| Global climate change is a topic of major interest as the associated consequences could have a large impact on human societies. Computer models used to predict directions of future climate change are validated by means of retrospective analysis of past climate changes. Detailed reconstruction of past climates, especially temperature, is, therefore, of considerable importance. Several tools (proxies) are now available to reconstruct absolute sea surface temperatures. Continental temperature reconstructions, however, are hampered by a lack of quantitative temperature proxies and, consequently, are often qualitative rather than quantitative. Recently I developed a new quantitative terrestrial temperature proxy, the MBT index, which is based on the composition of fossil membrane lipids of soil bacteria. This index can be used to reconstruct continental, river basin-integrated, temperatures from a marine record in front of large river outflows. However, not all river fans contain enough terrestrial organic material or develop a continuous sedimentary archive to apply this method. In addition, several parts of the terrestrial realm will not be covered by this approach. Therefore, the use of this proxy has to be extended towards terrestrial sedimentary sequences like palaeosoils, lake sediments and peat bogs. In this VENI project I want to validate and apply this proxy in such systems. For example, it will be determined what the retention time is of the membrane lipids in soils before entering the lake and if similar membrane lipids are synthesised in lake sediments itself. MBT temperature reconstructions will be compared with other organic and inorganic proxies. This will ground-truth the use of the MBT-proxy in these settings and will lead to a better quantification of past temperature changes on land, and thus contribute to improvement of current climate models. |
