Global climate change is a topic of major interest as it has 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 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, my group discovered a new quantitative continental temperature proxy, the MBT index, which is based on the distribution of membrane lipids of soil bacteria. Their composition is a function of annual mean air temperature (MAT). These lipids are transported by rivers to the ocean and deposited in marine sediments. Determination of the MBT index in cores from river fans can, thus, potentially be used to reconstruct continental, river basin-integrated, temperatures from a marine record in front of large river outflows. We will study the mechanisms of transport of the soil bacterial membrane lipids to the ocean in many river systems and compare the down-core changes in their composition with conventional MAT proxies. We will also investigate the potential of lake sediments as archives of continental climate change using our new MBT palaeothermometer and apply this thermometer in the assessment of continental climate change during the transition from a hothouse to an icehouse Earth in the last 100 million years. This project that combines aspects of microbiology, molecular ecology, lipid biogeochemistry and paleoclimatology will bring this novel continental palaeothermometer to maturity. If we can ground-truth the use of the MBT-proxy, it will open up new windows in palaeoclimatological research and thus contribute to improvement of current climate models.
Fields of science
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