Scripps Institution of Oceanography, University of California at San Diego, La Jolla, CA 92093, USA.
Department of Environmental Research and Monitoring, Swedish Museum of Natural History, Stockholm, Sweden.
Sci Total Environ. 2022 Aug 25;836:155477. doi: 10.1016/j.scitotenv.2022.155477. Epub 2022 Apr 23.
Arctic mercury (Hg) concentrations respond to changes in anthropogenic Hg emissions and environmental change. This manuscript, prepared for the 2021 Arctic Monitoring and Assessment Programme Mercury Assessment, explores the response of Arctic Ocean Hg concentrations to changing primary Hg emissions and to changing sea-ice cover, river inputs, and net primary production. To do this, we conduct a model analysis using a 2015 Hg inventory and future anthropogenic Hg emission scenarios. We model future atmospheric Hg deposition to the surface ocean as a flux to the surface water or sea ice using three scenarios: No Action, New Policy (NP), and Maximum Feasible Reduction (MFR). We then force a five-compartment box model of Hg cycling in the Arctic Ocean with these scenarios and literature-derived climate variables to simulate environmental change. No Action results in a 51% higher Hg deposition rate by 2050 while increasing Hg concentrations in the surface water by 22% and <9% at depth. Both "action" scenarios (NP and MFR), implemented in 2020 or 2035, result in lower Hg deposition ranging from 7% (NP delayed to 2035) to 30% (MFR implemented in 2020) by 2050. Under this last scenario, ocean Hg concentrations decline by 14% in the surface and 4% at depth. We find that the sea-ice cover decline exerts the strongest Hg reducing forcing on the Arctic Ocean while increasing river discharge increases Hg concentrations. When modified together the climate scenarios result in a ≤5% Hg decline by 2050 in the Arctic Ocean. Thus, we show that the magnitude of emissions-induced future changes in the Arctic Ocean is likely to be substantial compared to climate-induced effects. Furthermore, this study underscores the need for prompt and ambitious action for changing Hg concentrations in the Arctic, since delaying less ambitious reduction measures-like NP-until 2035 may become offset by Hg accumulated from pre-2035 emissions.
北极汞（Hg）浓度对人为 Hg 排放和环境变化的变化做出响应。本报告为 2021 年北极监测与评估方案汞评估编写，探讨了北极海洋 Hg 浓度对不断变化的主要 Hg 排放以及不断变化的海冰覆盖、河流输入和净初级生产力的响应。为此，我们使用 2015 年 Hg 清单和未来人为 Hg 排放情景进行了模型分析。我们将未来大气 Hg 沉积到海洋表面的通量模拟为海水或海冰中的通量，使用三种情景：不采取行动、新政策（NP）和最大可行减排（MFR）。然后，我们使用这些情景和文献中得出的气候变量来驱动北极海洋五组分 Hg 循环箱模型，以模拟环境变化。不采取行动情景导致到 2050 年 Hg 沉积率增加 51%，同时将表层水 Hg 浓度增加 22%，<9%在深处。实施时间分别为 2020 年和 2035 年的两种“行动”情景（NP 和 MFR）到 2050 年将导致 Hg 沉积率降低 7%（NP 推迟到 2035 年）至 30%（2020 年实施 MFR）。在最后一种情景下，海洋 Hg 浓度在表面下降 14%，在深处下降 4%。我们发现，海冰覆盖的减少对北极海洋产生了最强的 Hg 还原胁迫，而增加河流流量则增加了 Hg 浓度。当气候情景结合起来时，到 2050 年，北极海洋的 Hg 浓度将下降≤5%。因此，我们表明，与气候引起的影响相比，排放引起的未来北极海洋变化的幅度可能很大。此外，这项研究强调了需要采取迅速和雄心勃勃的行动来改变北极的 Hg 浓度，因为将不那么雄心勃勃的减排措施（如 NP）推迟到 2035 年可能会被 2035 年前排放的 Hg 所抵消。
