We quantify the change in extreme high sea level (ESL) statistics in the German Bight under rising \({{\mathrm {CO}}_2}\) concentrations by downscaling a large ensemble of global climate model simulations using the regionally coupled climate system model REMO-MPIOM. While the model setup combines a regionally high resolution with the benefits of a global ocean model, the large ensemble size of 32 members allows the estimation of high return levels with much lower uncertainty. We find that ESLs increase with atmospheric \({{\mathrm {CO}}_2}\) levels, even without considering a rise in the background sea level (BSL). Local increases of up to 0.5 m are found along the western shorelines of Germany and Denmark for ESLs of 20–50 years return periods, while higher return levels remain subject to sampling uncertainty. This ESL response is related to a cascade of an enhanced large-scale activity along the North Atlantic storm belt to a subsequent local increase in predominantly westerly wind speed extremes, while storms of the major West-Northwest track type gain importance. The response is seasonally opposite: summer ESLs and the strength of its drivers decrease in magnitude, contrasting the response of the higher winter ESLs, which governs the annual response. These results have important implications for coastal protection. ESLs do not only scale with the expected BSL rise, but become even more frequent, as preindustrial 50-year return levels could be expected to occur almost every year by the end of the century. The magnitude of the relative change in ESL statistics is hereby up to half of the expected rise in BSL, depending on the location. Changes in the highest extremes are subject to large multidecadal variations and remain uncertain, thus potentially demanding even further safety measures.

我们通过缩小使用区域耦合气候系统的大型全球气候模型模拟规模，量化了德国湾中\（{{\ mathrm {CO}} _ 2}}）浓度升高下的极端高海平面（ESL）统计数据的变化型号REMO-MPIOM。虽然模型设置将区域高分辨率与全球海洋模型的优势结合在一起，但32位成员的较大总体规模允许以较低的不确定性估算高回报水平。我们发现ESL随着大气\（{{\ mathrm {CO}} _ 2} \）的增加而增加甚至不考虑背景海平面（BSL）升高的情况。在德国和丹麦的西部海岸线上，对于20至50年回报期的ESL，局部增加了0.5 m，而更高的回报水平仍然受采样不确定性的影响。这种ESL响应与北大西洋风暴带沿线的大规模活动增强和随后的主要西风极端速度的局部增加有关，而主要的西北风道类型的风暴变得越来越重要。响应在季节上是相反的：夏季ESL及其驱动程序的强度在强度上有所降低，与较高的冬季ESL的响应形成对比，后者决定了年度响应。这些结果对沿海保护具有重要意义。ESL不仅会随着预期的BSL增长而扩展，但是，由于工业化前的50年回报水平到本世纪末几乎每年都会发生，因此变得更加频繁。因此，ESL统计数据的相对变化幅度最多为BSL预期上升幅度的一半，具体取决于位置。最高极值的变化会经历数十年的大变化，并且仍然不确定，因此可能需要采取进一步的安全措施。