Abstract
Short-lived aerosols and pollutants transported from northern mid-latitudes have amplified the short term warming in the Arctic region. Among those black carbon is recognized as the second most important human emission in regards to climate forcing, behind carbon dioxide, with a total climate forcing of +1.1Wm-2. Studies have suggested that cropland burning may be a large contributor to the black carbon emissions which are directly deposited on the snow in the Arctic. However, commonly applied atmospheric transport models rely on estimates of black carbon emissions from cropland burning which are known to be highly inaccurate in both the amount and the timing of release. Instead, this study quantifies the potential for the deposition of hypothetical black carbon emissions from known cropland burning in Russia, identified by the Moderate Resolution Imaging Spectroradiometer (MODIS) active fire detections, through low-level transport to the snow in the Arctic using wind vectors from the European Centre for Medium-Range Weather Forecasts’ ERA-Interim Reanalysis product. Our results confirm that Russian cropland burning is a potentially significant source of black carbon deposition on the Arctic snow in the spring despite the low injection heights associated with cropland burning. Approximately 10% of the observed spring (March - May) cropland active fires (7% annual) likely contribute to black carbon deposition on the Arctic snow from as far south as at least 40°N. Furthermore, our results show that potential spring black carbon emissions from cropland burning in Russia can be deposited beyond 80°N, however, the majority (~90% - depending on injection height) of all potential spring deposition occurs below 75°N.
Highlights
Over the past 30 years, the Arctic surface air temperature has risen at rates more than double of those anywhere else on Earth (NOAA, 2017)
On average between 2003 and 2015, approximately 4–10% of the March, April, and May observed fire occurrences are within regions with successful transport to the Arctic. These results represent a unique quantification of the fraction of observed burning within Russian croplands which are potentially able to contribute to the deposition of black carbon (BC) on the Arctic snow
This study introduces a simple approach to assess the potential for BC deposition in the Arctic based on reanalysis data of observed meteorological conditions and confirmed cropland burning
Summary
Over the past 30 years, the Arctic surface air temperature has risen at rates more than double of those anywhere else on Earth (NOAA, 2017) This has resulted in the drastic loss of sea ice, increased release of stored carbon and methane from melting permafrost, and substantial impacts on migratory patterns of birds and animals among many other environmental changes (EPA, 2016; NOAA, 2017; NSIDC, 20171). While the reported increases in annual and especially cold-season temperatures (NOAA, 2017) are large enough to directly result in the loss of surface snow and sea ice, atmospheric pollutants—and especially black carbon (BC) deposition on the snow and ice surface—have contributed to the changes in snow/ice albedo and the subsequent accelerated rate of melting (Ramanathan and Carmichael, 2008; Dou and Xiao, 2016). A new international initiative PACES (air Pollution in the Arctic: Climate Environment and Societies) under the partnership of the International Global Atmospheric Chemistry Project and the International Arctic Science Committee emphasizes the importance of studying processes controlling Arctic air pollution with a focus on accurately identifying the potential BC source locations and the relative contributions to the potential deposition on the Arctic snow (Arnold et al, 2016)
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