oa Boreal Forest Fires Recorded in 3000 Yrs Arctic Delta Sediments

Boreal forest fires are an important component of the vegetation and carbon dynamics in the Arctic. Increased temperature triggered by anthropogenic climate change is intensifying the number and scale of spring and summer boreal fires. High resolution sedimentary archives hold the key to reconstruct reliable records of past biomass burning. We studied a 3 m-long piston core, and its corresponding multicore, located in the Beaufort Sea, in front of the Mackenzie River mouth (Arctic Canada). The core captures a 3000-yrs history of discharge from the Mackenzie River catchment and eolian input. Biomass-burning biomarkers (benzene polycarboxylic acids, BPCA1, and levoglucosan2,3, created during low-temperature biomass-burning) as well as microscopic charcoal (larger than 10 µm)4,5 were quantified to reconstruct past variation in boreal fires. They are linked to changes in vegetation reconstructed using pollen and biomarkers (lignin phenols). The combined information from multiple biomass burning proxies provide a unique late Holocene record of boreal fire activity in Arctic Canada, recording climatic events such as the Little Ice Age.