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, we 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 sediment 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. This concept needs to be further tested in geographically contrasting settings before it can be applied with confidence.
Here, we perform a detailed study on the sources of soil GDGTs, mode of transport, and deposition in the Yenisei River and Kara Sea (Arctic Ocean) system. The Yenisei is one of the largest rivers in the world and its drainage basin covers different climatic zones and biomes (tundra, taiga/boreal forest). We sample soils from the drainage basin, river particulate matter, and river and Kara Sea sediments and analyze them for GDGTs. This provides detailed insight in how the climate signal stored in the composition of soil GDGTs are transported to the ocean and how mixing and diagenetic processes affect this. We also study the radiocarbon age of the soil GDGTs transported to the ocean and study Holocene changes in the delivery of these components to the shelf of the Arctic Ocean. Ground-truthing the use of the MBT-proxy opens up new windows in palaeoclimatological research and thus contributes to the improvement of current climate models.