Variability of concentrations and size distributions of black carbon particles in Northeast Greenland since the Industrial Revolution

Black carbon (BC) is a crucial component among light-absorbing aerosols, significantly impacting Earth's radiation budget. BC in the atmosphere absorbs sunlight and leads to atmospheric heating, while BC deposited on snow and ice surfaces reduces albedo, accelerating snowmelt. Additionally, BC can serve as cloud condensation nuclei and ice nucleating particles. Understanding the historical role of BC in pristine environments, particularly in the Arctic, where climate and environmental changes have been pronounced, is vital. However, data on preindustrial BC levels remain sparse, with limited observations unaffected by anthropogenic sources. Ice cores offer valuable proxy records of BC concentrations and size distributions since the preindustrial era. In this study, we analyzed an ice core retrieved from the EastGRIP site in Northeast Greenland, reaching a depth of 133 meters, using a Continuous Flow Analysis (CFA) system at the National Institute of Polar Research. The CFA system facilitated high-resolution data collection on BC, stable isotopes of water, microparticles, and eight elements (Na, Mg, Al, Si, S, K, Ca, Fe). For BC analysis, we employed a recently developed Wide-range (WR) SP2 (Single Particle Soot Photometer) capable of detecting BC particles in the size range of 70 to 4000 nm. The combination of WR-SP2 and a high-efficiency nebulizer enabled precise measurements of BC concentrations and size distributions. The core was dated through annual layer counting primarily using Na concentrations, supplemented by microparticle and Ca concentrations. As reference horizons, we used volcanic sulfate peaks and tritium peaks from nuclear bomb testing. We present the EastGRIP BC record spanning the past 350 years and compare it with previously obtained BC records from Greenland. Our findings reveal that both the number and mass concentrations of BC at EastGRIP began to increase around 1860, driven by the influx of anthropogenic BC. These concentrations peaked around 1920 and have since declined. While this temporal trend aligns with other Greenland sites, it differs slightly from that observed in southern Greenland, potentially reflecting variations in emission source contributions between northern and southern Greenland. Notably, anthropogenic BC at EastGRIP exhibited larger sizes than biomass-burning BC, consistent with previous findings for the SIGMA-D site in Northwest Greenland. In the preindustrial period, BC concentrations showed their peak during summer. However, the inflow of anthropogenic BC has shifted the peak season from summer to winter/early spring. Unlike SIGMA-D, the BC peak season did not revert to summer in the 1990s. Our accurate, high temporal-resolution data on BC concentrations and sizes offer crucial insights into understanding BC sources, transport pathways, and deposition processes. Furthermore, this new dataset serves to constrain and validate aerosol and climate models, ultimately improving projections for future climate and environmental conditions.