Unraveling the signals of sea level and storminess of the past millennium (southern North Sea; SEASTORM)

我们建议解开区域海平面和北海南部的风暴在过去的千年和未来的全球变暖的信号。要检验的假设是，现有的基于代理的海平面重建承担了迄今为止低估的气候成分。为了解决这一假设，我们结合联合收割机高分辨率的代理数据，从活跃的盐沼和化石圩田沉积物与区域模型试验的结果，这有助于了解暴雨洪水变异性背后的相关机制，使我们能够估计气候变化下的暴雨洪水变异性的演变。具体而言，我们希望实现以下目标：1）生成过去一千年的相对海平面和风暴强度数据系列，2）评估当地风暴气候变化对基于代理的海平面重建的影响，3）验证基于代理的风暴强度数据系列，4）德国湾极端风暴洪水变化的量化及其相关强迫机制的研究，5）未来全球变暖下极端暴雨洪水变率的估算; 6）现代盐沼环境对区域海平面和气候变化的响应调查。
代理和模型方法将共同关注暴雨洪水变率和相关驱动因素。将在自然生长的盐沼中采集过去世纪的沉积物的芯。将进一步评估中世纪到近代早期圩田的化石沼泽沉积物。详细的沉积学和地球化学数据将有助于重建沉积环境和确定风暴潮层。有孔虫传递函数的应用将提供关于相对于潮汐框架的相对高程和淹没变化的信息。替代研究将得到区域地球系统模型实验的补充，这些实验将调查北海在过去一千年中选定的时间间隔内的气候变化和风暴频率。这些数据将用于研究德国湾极端海平面变化的十年变化与相关的大尺度气候变化之间的关系。在上一个千年的模拟中发现的巨大的极端值变化表明，估计未来海平面极端值的标准方法并没有考虑到它们的全部变率谱，典型的集合大小不足以将信号与噪声分开。因此，我们将采用一个大的集合方法来估计极端海平面统计数据的未来变化，允许检测潜在的气候变化信号。 
我们的项目将提供第一次尝试重建的强迫机制和沿海影响的海平面变化和风暴的北海南部直接结合代理数据从沉积物档案和气候模拟信息。

We propose to unravel the signals of regional sea level and storminess of the southern North Sea during the past millennium and under future global warming. The hypothesis to test is that existing proxy-based sea-level reconstructions bear a so far underestimated climate component. In order to address this hypothesis we combine high-resolution proxy data from active salt marshes and fossil polder deposits with results from regional model experiments, which help to understand the relevant mechanisms behind storm flood variability and allow us to estimate the evolution of storm flood variability under climate change. Specifically we want to address the following objectives: 1) Generation of data series of relative sea level and storminess of the past millennium, 2) Evaluation of the impacts of shifts in local storm climate on proxy-based sea-level reconstructions, 3) Validation of the proxy-based data series of storminess, 4) Quantification of extreme storm flood variability in the German Bight and investigation of their associated forcing mechanisms, 5) Estimation of extreme storm flood variability under future global warming, and 6) Investigation of the response of modern salt marsh environments to regional sea-level and climate change.
Both proxy and model approaches will jointly focus on understanding storm flood variability and associated drivers. Sediments of the past century will be cored in naturally grown salt marshes. Fossil marsh sediments from medieval to early modern polders will be further evaluated. Detailed sedimentological and geochemical data will allow for reconstruction of the depositional environments and for the identification of storm-surge layers. Application of a foraminiferal transfer function will deliver information on relative elevation and submergence changes with respect to the tidal frame. The proxy studies will be complemented by regional Earth System Model experiments investigating the climate variability and storm frequency of the North Sea for selected time intervals of the past millennium. These data will be used to study the relationships between decadal variations of extreme sea-level variability in the German Bight and associated large-scale climate variations. The large extreme value variations found in the last millennium simulations have shown that the standard approach to estimate future sea-level extremes does not account for their full variability spectrum and the typical ensemble size is not sufficient to separate signal from noise. We will therefore employ a large ensemble approach to estimate future changes in extreme sea-level statistics, allowing the detection of a potential climate change signal. 
Our project will provide the first attempt to reconstruct the forcing mechanisms and coastal impacts of sea-level variability and storminess of the southern North Sea by directly combining proxy data from sediment archives and climate modeling information.