Activity 1: Carbonaceous Aerosol and Climate
It is widely recognized that black carbon (BC) aerosol directly warms the atmosphere, especially in snow-covered regions where the high surface albedo accentuates its effects. Unlike other climate warming agents such as the long-lived greenhouse gases, the radiative effects of BC on the atmosphere are short-lived, determined by its multi-day lifetime for deposition to the surface. Given the large uncertainties in models simulating the dynamic radiative effects of BC [Koch et al., 2009], there is considerable interest in better identifying sources, atmospheric loadings, and loss processes for such light-absorbing aerosols. Indeed, measurements of the size distribution of BC aerosol are highly limited. Major sources are industry and BB, either through wildfires or biofuels. Anthropogenic versus natural input is difficult to assess, given the increasing prevalence of forest fires arising through regional warming, forest management processes and forest die-off (such as that associated with the pine bark beetle infestation in British Columbia). Whereas there have been many measurements of BC in heavily populated regions, there is a notable paucity of data from remote environments. This issue is of particular importance in snow-covered regions where BC deposition can affect the albedo of the snowpack and regional radiative forcing [McConnell et al., 2007].
Key questions to be addressed:
- How do BC and OC loadings from biomass burning compare with anthropogenic BC and OC over the Arctic and Western Canada?
- What is the relative importance of the mechanisms for BC and OC deposition to Arctic snow and ice? In particular, what is the vertical distribution of BC in the Arctic atmosphere? Is there evidence for dry deposition in the boundary layer and/or via ice clouds?
- What are the levels and sources of BC and OC, including brown carbon, in snow? What are the implications of carbonaceous loadings in snow on radiative forcing?
- What will be the consequences of reducing or eliminating BC?