Das Projekt "Calibrating and validating scanning VIS Reflectance Spectroscopy data (380 - 730 nm) from minerogenic and biochemical varves: improving climate reconstructions from lake sediments" wird vom Umweltbundesamt gefördert und von Universität Bern, Geographisches Institut, Gruppe für Klimatologie,Meteorologie durchgeführt. Seasonal to annual quantitative reconstructions of spatially-explicit climate state variables for the last 2000 years across the world are recognized as one of the primary targets for current climate research. Varved (annually laminated) lake sediments play a key role in this context because they provide seasonally resolved paleoclimate archives with a very good chronology. The minerogenic varves in Lake Oeschinen, a proglacial lake in the northern Swiss Alps will be used to establish the first quantitative summer precipitation record back to ca. 1000 AD for Switzerland. In a pilot study for the varves AD 1920-1986, we have established that varve thickness and mineralogical composition is a good predictor for MJJA precipitation (r=0.64, p<0.05). Phyllosilicate influx is related to rain stroms whereas calcite influx is related to glacial meltwater. Novel scanning techniques (reflectance spectroscopy 380-730 nm) will be explored to analyze sediment compositions at very high (mm-scale) resolution.
Das Projekt "High-resolution climate reconstruction for phases of Holocene rapid climate change from lakes in Northern Europe: Assessing the potential of high-resolution non-destructive scanning techniques" wird vom Umweltbundesamt gefördert und von Universität Bern, Geographisches Institut, Gruppe für Klimatologie,Meteorologie durchgeführt. This project had two main goals: i) to test and further develop the novel method of scanning reflectance spectroscopy in the visible spectrum (VIS-RS) and ii) to gain improved insight into Holocene climate, especially into phases with rapid climate change by applying this method to sediments from lakes in Northern Europe. In a first study, we could confirm the high potential of VIS-RS for inferring for example organic content of lake sediments. We could as well demonstrate the high potential of multivariate calibration techniques for this purpose. In a next step it should be tested to which extend more time consuming and costly sediment parameters can be inferred by means of VIS-RS. In a second study, we analysed a comprehensive data set from a pro-glacial lake in Western Norway and extracted a signal of Holocene glacier variations from this data set. Focusing on the 8.2 ka event a period characterised by rapid cooling and subsequent warming in the North Atlantic realm, we find that the decomposition of the glacier happened even faster than the glacier advance. In this study, we applied a multitude of statistical methods to i) compare sediment parameters among each other, ii) to extract signals common to all sediment parameters and iii) to transform uncertainty of age-depth models into uncertainties of glacial activity. We therefore employed methods that are widely applied in palaeoecology but that have not found their way into the field of geochemistry and sedimentology yet.
Das Projekt "High-resolution climate reconstructions from varved Arctic lakes: exploring the potential and limits of non-destructive analytical techniques" wird vom Umweltbundesamt gefördert und von Universität Bern, Geographisches Institut, Gruppe für Klimatologie,Meteorologie durchgeführt. This project centered on the creation of a high-resolution climate reconstruction from Arctic lake sediments and investigation of the potential of high resolution scanning methods, in particular, reflectance spectroscopy. The most significant result was the development of a new approach to calibrate high-resolution biogeochemical measurements (e.g. reflectance spectroscopy or XRF scanning) by combining them with paleothermometer data (e.g. Alkenones or Tex86). This 'proxy-to-proxy' method is especially significant for the Arctic region where a 'calibration-in-time' technique cannot always be applied due to the short and sparse meteorological data network and the difficulties in precisely dating modern sediments. In this study scanning reflectance data from a lake in Western Greenland were calibrated using Alkenone data to create a new high-resolution 6000-year long temperature record. The resolution of the original temperature reconstruction was enhanced to resolve decadal to subdecadal changes, compared to an original multidecaldal to centennial resolution.