FY 2025

Sensitivity of wintertime Arctic black carbon to removal processes and regional Alaskan sources

Ioannidis, E., K.S. Law, J.-C. Raut, L. Marelle, O. Tatsuo, E. Andrews, S. Ohata, T. Mori, S. Morris, Y. Kondo, S. Sarma, K. Eleftheriadis, Z. Klimont, A. Soulie, S. Darras, C. Granier, P.K. Quinn, and K.A. Pratt

J. Geophys. Res., 130(7), e2024JD042885, doi: 10.1029/2024JD042885, View open access article at AGU/Wiley (external link) (2025)

Air pollutants are primarily transported from midlatitude emission regions in winter and early spring, leading to elevated concentrations of aerosols, including black carbon (BC), in the Arctic, a phenomenon known as Arctic haze. The Weather Research and Forecasting model coupled with chemistry is used to investigate potential causes of uncertainties in modeling Arctic BC for winter 2014. The model captures observed variability in BC at surface sites, reproducing BC concentrations at Zeppelin but showing a low bias at Tiksi, Alert, and Utqiaġvik/Barrow. The influence of removal processes on model BC biases is explored by switching off dry or wet deposition. Wet deposition, during transport in the North Atlantic storm track, and locally over Svalbard, dominates BC removal at Zeppelin, while wet removal in the Pacific storm track influences BC at Alert and Utqiaġvik/Barrow. Dry removal over Asian source regions and Alaska affects BC at Utqiaġvik/Barrow, and is larger than wet removal at Tiksi due to the proximity of local/regional anthropogenic sources. Regional runs over northern Alaska in late January show improved simulated BC compared to observations at Utqiaġvik/Barrow, in part, due to better resolution of removal processes, and local/regional emissions. Sensitivity runs also show that regional Alaskan sources, notably from the North Slope of Alaska oil fields, may be contributing 30%–50%, on average, to observed BC at Utqiaġvik/Barrow in January and February 2014, with the remainder from outside the region. These findings highlight the importance of local Arctic emissions, and the need for improved emission inventories in the Arctic.

Plain Language Summary. Black carbon (BC), emitted by incomplete combustion of biomass or fossil fuels, is a short-lived climate forcer contributing to global and Arctic climate warming. BC and other aerosols are transported from emission regions in midlatitudes into the Arctic during winter and spring, a phenomenon called Arctic haze. However, there are local sources of BC within the Arctic, such as wood burning for residential heating, gas flaring during oil and gas extraction or power generation, contributing to BC concentrations in the Arctic. In this work, a detailed meteorological and chemical transport model is used to simulate Arctic BC during wintertime. In particular, the influence of processes removing BC from the atmosphere (precipitation and dry deposition) is examined. The model sensitivity to these processes varies across the Arctic, and explains some of the differences with observed BC at Arctic sites. Runs over northern Alaska show an important contribution from local and regional emissions to observed BC, notably from North Slope of Alaska petroleum extraction emissions. The findings from this study highlight the need for improved anthropogenic emissions over the Arctic, as well as important sensitivities to modeled removal processes.