Particle-Size Distributions and Solubility of Aerosol Iron Over the Antarctic Peninsula During Austral Summer

This study provides new data on the properties of aerosol iron (Fe) over the Antarctic Peninsula, one of the fastest warming regions on Earth in recent decades. Atmospheric deposition delivers Fe, a limiting micronutrient, to the Southern Ocean, and aerosol particle size influences the air-to-sea deposition rate and fractional solubility of aerosol Fe. Size-segregated aerosols were collected at Palmer Station on the West Antarctic Peninsula during austral summer 2016–2017. Results show single-mode size distribution of aerosol Fe, peaking at 4.4 μm diameter. The average concentration of total aerosol Fe was 1.3 (±0.40) ng m⁻³ (range 0.74–1.8 ng m⁻³). High concentrations of total aerosol Fe occurred in January, implying increased Fe source strength then. Total labile Fe varied between 0.019 and 0.095 ng m⁻³, and labile Fe (II) accounted for ~90% of the total labile Fe. The average fractional solubility for total Fe was 3.8% (±1.5%) (range 2.5–7.3%). Estimated dry deposition fluxes for the study period were 3.2 μg m⁻² year⁻¹ for total labile Fe and 83 μg m⁻² year⁻¹ for total Fe in aerosols. We speculate that local and regional dust sources in Antarctica contributed to the observed aerosol Fe in austral summer and that warming on the Antarctic Peninsula during the past half century may have increased the formation of dust sources in this region. The potential biogeochemical impact of atmospheric Fe input to the West Antarctic Peninsula shelf waters and adjacent pelagic surface waters of the Southern Ocean may need to be re-evaluated.