Atmospheric Deposition of Local Mineral Dust Delivers Phosphorus to the Greenland Ice Sheet

Aerosol composition, size, and deposition rate determine the impact these particles have on cryosphere environments. Mineralogical, biological, and geochemical characteristics of aerosols collected over two years from the southwest Greenland Ice Sheet indicate that aerosols delivered via dry deposition and in snow primarily consisted of silicate minerals, with mean particle diameters of 1.01 ± 1.58 μm (2016) and 0.76 ± 0.87 μm (2017) for dry deposition and 2.4 ± 3.2 μm for dust delivered in snow (2017). The rare earth element signature of the delivered dust was typical of nearby Greenlandic lithologies, and combining this with other geochemical results and airmass history modeling indicated that the airborne mineral dust collected on-ice was likely from local emission sources, namely nearby proglacial plains. Dust and snow deposition rates were used to estimate phosphorus delivery to the ice surface at a rate of 1.2 mg·m^-2·year^-1, which could fuel estimated pigmented glacier ice algal cell abundances of 8.6 × 10³ cells·mL^-1, a value consistent with glacier ice algal bloom cell densities documented in the region. The eukaryotic communities in air and snow samples were dominated by algae and fungi, respectively, with both sample types also hosting various bacteria. These results suggest that the airborne transfer of glacier ice and snow algae may be a method by which fresh cryosphere surfaces become inoculated with these pigmented organisms. Collectively, these findings highlight the biogeochemical links between aerosols and the ice sheet surface, which have impacts on glacier ice algal growth and the corresponding surface ice albedo and melting.