Pan-Arctic seasonal cycles and long-term trends of aerosol properties from 10 observatories
Pan-Arctic seasonal cycles and long-term trends of aerosol properties from 10 observatories
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DOI：
10.5194/acp-22-3067-2022
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发表时间：
2022-03
影响因子：
6.3
通讯作者：
J. Schmale;Sangeeta Sharma;S. Decesari;J. Pernov;A. Massling;H. Hansson;K. von Salzen;H. Skov;E. Andrews;P. Quinn;L. Upchurch;K. Eleftheriadis;R. Traversi;S. Gilardoni;M. Mazzola;J. Laing;P. Hopke
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文献类型：
--
作者：
J. Schmale;Sangeeta Sharma;S. Decesari;J. Pernov;A. Massling;H. Hansson;K. von Salzen;H. Skov;E. Andrews;P. Quinn;L. Upchurch;K. Eleftheriadis;R. Traversi;S. Gilardoni;M. Mazzola;J. Laing;P. Hopke
抽象的。尽管北极地处偏远，但那里观测到的气溶胶特性受到北极以外的人为排放的强烈影响。在所谓的北极雾霾季节(1月至4月)尤其如此。在夏季(6月至9月)，当大气传输模式发生变化，降水更加频繁时，北极的当地来源，即气溶胶和前体的自然来源，发挥着重要作用。在过去的几十年里，人为排放已经显著减少。与此同时，大量文献表明，由于气候强迫，北极正在经历根本性的环境变化，导致自然过程排放增加，可能影响气溶胶特性。在这项研究中，我们分析了来自10个北极观测站(Alert、Kavo、Pallas、Summit、Thule、Tiksi、Barrow/UtqiaġVik、Villum以及Gruvebadet和Zeppelin观测站--均位于NY-älesund研究站)的9种气溶胶化学物质和4种粒子的光学性质，以了解人为和自然气溶胶贡献的变化。变量包括当量黑碳、颗粒硫酸盐、硝酸盐、铵、甲烷磺酸、钠、铁、钙和钾，以及散射和吸收系数、单次散射反照率和散射安斯特伦指数。首先，研究了年周期，尽管人类活动减少了排放，但仍显示出北极雾霾现象。其次，使用Mann-Kendall Theil-Sen斜率方法研究了长期趋势。我们发现全站记录共有41个显著趋势，即跨越十多年，相比之下，有26个显著的年代际趋势。大多数显著下降的趋势来自人为示踪剂，发生在雾霾期间，原因是1990至2000年间排放量的变化。在夏季期间，还没有出现统一的趋势图景。26%的趋势，即73个趋势中的19个是重要的，其中5个是积极的，14个是负面的。负面趋势不仅包括凯沃的等量黑碳等人为示踪剂，也包括Alert的甲烷磺酸和非海盐钙等自然指示剂。在Gruvebadet观察到硫酸盐的积极趋势。目前还没有观察到自然气溶胶贡献发生重大变化的明显证据。然而，通过测试Mann-Kendall Theil-Sen方法的灵敏度，我们发现气溶胶属性中−1的单调变化需要在十年内检测到显著的趋势。这突显出，需要远远超过十年的长期努力才能捕捉到较小的变化。特别重要的是要了解北极正在发生的自然变化，那里的年际变化可能很大，例如森林火灾排放及其对气溶胶种群的影响。为了调查气候变化对气溶胶种群的影响和由此产生的气候反馈，需要对更特定于自然来源的示踪剂以及颗粒微观物理特性进行长期观察，如粒度分布，这些特性可用于确定颗粒种群的变化，这些变化不是以质量为导向的方法，如散装化学成分。
Abstract. 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 sources, i.e., natural sources of aerosols and precursors, play an important role. Over the last few 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 9 aerosol chemical species and 4 particle optical properties from 10 Arctic observatories (Alert, Kevo, Pallas, Summit, Thule, Tiksi, Barrow/Utqiaġvik, Villum, and Gruvebadet and Zeppelin Observatory – both at Ny-Ålesund Research Station) 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 41 significant trends over full station records, i.e., spanning more than a decade, compared to 26 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-six percent of trends, i.e., 19 out of 73, are significant, and of those 5 are positive and 14 are negative. Negative trends include not only anthropogenic tracers such as equivalent black carbon at Kevo, but also natural indicators such as methanesulfonic acid and non-sea-salt calcium at Alert. Positive trends are observed for sulfate at Gruvebadet. No clear evidence of a significant change in the natural aerosol contribution can be observed yet. However, testing the sensitivity of the Mann–Kendall Theil–Sen method, we find that monotonic changes of around 5 % yr−1 in an aerosol property are needed to detect a significant trend within one decade. This highlights that long-term efforts well beyond a decade are needed to capture smaller changes. It is particularly important to understand the ongoing natural changes in the Arctic, where interannual variability can be high, such as with forest fire emissions and their influence on the aerosol population. To investigate the climate-change-induced influence on the aerosol population and the resulting climate feedback, long-term observations of tracers more specific to natural sources are needed, as well as of particle microphysical properties such as size distributions, which can be used to identify changes in particle populations which are not well captured by mass-oriented methods such as bulk chemical composition.