Interannual, summer, and diel variability of CH 4 and CO 2 effluxes from Toolik Lake, Alaska, during the ice-free periods 2010–2015
Interannual, summer, and diel variability of CH 4 and CO 2 effluxes from Toolik Lake, Alaska, during the ice-free periods 2010–2015
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2010 年至 2015 年无冰期阿拉斯加 Toolik 湖 CH 4 和 CO 2 流出量的年际、夏季和昼夜变化
DOI：
10.1039/d0em00125b
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发表时间：
2020
期刊：
影响因子：
--
通讯作者：
Kling, George W.
中科院分区：
文献类型：
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作者：
Eugster, Werner;DelSontro, Tonya;Shaver, Gaius R.;Kling, George W.
北极加速变暖导致人们对北极水体潜在碳排放量的担忧。然而，水生二氧化碳（CO2）和甲烷（CH 4）通量的测量仍然很少，特别是在高分辨率和长时间。利用直接涡度相关通量（EC）技术首次对阿拉斯加北方的深冰湖图里克湖（Toolik Lake）在6个无冰期（2010-2015年）的甲烷（CH 4）和二氧化碳（CO2）排放进行了测量。该湖的二氧化碳通量估计值（日均排放量为16.7 ± 5.3 mmol m-2 d-1）与1975-1989年使用不同方法的早期估计值非常一致。2010-2015年的CH 4排放量（平均为0.13 ± 0.06 mmol m−2 d−1）显示出的年际变化是平均昼夜变化的4.1倍，但平均通量几乎比1990年和2011-2012年从单一水样获得的早期估计低一个数量级。因此，图里克湖的总体全球变暖潜势（GWP）主要由CO2排放控制，占无冰期GWP 26-90 g CO2，eq m−2的86-93%。昼夜变化的通量也很重要，高达2倍（CH 4）至4倍（CO2）之间的差异最高夜间和最低白天流出。在夏季无冰期间，平均而言，CH 4通量增加2倍，在上半年的夏天，然后保持几乎恒定，而CO2排放量几乎保持不变，在整个夏天，结束与线性增加在最后1-2周的测量。由于这个26米深的湖泊底部温度较低，并且没有沸腾和间歇性通量事件，图里克湖和其他深冰川湖可能不是温室气体排放的热点，但它们仍然对北极的整体全球升温潜能值做出了贡献。
Accelerated warming in the Arctic has led to concern regarding the amount of carbon emission potential from Arctic water bodies. Yet, aquatic carbon dioxide (CO2) and methane (CH4) flux measurements remain scarce, particularly at high resolution and over long periods of time. Effluxes of methane (CH4) and carbon dioxide (CO2) from Toolik Lake, a deep glacial lake in northern Alaska, were measured for the first time with the direct eddy covariance (EC) flux technique during six ice-free lake periods (2010–2015). CO2 flux estimates from the lake (daily average efflux of 16.7 ± 5.3 mmol m−2 d−1) were in good agreement with earlier estimates from 1975–1989 using different methods. CH4 effluxes in 2010–2015 (averaging 0.13 ± 0.06 mmol m−2 d−1) showed an interannual variation that was 4.1 times greater than median diel variations, but mean fluxes were almost one order of magnitude lower than earlier estimates obtained from single water samples in 1990 and 2011–2012. The overall global warming potential (GWP) of Toolik Lake is thus governed mostly by CO2 effluxes, contributing 86–93% of the ice-free period GWP of 26–90 g CO2,eq m−2. Diel variation in fluxes was also important, with up to a 2-fold (CH4) to 4-fold (CO2) difference between the highest nighttime and lowest daytime effluxes. Within the summer ice-free period, on average, CH4 fluxes increased 2-fold during the first half of the summer, then remained almost constant, whereas CO2 effluxes remained almost constant over the entire summer, ending with a linear increase during the last 1–2 weeks of measurements. Due to the cold bottom temperatures of this 26 m deep lake, and the absence of ebullition and episodic flux events, Toolik Lake and other deep glacial lakes are likely not hot spots for greenhouse gas emissions, but they still contribute to the overall GWP of the Arctic.