In remote marine areas, biogenic productivity and atmospheric particulate are coupled through dimethylsulfide (DMS) emission by phytoplankton. Once in the atmosphere, the gaseous DMS is oxidized to produce H 2 SO 4 and methanesulfonic acid (MSA); both species can affect the formation of cloud condensation nuclei. This study analyses eight years of biogenic aerosol evolution and variability at two Arctic sites: Thule (76.5 • N, 68.8 • W) and Ny Ålesund (78.9 • N, 11.9 • E). Sea ice plays a key role in determining the MSA concentration in polar regions. At the beginning of the melting season, in April, up to June, the biogenic aerosol concentration appears inversely correlated with sea ice extent and area, and positively correlated with the extent of the ice-free area in the marginal ice zone (IF-MIZ). The upper ocean stratification induced by sea ice melting might have a role in these correlations, since the springtime formation of this surface layer regulates the accumulation of phytoplankton and nutrients, allowing the DMS to escape from the sea to the atmosphere. The multiyear analysis reveals a progressive decrease in MSA concentration in May at Thule and an increase in July August at Ny Ålesund. Therefore, while the MSA seasonal evolution is mainly related with the sea ice retreat in April, May, and June, the IF-MIZ extent appears as the main factor affecting the longer-term behavior of MSA.2 of 12 stronger cooling through direct radiative forcing. Conversely, the contributions to cloud condensation nuclei precursors from MSA and from DMS-derived sulfate/sulfuric acid are comparable, leading to similar changes in the aerosol indirect effect [3].While nonsea salt (nss) SO 4 2− has many sources in addition to biogenic activity (e.g., volcanic and anthropic), MSA is uniquely due to biogenic sources. For this reason, MSA concentration records in ice cores were used to investigate past climate through marine primary production which, in turn, is related to sea ice and other environmental parameters [4,5]. Indeed, the MSA atmospheric concentration is regulated by multiple processes that can be summarized into two main categories: (i) biotic factors such as primary productivity and phytoplankton species and (ii) abiotic factors that include air and sea temperatures, marine mixing layer depth, wind speed, sea-air exchange, atmospheric concentration of oxidants (O 3 , OH, and BrO), gas phase versus aqueous phase oxidation pathways, radiation, and, in polar regions, sea ice. The Arctic plays an important role in the global climate system. The Arctic is warming at a rate almost two times larger than the global average rate (Serreze et al., [6] and references therein). At the same time, the Arctic sea ice area has decreased at a rate of 2.7% per decade [7]. These factors are expected to influence the primary production and biogenic compounds sea-air exchange in the Arctic Ocean [8].Recent studies (e.g., Boyce et al., [9]) suggest that global marine primary production has been declining during the last century and is expe...
