Antarctic Aerosols and Climate

Aerosols exert direct and indirect impacts on the climate via their interaction with the incoming solar radiation and participation in cloud microphysics. These aerosol effects, to a large extent, depend on the size range of these particles. The remote oceanic regions and Antarctica serve as background sites to assess the climatic impacts of aerosols. This study presents a review of literature on the Antarctic aerosol measurements and their climatic effects. Also reported are the measurements of aerosol concentrations and number size distributions made at a coastal Antarctic station, Maitri, during January–February 2005. Some ship-based measurements of aerosols from coastal Antarctic waters near the ice-shelf region are also reported. The high-resolution aerosol size distributions were measured over a wide size range of 3 nm–20 µm. The variations in number size distributions in Aitken, accumulation, and coarse mode particles are discussed. At the Maitri station, the total concentrations of coarse particles (0.5–20 µm diameter) remained below 1.0 cm⁻³, with an accumulation mode between 0.72 and 0.77 µm in diameter. However, these particles were found to be in the range of 2–40 cm⁻³ near the ice-shelf region at Antarctic coastal waters. The total concentration of submicrometer (0.003–0.7 µm) particles varied in the range of 100–800 particles cm⁻³ in January and between 100 and 2000 particles cm⁻³ in February at Maitri. Significant variability was found in the magnitude and size range of different modes in the Aitken mode at the Maitri and ice-shelf region. The total concentration of particles over the coastal Antarctic waters near the ice shelf was up to two orders of magnitude higher than that of the Maitri station. This high concentration of ultrafine particles in the coastal Antarctic environment could be attributed to the gas-to-particle conversion in the sub-polar oceanic region around Antarctica. The cyclonic storms revolving around the Antarctic continent enhanced the aerosol number concentration at the Maitri station. The observed size distributions of aerosols at Maitri and ice-shelf locations are discussed in their generation, transformation, and climatic impacts.