NORTHERN NORWAY PALEOFIRE RECORDS REVEAL HUMAN IMPACTS ON REGIONAL FUELS AND FIRE ACTIVITY BEGAN C. 3500 YEARS AGO

Paleofire records demonstrate how Holocene fire activity in Fennoscandia varied in response to climate and human activities, offering insights into climate-fire relationships and the expected response of fire to anthropogenic climate change. The use of molecular biomarkers such as polycyclic aromatic hydrocarbons (PAHs) could expand on existing fire proxies, such as charcoal and fire scars, to resolve additional fire characteristics and reveal new trends. PAHs are a group of chemical compounds produced during the burning of organic matter that provide direct evidence of fire in the geologic record and preserve information about transportation and fuel source. This study combines multiple PAH records and a charcoal record derived from three lake sediment cores from the Lofoten Islands, Norway to provide a more comprehensive assessment of Holocene paleofire in northern Norway and contribute to the understanding of human impacts on fire activity in this region. All three lake sediment records show an overall increase in PAH accumulation rate over the past 7500 cal yr BP, ranging from 0 to 0.0463 μg/g/yr. Low values in the early Holocene (7500-3500 cal yr BP) reflect the natural fire signal driven by changes in climate prior to the influence of human activity. An abrupt increase in values, particularly low molecular weight PAHs, at c. 3500 cal yr BP that reach a maximum c. 2000 cal yr BP correlates with the initial establishment and expansion of human settlements and agriculture in Lofoten. The late Holocene (1000 cal yr BP-present) is characterized by a distinct increase reaching the highest values over the record, which reflects regional industrialization. Two charcoal size fractions were quantified (>125 μm and 63-125 μm) and support these trends. Alongside these reconstructions, trends in published paleofire data were compiled and re-evaluated to place the Lofoten records in context of broader Fennoscandia. These results have implications for understanding human influence on fire activity in Lofoten and for understanding connections between fire and climate.