Spatial Distributions of Black Carbon and Mineral Dust in Air and Snow Surface Layers upon Svalbard Glaciers

Black carbon (BC) and mineral dust (MD) when deposited on snow and glaciers can have strong effects on the radiative balance of the Arctic. The reflectivity of snow surface (albedo), a dominant parameter affecting the energy balance in Polar Regions, depends on the snow grain size, wetness and impurities in the near-surface snow layer (Meinander et al., 2014). Estimation of snow albedo is important for predicting seasonal snow developments (e.g. Sauter and Obleitner 2015), for determining glacier mass budgets (van Pelt and Kohler 2015) and for calculating the regional and global energy budgets (Wittmann et al, 2017). This topic has attracted strong attention recently (Groot Zwaaftink et al. 2017; Wittmann et al, 2017; Winiger et al. 2017) and it was discussed as a major issue at the recent Svalbard Science Conference (SSC) in Oslo Nov. 2017. Part of the concern is due to the fact that about 50% of BC sources impacting Arctic are located in North Europe and Russia (Popovicheva et al, 2017) and MD sources (e.g. due to volcanic eruptions or lifting by wind) are also often located in northern high latitudes (Groot Zwaaftinket al, 2016). The influence of the latter is still underestimated and actually expected to increase due to the enlargement of deglaciated areas in the Northern hemisphere. A current significant open issue on this topic is the relative impact of MD with respect to BC when they are deposited on the snow surface: for example Icelandic volcanic dust is darker and more absorbing than MD from most other regions and its total absorption in snow is somewhat similar to BC (Wittmann et al, 2017). A second main issue is the spatial variability of MD and BC on the snow surface, even at the scale of a single glacier. These uncertainties in the deposition processes and spatial distribution over Arctic glaciers require more systematic and combined snow-atmospheric studies. Last but not the least, BC and MD transports and deposition in Arctic may be important in winter months (or very early spring), for which much less observations are available, and may successively impact on snow properties in spring and summer during melt.