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的响应时间和幅度仍未得到很好的了解。尤其是全新世的气候突变，往往最严重地表现在大陆的水文变化上。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必不可少的。由于缺乏直接水文代用物和古气候记录，陆地水文系统的区域响应差异在很大程度上是未知的。近年来出现了一种新的古水文指标——单个脂质生物标志物的氢同位素组成，它能够增强我们对大陆水文变化的认识。因此，我建议成立Emmy Noether研究组，其目标如下：(1)通过全面的定标研究，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应用。通过对受控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，影响陆生植物源性脂质的氢同位素组成的因素。这项工作将充分建立脂质生物标志物氢同位素作为陆地生态系统可行的古水文代理的使用。(2)从温带、干旱和高度季节性的气候条件下获得整个全新世降水、植物蒸散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大陆气候档案、马尔湖进行化合物特异性同位素分析，我们将能够确定区域水文变化的时间和幅度。我们将比较这个新的代理对不同气候平均状态（温带、干旱和季风气候）的水文变化的响应。将特别强调气候突变期间降水和蒸散变化的性质和时间，例如中欧的新仙女木期。我们的工作还将更好地限制由于热带季风模式变化而导致的降水变化，热带地区将受到人为气候变化引起的水文变化的最严重影响。本文提出的研究结果将大大提高我们对整个全新世大陆古水文变化的认识，并在古气候群落中建立新的古水文代理。

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.