are also susceptible to climate change. Although the knowledge about sediment dynamics in the coastal zone allows for realistic model simulations of sediment transport in the Wadden Sea, projections of morphodynamic change are still using highly simplified vertically integrated models. The knowledge gained from such models is therefore strongly limited.The leading objective of this project is therefore to assess possible morphological responses of the Wadden Sea to increased sea level rise and other aspects of climate change under conditions of changed sediment availability, using a process-based model. With this, the major driving forces for sediment transport in the Wadden Sea will be included. First, these simulations will be carried out in a systematic way using idealised bathymetries, identifying the most critical processes of morphodynamic change in the Wadden Sea. Using these bathymetries, impacts of sea level rise on the sediment accumulation can be assessed in combination with other changes of external forcing (precipitation-evaporation, cooling-heating, wind-wave forcing). In a second phase of the SPP, anticipating further increasing supercomputing capacities, these simulations will be carried out for realistic tidal basins in the Wadden Sea. In both phases, the dynamics of salt marshes will be explicitly included.