| Understanding the past climate change is quite literary the key to understanding future climate change. Testing climate models for future climate change critically depends on our ability to reconstruct paleo-climate change and its impact on the environment. To this day, paleosalinity remains one of the most important oceanographic parameters which can not be reconstructed with reasonable accuracy based on sedimentary records. Currently paleosalinity is estimated using a combination of oxygen isotopes (delta18O) of the tests of pelagic foraminifera and paleo-temperature reconstructions to calculate the delta18O of the original seawater. The major difficulty with this method is the in space and time variable delta18Owater-salinity relationship making paleosalinity reconstructions very tentative. An alternative method is using the hydrogen isotopic composition of algal and bacterial biomarker lipids to reconstruct paleosalinity since the hydrogen isotopic fractionation of phototrophic organisms depends heavily on salinity. My initial results showed that the hydrogen isotopic composition of algal derived long-chain alkenones is a promising tool for paleosalinity reconstructions. In this VIDI project I propose to further develop and validate this paleosalinity proxy and extend it for a range of other algal and bacterial lipids through culture studies. I will also develop a more qualitative paleosalinity reconstruction method based on specific biomarker lipid distributions such as the tetra-unsaturated C37 alkenone and the C20/C25 diether membrane lipid derived from halophilic archaea. The different qualitative and quantitative salinity proxies will be validated in environmental settings with large salinity gradients. Finally, these novel proxies will be applied to different paleo settings ranging from Holocene Norwegian fjords to Paleocene-Eocene and Cretaceous green house worlds in combination with more established proxies as part of a multiproxy approach. |
