Pan-Arctic seasonal cycles and long-term trends of aerosol properties from ten observatories

• Main Authors: Schmale, Julia, Sharma, Sangeeta, Decesari, Stefano, Pernov, Jakob, Massling, Andreas, Hansson, Hans-Christen, Von Salzen, Knut, Skov, Henrik, Andrews, Betsy, Quinn, Trish, Upchurch, Lucia, Eleftheriadis, Kostas, Traversi, Rita
• Format: Text
• Language: unknown
• Published: 2022
• Subjects: Arctic; Kendall; Kevo; Tiksi; albedo; black carbon
• Online Access: https://doi.org/10.5194/acp-2021-756; https://infoscience.epfl.ch/record/292216/files/acp-2021-756%20%281%29.pdf; http://infoscience.epfl.ch/record/292216

Even though the Arctic is remote, aerosol properties observed there are strongly influenced by anthropogenic emissions from outside the Arctic. This is particularly true for the so-called Arctic haze season (January through April). In summer (June through September), when atmospheric transport patterns change, and precipitation is more frequent, local Arctic, i.e. natural sources of aerosols and precursors, play an important role. Over the last decades, significant reductions in anthropogenic emissions have taken place. At the same time a large body of literature shows evidence that the Arctic is undergoing fundamental environmental changes due to climate forcing, leading to enhanced emissions by natural processes that may impact aerosol properties. In this study, we analyze nine aerosol chemical species and four particle optical properties from ten Arctic observatories (Alert, Gruvebadet, Kevo, Pallas, Summit, Thule, Tiksi, Barrow, Villum, Zeppelin) to understand changes in anthropogenic and natural aerosol contributions. Variables include equivalent black carbon, particulate sulfate, nitrate, ammonium, methanesulfonic acid, sodium, iron, calcium and potassium, as well as scattering and absorption coefficients, single scattering albedo and scattering Ångström exponent. First, annual cycles are investigated, which despite anthropogenic emission reductions still show the Arctic haze phenomenon. Second, long-term trends are studied using the Mann-Kendall Theil-Sen slope method. We find in total 28 significant trends over full station records, i.e. spanning more than a decade, compared to 17 significant decadal trends. The majority of significantly declining trends is from anthropogenic tracers and occurred during the haze period, driven by emission changes between 1990 and 2000. For the summer period, no uniform picture of trends has emerged. Twenty-one percent of trends, i.e. eleven out of 57, are significant, and of those five are positive and six are negative. Negative trends include not only anthropogenic ...