Biomass burning over the past 350 years: insights from high-resolution analysis of black carbon particles in a northwestern Greenland ice core

Black carbon (BC) particles, emitted by incomplete combustion of biomass and fossil fuels, play a crucial role in Earth's radiation budget and climate. Conversely, climate changes can influence BC emissions from biomass burning (BB). Global warming has been linked to the recent increase in large wildfires worldwide, causing significant ecological and societal damage. Increased occurrence of large wildfires in the future could affect Earth’s radiation budget, and change the frequency at which certain regions are exposed to serious hazards. Understanding the long-term changes in BC concentrations and size distributions is essential to assess BC's role in climate dynamics and its response to climate change. At the EGU 2024 General Assembly, we presented an ice core BC record from the EastGRIP site in northeastern Greenland, focusing on temporal variability in BC derived from anthropogenic emissions. In this study, we present a high-resolution BC record from the SIGMA-D ice core in northwestern Greenland, spanning the past 350 years. Using an improved BC measurement technique coupled with a continuous flow analysis (CFA) system, we obtained accurate, high-temporal-resolution data on BC particle size and mass/number concentrations.

Our results reveal that both BC number and mass concentrations began to increase in the 1870s, peaked during the 1910s–1920s due to the inflow of anthropogenic BC, and subsequently decreased to pre-industrial levels or lower. However, BC particle size did not return to pre-industrial values, remaining elevated during the 1960s–2000s. Anthropogenic BC emissions also shifted the annual peak in BC concentrations from summer to winter–early spring, while the peak returned to summer after BC concentrations declined to pre-industrial levels. This suggests that BB has become the dominant source of BC at the SIGMA-D site in recent years. Interestingly, anthropogenic BC emissions made only a minor contribution to summer BC concentrations throughout the past 350 years. By separating winter and summer BC data, we reconstructed temporal variations in BC originating from boreal forest fires, even during periods of significant anthropogenic input. Our findings indicate no increase in boreal forest fire-derived BC until the early 2000s. These results enhance our understanding of the interplay between natural BC emissions, anthropogenic influences, and climate variability since the preindustrial time.