Reconstructing Changes in Regional Hydrology during the Holocene employing Novel Stable Isotope and Molecular Proxies

大陆水文循环对全球气候变化作出反应的时间和规模仍未得到很好的了解。特别是全新世期间的突然气候变化，通常通过大陆上的水文变化表现得最严重。然而，在试图预测人为气候变化对水文过程的影响时，了解这些过程及其原因是至关重要的。由于缺乏直接的水文指标和古气候记录，陆地水文系统的区域响应差异在很大程度上是未知的。近年来出现了一种有希望的新的古水文学替代物--单个类脂生物标志物的氢同位素组成，它能够增强我们对大陆水文学变化的了解。因此，我建议成立一个艾美诺特研究小组，目标如下：(1)通过全面的校准研究，推进和完善脂质生物标志物氢同位素测量作为陆地生态系统古水文指标的使用。通过对控制温室条件下的植物以及沿陡峭(自然)水文梯度的植物和土壤的研究，我们将能够了解除源水同位素组成外，影响陆地植物来源类脂的氢同位素组成的因素。这项工作将充分确立利用类脂生物标记物氢同位素作为陆地生态系统可行的古水文学替代物。(2)从温带、干旱和高度季节性的气候状况获得全新世降水、植物蒸散量和大气环流变化的高分辨率记录。通过对整个全新世优秀的陆相气候档案、玛尔湖进行化合物特定同位素分析，我们将能够确定区域水文变化的时间和大小。我们将比较不同气候平均状态(温带、干旱和季风气候状况)下，这一新指标对水文学变化的反应。将特别重视气候突变期间降水和蒸散量变化的性质和时间，例如中欧的年轻仙女座。我们的工作还将更好地限制由于热带季风模式的变化而导致的降水变化，这一地区将受到人为气候变化导致的水文变化的最严重影响。这里提出的工作成果将大大增强我们对整个全新世大陆古水文学变化的了解，并建立一个新的古水文学指标在古气候界中的使用。

The timing and magnitude of the response of the continental hydrological cycle to global climate changes is still not well understood. Especially abrupt climatic change during the Holocene is often most severely expressed through changes in hydrology on the continents. Knowledge of these processes and it’s causes however, is essential, when trying to predict the consequences of anthropogenic climate change on hydrological processes. Differences in regional responses of the terrestrial hydrological system are largely unknown due to a lack of direct hydrological proxies and paleoclimate records. A promising new paleohydrological proxy, the hydrogen isotopic composition of individual lipid biomarkers, has been emerging in the last years, which is capable of enhancing our knowledge about changes in hydrology over the continents. Therefore, I propose to establish an Emmy Noether Research Group with the following aims: (1) Advance and refine the use of lipid biomarker hydrogen isotope measurement as a paleohydrological proxy for terrestrial ecosystems through comprehensive calibration studies. Through studies on plants under controlled greenhouse conditions as well as of plants and soils along steep (natural) hydrological gradients, we will be able to understand the factors influencing the hydrogen isotopic composition of terrestrial plant derived lipids – apart from the source water isotopic composition. This work will fully establish the use of lipid biomarker hydrogen isotopes as a viable paleohydrological proxy for terrestrial ecosystems. (2) Obtain high-resolution records of changes in precipitation, plant evapotranspiration and atmospheric circulation throughout the Holocene from temperate, arid and highly seasonal climatic regimes. By applying compound-specific isotope analysis to excellent continental climate archives, maar lakes, throughout the Holocene we will be able to determine the timing and magnitude of regional hydrological changes. We will compare the response of this new proxy to changes in hydrology for different climate mean states (temperate, arid and monsoonal climate regimes). Special emphasis will be placed on the nature and timing of precipitation and evapotranspiration changes during abrupt climate transitions, such as the Younger Dryas in Central Europe. Our work will also provide better constraints on variations in precipitation as a consequence of changing monsoonal patterns in the Tropics, a region which will most harshly effected by changing hydrology through anthropogenic climate change. The outcome of the work proposed here will significantly enhance our knowledge about changes in continental paleohydrology throughout the Holocene as well as establish the use of a new paleohydrological proxy within the paleoclimate community.