Identification of Necessary Conditions for Arctic Transport of Smoke from United States Fires

The deposition of black carbon (BC), a dark absorbing aerosol, is a significant contributor to observed warming trends in the Arctic (Hansen and Nazarenko, 2004; Jacobson et al., 2007). Biomass burning outside of the Arctic, including wildland prescribed fires, is a major potential source of Arctic BC. Therefore, limiting or eliminating spring prescribed burning has been suggested to Congress as a BC reduction technique (e.g., Zender, 2007). However, there are large uncertainties in the current estimates of the sources, source regions, and transport and transformation pathways of BC transported to the Arctic region (Shindell et al., 2008; Hegg et al., 2009, Quinn et al., 2008). This study is the first comprehensive examination of the meteorological conditions required for emissions from the contiguous United States (CONUS) to be transported to Arctic. Using a simple trajectory modeling technique, we characterize the potential for transport of emissions from fires in CONUS to reach the Arctic and Greenland. The potential for Arctic transport is examined as • A 30-year climatology (1980-2009) of transport potential based on trajectory modeling using historical meteorology and split out by season, month, starting plume injection height, and time to reach the Arctic. • A real-time (daily) forecast system of transport potential to the Arctic that shows which layers of the atmosphere can reach the Arctic today, tomorrow, and the next day. The methods used here do not include wet or dry deposition and other factors that can further limit the ability of actual emissions to reach and deposit in the Arctic. Instead, by focusing on only one necessary aspect (a necessary but not sufficient condition) – the ability of the atmosphere to transport emissions – this study examines • Under what meteorological transport conditions can CONUS emissions potentially impact the Arctic? However, this allows for the ability to answer the corollary question: • Under what meteorological transport conditions will CONUS emissions not impact the Arctic? This inverse question allows for identification of times, locations, and plume injection heights where emissions sources (such as a prescribed burn) will not have an impact on the Arctic. This knowledge allows for both more targeted future studies and more precise mitigation strategies that do not focus on areas and times where Arctic impact is unlikely