[Dietze] Siberian fire regime shifts during interglacials of the last 3.6 Myrs inferred from sedimentary records of Lake El’gygytgyn (NE Asia)
German Title: Siberian fire regime shifts during interglacials of the last 3.6 Myrs inferred from sedimentary records of Lake El’gygytgyn (NE Asia)
Current Status: approved
Main Applicant:Dr. Elisabeth Dietze
Begin: 1 March, 2021
Conveyor Duration: 12
Predicting and adapting to the impacts of ongoing and future climate change for society requires a deep understanding of internal natural feedbacks on the earth surface beyond the influence that humans exert on natural ecosystems. The boreal and tundra biomes are especially sensitive to climate change and play a fundamental role in global biophysical and biogeochemical cycles, for example via their fire regime. However, the long-term feedbacks between fire, vegetation and climate are largely unknown, especially from the high latitudes, although long-term natural variability strongly influences short-term variability. Highly uncertain is, if and how currently increasing temperatures over the Arctic would lead to biome shifts that are accompanied by shifts in fire regimes.
Hence, the proposed project will study northeastern Siberian fire regime shifts during multiple Plio-Pleistocene interglacials using the only continuous sedimentary record covering the last 3.6 Myrs, i.e., from Lake El’gygytgyn (ICDP Site 5011-1). Focusing on interglacials of different strengths (maximum temperature) and of different biome configurations (tundra, summergreen boreal or evergreen boreal forest), I aim to answer the timely questions on what drove long-term shifts in fire regimes in higher latitudes - climate or vegetation, and which internal fire-permafrost erosion feedbacks stabilized or destabilized vegetation types. Regional fire regimes will be reconstructed using (i) microscopic charcoal influx as proxy for high-intensity fires that are characteristic for modern evergreen boreal forest, and, from the same samples, (ii) the new sedimentary proxy for low-temperature fires - the monosaccharide anhydrides levoglucosan and its isomers. These biomarkers represent biomass combustion as in surface fires, which are frequently occurring in modern summergreen boreal larch forests. To determine the drivers of fire regime shifts, fire records will be statistically compared with vegetation reconstructions from pollen records and independent climate reconstructions from the same site and global compilations. To assess, if frequent fires affected permafrost degradation and sediment erosion, the fire records will be statistically compared with regional and local erosional proxies derived from new grain size data evaluations using end-member modelling. The proposed sampling and analysis strategy will allow robust and quantitative comparisons beyond the absolute age uncertainties. Hence, the project will contribute a new understanding of timescale-dependent feedbacks between climate, fire, vegetation and permafrost providing the long-term baselines for current environmental change.