Methane transport from the active layer to lakes in the Arctic using Toolik Lake, Alaska, as a case study
Methane transport from the active layer to lakes in the Arctic using Toolik Lake, Alaska, as a case study
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DOI：
10.1073/pnas.1417392112
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发表时间：
2015-03
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影响因子：
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通讯作者：
A. Paytan;A. Lecher;N. Dimova;K. Sparrow;F. G. Kodovska;Joseph Murray;S. Tulaczyk;J. Kessler
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文献类型：
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作者：
A. Paytan;A. Lecher;N. Dimova;K. Sparrow;F. G. Kodovska;Joseph Murray;S. Tulaczyk;J. Kessler
重要意义甲烷，一种温室气体，导致全球变暖。我们发现，来自北极季节性融化活跃层的富含甲烷的水流入阿拉斯加的图利克湖。这可能是北极湖泊中甲烷运输和排放的一个以前未被认识到的重要管道。活跃层对甲烷输入的控制与影响湖泊甲烷产生的控制是根本不同的，这些过程对气候和环境变化的响应也是截然不同的。对甲烷排放量的预测的准确性以及最终北极气候变化的预期程度，取决于对该区域甲烷动态的更好了解，包括对活动层内甲烷生产和运输过程的控制。北极的甲烷排放很重要，可能会导致全球变暖。虽然北极湖泊的甲烷排放量有很好的记录，但需要采用各种方法来量化活跃层地下水对整个湖泊甲烷收支的相对贡献。在这里，我们报道了阿拉斯加Toolik湖土壤/地下水、氡和镭的天然示踪剂以及甲烷浓度的测量，以评估活跃层水作为湖泊甲烷的外源来源所起的作用。活动层甲烷、镭和氡的平均浓度均高于湖水(分别为1.6x104nM、61.6dpm⋅m−3和4.5x105dpm⋅m−3，而湖水分别为1.3×102nM、5.7dpm⋅m−3和4.4×103dpm⋅m−3)。从活跃层到托利克湖的甲烷运移基于地球化学示踪氡(高达2.9g⋅m−2⋅y−1)可以占该湖甲烷排放的很大一部分。湖水中氡活度和甲烷浓度(R2>；0.69)之间强烈的但在空间和时间上可变的相关性表明，控制甲烷从活跃层排放的参数也不同。北极变暖可能会扩大活动层，增加排放，从而增加向湖泊和从湖泊到大气的甲烷通量，加剧全球变暖。还需要做更多的工作来量化和阐明控制活动层甲烷通量的过程，以预测这种通量未来可能如何变化，并评估活动层与水有关的甲烷输入对区域和全球的贡献。
Significance Methane, a greenhouse gas, contributes to global warming. We show that methane-rich water from the seasonally thawed active layer in the Arctic flows into Toolik Lake, Alaska. This may be an important previously unrecognized conduit for methane transport and emissions in Arctic lakes. The controls on methane input from the active layer are fundamentally different than those affecting methane production within lakes, and the response of these processes to climate and environmental change is also distinct. The accuracy of predictions of methane emissions and ultimately the extent of climate change that can be expected in the Arctic depend on a better understanding of methane dynamics in the region, including the controls over methane production and transport processes within the active layer. Methane emissions in the Arctic are important, and may be contributing to global warming. While methane emission rates from Arctic lakes are well documented, methods are needed to quantify the relative contribution of active layer groundwater to the overall lake methane budget. Here we report measurements of natural tracers of soil/groundwater, radon, and radium, along with methane concentration in Toolik Lake, Alaska, to evaluate the role active layer water plays as an exogenous source for lake methane. Average concentrations of methane, radium, and radon were all elevated in the active layer compared with lake water (1.6 × 104 nM, 61.6 dpm⋅m−3, and 4.5 × 105 dpm⋅m−3 compared with 1.3 × 102 nM, 5.7 dpm⋅m−3, and 4.4 × 103 dpm⋅m−3, respectively). Methane transport from the active layer to Toolik Lake based on the geochemical tracer radon (up to 2.9 g⋅m−2⋅y−1) can account for a large fraction of methane emissions from this lake. Strong but spatially and temporally variable correlations between radon activity and methane concentrations (r2 > 0.69) in lake water suggest that the parameters that control methane discharge from the active layer also vary. Warming in the Arctic may expand the active layer and increase the discharge, thereby increasing the methane flux to lakes and from lakes to the atmosphere, exacerbating global warming. More work is needed to quantify and elucidate the processes that control methane fluxes from the active layer to predict how this flux might change in the future and to evaluate the regional and global contribution of active layer water associated methane inputs.