Influences of high reliefs on isotope hydrology and coupled climate proxies

点击翻译按钮获取中文摘要

Climate proxies such as tree rings rely on stable isotope ratios for the reconstruction of palaeoclimatic conditions. Such information then allow the calibration of models that evaluate and predict ongoing and future effects of global climate change. According to model predictions, the western Mediterranean is a region that will face severe climatic changes. Therefore, the island of Corsica in that region has been the target for palaeoclimate reconstructions by means of dendrochronology and stable isotopes. However, the oxygen stable isotope results from Corsican pines could not yet be interpreted satisfactorily. The oxygen stable isotope values (delta18O) of tree rings mainly depend on the oxygen isotope ratio of local precipitation and soil water. The precipitation delta18O values vary according to temperature, altitude and the moisture source area. Such parameters are determined nowadays rather precise but need to be assumed for the past. An important isotope effect is the so-called altitude effect that describes the relation of the delta18O value of precipitation and altitude. The large global network of isotopes in precipitation (GNIP) database of the International Atomic Energy Agency (IAEA) allows for a good regional estimate of isotope effects. However, things become more difficult in regions with high and steep mountain reliefs. Some latest publications suggest that the altitude gradient is absent in such regions during specific seasons. The reason for that observation could be seasonal height variations of the atmospheric planetary boundary layer (PBL). This isotope hydrology proposal is part of the project package CorsicArchive that also consists of interlinking proposals for climate, dendroisotopes and dendroecology. It is planned to install and regularly sample nine isotope precipitation samplers along an east-west altitudinal transect. This proposal will specifically explore the dynamics of the PBL and the isotope altitude effect. Additional questions relate to moisture source of air masses and the local moisture recycling within the islands hydrologic cycle. Furthermore, soil water and surface water analyses are planned to trace and quantify changes of the delta18O values along the pathway of water to the tree rings. The approach of this proposal aims to fill the gaps in the current knowledge of isotope hydrology of high reliefs and will finally lead to a more robust interpretation of related climate proxies in a climate change sensitive region. With respect to the current climate change, it is essential to understand climatic variations and its triggers in the past to better predict future changes.