Relationships between Baltic Sea level variations and periods of rapid climate change in the Holocene as analogues for future changes

将通过对长期仪器序列、代理数据和全球气候模式模拟的联合分析来估计近8000年来由快速气候变化引起的波罗的海海平面变化。总体目标是找到过去记录中海平面快速变化的类似物，用于估计未来几个世纪的变化。1)全新世全球气候模式ECHO-G的全球气候模拟输出将使用标准统计降尺度方法进行区域化，该方法将气象强迫（风、温度、降雨）和海平面变化联系起来，并对每个单独的海平面测量仪的过去和未来的海平面变化进行模拟的空间海平面变化估计。这些统计模型已经在SINCOS项目中进行了设计和验证。这些模拟将使我们能够确定过去的一些时期，在这些时期，气候强迫可能导致海平面变化的速度与本世纪预计的一样快。2)对波罗的海南岸活栎树年轮数据的分析将验证过去与气候有关的海平面变化的估计。在与近一个世纪众所周知的气候进行校准后，气候信号也可以从波罗的海南部海岸的长期橡木年表中获得，这些年表由几个绝对确定的年份组成，以及过去8000年的一些浮动部分。可以设计统计模式，以类似气象资料和海平面资料的方式描述代理资料-气候强迫-海平面之间的间接关系（SINCOS项目）。然后可以将统计模型应用于长时间序列的气候代理数据，如树木年轮序列，以获得与气候有关的海平面变率的第二次独立估计。将特别关注过去一千年的年代际冷期、1700年左右的晚蒙德极小期和1800年左右的道尔顿极小期。在后一阶段，对气候变化和仪器海平面变化的直接分析可能成为可能。根据一项科学服务合同，我们将对树木年轮数据进行分析，并将分析结果交给我们处理。3)北大西洋全新世气候经历了年代际和百年尺度的气候突变期，如所谓的82k事件。在短短几十年的时间里，格陵兰岛的气温可能下降了5度，北欧的气温下降了2度，在几个世纪的时间里恢复到正常水平的速度较慢。这种突然而强烈的气候变化，可能是由北大西洋经向翻转环流的重组引起的，可以看作是未来变化的类似物，因为全球气候模式也预测了未来经向翻转环流的减弱。全球气候模式ECHO-G将与区域模式REMO一起用于模拟8.2K事件及其对波罗的海海平面可能产生的影响。对长时间序列的树木气候学数据进行分析，将为该地区的区域气候影响提供线索。这些结果可以与文献中的替代海平面指标或本集群的其他项目获得的海平面指标进行比较。

Variations of Baltic Sea level caused by rapid climate change within the last 8000 years will be estimated from joint analysis of long instrumental series, proxy data and simulations with global climate models. The overall goal is to find analogues for rapid sea-level changes in the past record that can be used to estimate changes in the next centuries. 1) The output of global climate simulations with the global climate model ECHO-G for the Holocene will be regionalized with standard statistical downscaling methods, which relate meteorological forcing (wind, temperature, rainfall) and sea-level variations yielding - together with the simulated steric sea-level variationsestimations of the past and future variations of sea-level for each individual sea-level gauge. These statistical models have been already designed and validated in the project SINCOS. The simulations would allow to identify periods in the past where the climate forcing may have produced sea-level changes as rapid as those expected in this century. 2) The estimations of past climate-related sea-level changes will be validated by the analysis of tree-ring data from living oaks along the southern coast of the Baltic Sea. After calibration with the well-known climate during the recent century, the climatic signal can be expected to be also retrievable from the long-term oak chronology along the southern coast of the Baltic Sea composed of several absolutely dated as well as some floating parts over the last 8.000 years. Statistical models may be designed that describe the indirect relationship proxy data - climate forcing - sea level in a similar manner as meteorological data and sea-level data (project SINCOS). The statistical models can be then applied to the long time series of climatic proxy data, such as tree-ring series, to obtain a second and independent estimation of the climate-related sea-level variability. Particular attention will be posed on decadal cold periods in the past millennium, the Late Maunder Minimum around 1700 and specially the Dalton Minimum around 1800. In the latter period a direct analysis of climate change and instrumental sea-level change may be possible for a number of gauges. The analysis of tree-ring data will be performed and the results put at our disposal by a contract for scientific services. 3) The North Atlantic Holocene climate has undergone periods of abrupt climate change at decadal and centennial timescales, e.g. the so-called 8.2k event. Temperatures in Greenland may have dropped by as much as 5 degrees and those in Northern Europe by 2 degrees in a period as short as a few decades, with a slower recovery to normal values along a few centuries. This sudden and strong climate change, probably caused by reorganizations of the Meridional Overturning Circulation in the North Atlantic, could be seen as an analogue for future changes, since global climate models also predict a future weakening of the Meridional Overturning Circulation. The global climate model ECHO-G, together with the regional model REMO, will be used to simulate the 8.2K event and its possible consequences for Baltic Sea level. The analysis of long time series of dendroclimatological data will deliver clues about regional climate impacts in this area. These results can be compared to proxy indicators of sea level from the literature or obtained by other projects of the present cluster.