Evaluation of the potential of speleothems for reconstruction of (short-term) phases of extreme climate

这项建议的目的是评估洞穴在重建过去(短暂的)阶段和极端气候事件，如特别低温、极端降雨量或极高风速方面的潜力。此类极端事件很少发生，但往往造成巨大破坏，可能对有关地区的人口和生态系统造成严重后果。更好地了解这类极端事件的原因和边界条件将有助于改进对未来极端事件发生的预测，这对于对人口的后果作出适当安排至关重要。洞穴化石提供精确年代的多代理记录，分辨率接近年度，因此作为此类事件的档案具有很大潜力。然而，洞穴上方含水层中记录的洞穴中的代理信号在一定程度上得到了平滑。因此，需要评估不同洞穴系统和洞穴喷发系统在重建过去极端事件方面的敏感性。这项提议的重点是8.2ka事件和过去2000年。8.2ka事件是全新世最极端的气候异常，反映了间冰期气候状态期间淡水戏剧性地涌入北大西洋的影响。在过去的2000年里，发现了几次百年尺度的气候振荡(如中世纪暖期和小冰期)。除了这些事件外，还观察到了其他短暂的气候异常，例如公元1342年7月历史性的圣马格达勒洪水或公元150年史无前例的欧洲高温和干旱。一些事件是由火山喷发引发的，例如公元1816年没有夏天的一年，这与公元1815年的坦博拉喷发有关。包括8.2 ka事件和德国三个洞穴系统过去2000年的洞穴在内的几个洞穴遗迹都是可用的。对于所有三个洞穴，都建立了长期的洞穴监测计划，这是了解洞穴系统中发生的过程和解释洞穴中记录的代理信号的先决条件。我们将以很高的分辨率(~每年)对石笋相应剖面中的稳定同位素和微量元素进行分析，并用MC-ICPMS 230Th/U测年来精确测定样品的年龄。将利用基于气象和洞穴监测数据的定量正演模拟方法，确定最适合重建过去短期极端事件的指标。精确确定日期的高分辨率多指标记录和定量正演模拟方法的结合为(1)确定重建过去短期极端事件的最合适指标和(2)比较不同洞穴中的具体事件提供了坚实的基础。这将允许确定事件的时间、持续时间和结构。

The objective of this proposal is to evaluate the potential of speleothems for reconstruction of past (short-lived) phases and events of extreme climate, such as particularly low temperatures, extreme amounts of rainfall or very high wind speed. Such extreme events occur rarely, but they often cause great damage, which may have serious consequences for the population and ecosystems of the concerned region. A better understanding of the causes and boundary conditions of such extreme events will enable an improved prediction of the occurrence of future extremes, which is essential to make appropriate arrangements for the consequences for the population. Speleothems offer precisely dated multi-proxy records with near annual resolution, and consequently have great potential as archives of such events. However, the proxy signals recorded in speleothems are smoothed to a certain extent in the aquifer above the cave. Thus, the sensitivity of different cave systems and speleothem proxies for reconstruction of past extreme events needs to be evaluated. The focus of this proposal is on the 8.2 ka event and the last 2000 years. The 8.2 ka event was the most extreme climate anomaly of the Holocene and reflects the impact of dramatic freshwater influx into the North Atlantic during an interglacial climate state. During the last 2000 years, several centennial scale climate oscillations (e.g. the Medieval Warm Period and the Little Ice Age) were identified. In addition to these events, other, short-lived climate anomalies were observed, such as the historic St. Magdalenes flood in July 1342 AD or the unprecedented European heat and drought of 1540 AD. Some events were triggered by volcanic eruptions, such as the year without summer in 1816 AD, which was related to the Tambora eruption in 1815 AD. Several speleothems including the 8.2 ka event and the last 2000 years from the three cave systems in Germany are available. For all three caves, long-term cave monitoring programs have been set up, which is a prerequisite to understand the processes occurring in the cave systems and to interpret the proxy signals recorded in the speleothems. We will analyse both stable isotopes and trace elements in the corresponding sections of the stalagmites at very high resolution (~annual), and precisely date the samples by MC-ICPMS 230Th/U-dating. The identification of the most suitable proxies for reconstruction of past short-term extreme events will be performed using a quantitative forward modelling approach based on meteorological and the cave monitoring data. The combination of precisely dated high-resolution multi-proxy records and a quantitative forward modelling approach provides a solid base in order to (i) identify the most suitable proxies for reconstruction of past short-term extreme events and (ii) compare specific events in different speleothems. This will allow the determination of the timing, duration and structure of the events.