Titel: Reconstructing climate and environmental changes from the Lateglacial to modern times from lake and peat sediments
Speaker: Minna Väliranta, Environmental Change Research Unit (ECRU), Ecosystems and Environment Research Programme, University of Helsinki, Finland
Time & place: March 4 at 11h00–12h00, Ahlmann Hall, Geoscience Building

Lunch sandwich will be served after the seminar. Please e-mail annika.granebeck@su.se, latest March 2 if you would like one. Welcome!

Part I: Lake sedimentary archives contain, in the form of macroscopic and microscopic plant remains, valuable information of past climate and associated changes in floral communities. Sedimentary pollen assemblages have been the traditional way to quantitatively reconstruct past climate. While this approach typically neglects taxa that occur in small proportions in pollen records, namely many local non-arboreal taxa, recent methodological development in applying macroscopic fossil plant remains data has allowed quantitative estimations of past temperatures based on local and rare taxa. The new approach shows that warming at the Late glacial-Holocene transition happened earlier with considerably higher summer temperatures than traditional estimates. The new results are consistent with much higher orbital summer insolation.

Part II: Peatlands act as an integral global biogeochemical agent. Recent modelling studies predict that due to warming northern peatlands will act as an increasingly effective carbon sink over the next century. However, other studies suggest widespread drying of European peatlands. These scenarios partly override each other. Our data from subarctic peatlands suggest drying over the recent decades and increased carbon accumulation rate.