Is cloud seeding in coastal Antarctica linked to bromine and nitrate variability in snow?

Abstract

Considering the significance of methanesulfonate (MSA) in the sulfur cycle and global climate, we analyzed MSA and other ionic species in snow from the coastal Larsemann Hills, East Antarctica. MSA concentrations recorded were high (0.58 ± 0.7 µM) with ice-cap regions showing significantly higher concentrations (df = 10, p < 0.001) than ice-free regions. High nutrient concentration in ice-cap snow appears to have favored algal growth (7.6 × 102 cells l − 1) with subsequent production of brominated compounds. The consequent elevated Br − (3.2 ± 2.2 µM) in the ice-cap region could result in the release of Br atoms through photoactivated reactions on aerosols and the snow surface. Activated Br atoms in the atmosphere could react with ozone leading to BrO enhancement with subsequent dimethylsulfide (DMS) oxidation and production of sulfur aerosols. Since BrO based DMS oxidation is much faster than the OH/NO3 pathway, elevated Br − in ice-cap snow could contribute more than ice-free sites towards formation of cloud condensation nuclei at the expense of ozone.