Black carbon in the Arctic: The underestimated role of gas flaring and residential combustion emissions
Arctic haze is a seasonal phenomenon with high trations of BC due to residential combustion emissions are concentrations of accumulation-mode aerosols occurring in 150% higher when using daily emissions than when using the Arctic in winter and early spring. Chemistry transport annually constant emissions. While there are concentration Geoscientific models and climate chemistry models struggle to reproduce reductions in summer, they are smaller than the winter in- Instrumentation this phenomenon, and this has recently prompted changes in creases, leading to a systematic increase of annual mean Arc- Methods and aerosol removal schemes to remedy the modeling problems. tic BC surface concentrations due to residential combustion Open Access In this paper, we show that shortcomings in current emis- by 68% when using daily emissions. A large part (93%) Data Systems sion data sets are at least as important. We perform a 3 yr of this systematic increase can be captured also when us- model simulation of black carbon (BC) with the Lagrangian ing monthly emissions; the increase is compensated by a de- particle dispersion model FLEXPART. The model is driven creased BC burden at lower latitudes. In a comparison with Geoscientific with a new emission data set (“ECLIPSE emissions”) which BC measurements at six Arctic stations, we find that us- Model Development includes emissions from gas flaring. While gas flaring is es- ing daily-varying residential combustion emissions and in- Open Access timated to contribute less than 3%of global BC emissions in troducing gas flaring emissions leads to large improvements this data set, flaring dominates the estimated BC emissions of the simulated Arctic BC, both in terms of mean concentra- in the Arctic (north of 66◦ N). Putting these emissions into tion levels and simulated seasonality. Case studies based on Hydrology and our model, we find that flaring contributes 42%to the annual BC and carbon monoxide (CO) measurements from the Zep- Earth System mean BC surface concentrations in the Arctic. In March, flar- pelin observatory appear to confirm flaring as an important ing even accounts for 52%of all Arctic BC near the surface. BC source that can produce pollution plumes in the Arctic Sciences Open Access Most of the flaring BC remains close to the surface in the with a high BC/CO enhancement ratio, as expected for this Arctic, so that the flaring contribution to BC in the middle source type. BC measurements taken during a research ship and upper troposphere is small. Another important factor de- cruise in the White, Barents and Kara seas north of the re- termining simulated BC concentrations is the seasonal varia- gion with strong flaring emissions reveal very high concen- Ocean Science tion of BC emissions from residential combustion (often also trations of the order of 200–400 ngm−3. The model under- called domestic combustion, which is used synonymously in estimates these concentrations substantially, which indicates Open Access this paper).We have calculated daily residential combustion that the flaring emissions (and probably also other emissions emissions using the heating degree day (HDD) concept based in northern Siberia) are rather under- than overestimated in on ambient air temperature and compare results from model our emission data set. Our results suggest that it may not be simulations using emissions with daily, monthly and annual “vertical transport that is too strong or scavenging rates that Solid Earth time resolution. In January, the Arctic-mean surface concen- are too low” and “opposite biases in these processes” in the Arctic and elsewhere in current aerosol models, as suggested in a recent review article (Bond et al., Bounding the role of black carbon in the climate system: a scientific assessment, J. Geophys. Res., 2013), but missing emission sources and lacking time resolution of the emission data that are causing opposite model biases in simulated BC concentrations in the Arctic and in the mid-latitudes.