BURNING IN BERINGIA – GLACIAL-INTERGLACIAL WILDFIRE VARIABILITY AT LAKEEL’GYGYTGYN

Arctic tundra fires have the potential to release large amounts of permafrost soil carbon into the atmosphere as carbon dioxide. Understanding the environmental controls of tundra fires is therefore essential for predicting future climate feedbacks from burning. Aridity, lightning frequency, and vegetation assemblages are key factors affecting the frequency and severity of tundra wildfires. For example, the Last Glacial Maximum was cold and dry in parts of the Arctic, and wildfires were more common than during the relatively warm and moist Holocene. Contrastingly, current warming and moistening appear to be moving the Arctic into a more fire-prone climatic state.

Paleoclimate records of past warm periods are needed to elucidate if future climate change will ultimately suppress or stoke tundra fire activity. Here, we investigate molecular proxies of fire and climate across Marine Isotope Stages (MIS) 20-22 (860-720 ka) in the Lake El’gygytgyn drillcore from NE Russia. Fire activity is reconstructed using a combination of polycyclic aromatic hydrocarbons (PAHs) and monosaccharide anhydrides (MAs), while temperatures are reconstructed using branched glycerol dialkyl glycerol tetraethers, and vegetation change is inferred from leaf wax n-alkanes and pollen assemblages.

We find that MIS 20-22 experienced large climatic and vegetation shifts at Lake El’gygytgyn. Interglacial stage MIS 21 is approximately 4-6 °C warmer than the preceding and following glacial periods. Tundra and cold steppe biomes characterize the study interval, but there are periods with elevated deciduous and coniferous tree species as well. We use the PAH and MA ratios to determine fire biomarker source regions and source fuel types across this glacial-interglacial cycle and further discuss how the wildfire proxies vary in response to environmental change.