Limited contribution of permafrost carbon to methane release from thawing peatlands
Limited contribution of permafrost carbon to methane release from thawing peatlands
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DOI：
10.1038/nclimate3328
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发表时间：
2017-06
影响因子：
30.7
通讯作者：
Mark D. A. Cooper;Cristian Estop‐Aragonés;J. P. Fisher;A. Thierry;M. Garnett;D. Charman;J. Murton
中科院分区：
文献类型：
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作者：
Mark D. A. Cooper;Cristian Estop‐Aragonés;J. P. Fisher;A. Thierry;M. Garnett;D. Charman;J. Murton
模型预测，到2100年，北部高纬度地区永久冻土的融化将向大气释放数百亿吨碳(C)。对地球气候的影响在很大程度上取决于作为更强大的温室气体甲烷(CH4)而不是二氧化碳(CO2)释放的这种C的比例；即使CH4的排放仅占C排放的2%，它们也将贡献大约四分之一的气候强迫。在北部泥炭地，富含冰的永久冻土的融化会导致地表下沉(热岩溶)和内涝，使之前冻结的大量有机质(每平方米数十公斤C，参考文献1)暴露在厌氧条件下，并为永久冻土衍生的CH4释放创造理想的条件。在这里，我们显示，与预期相反，尽管从加拿大北部正在融化的泥炭地记录到大量的CH4通量(>；20 g CH4m−2yr−1)，但只有少量来自之前冻结的C(<；2 g CH4m−2yr−1)。相反，通量是由最近输入的C的厌氧分解驱动的。我们的结论是，融化引起的地表湿度和湿地面积的变化，而不是先前冻结的C的厌氧分解，可能决定了多年冻土融化对北部泥炭地CH4排放的影响。
Models predict that thaw of permafrost soils at northern high latitudes will release tens of billions of tonnes of carbon (C) to the atmosphere by 2100 (refs ,,). The effect on the Earth’s climate depends strongly on the proportion of this C that is released as the more powerful greenhouse gas methane (CH4), rather than carbon dioxide (CO2) (refs ,); even if CH4emissions represent just 2% of the C release, they would contribute approximately one-quarter of the climate forcing. In northern peatlands, thaw of ice-rich permafrost causes surface subsidence (thermokarst) and water-logging, exposing substantial stores (tens of kilograms of C per square meter, ref. ) of previously frozen organic matter to anaerobic conditions, and generating ideal conditions for permafrost-derived CH4release. Here we show that, contrary to expectations, although substantial CH4fluxes (>20 g CH4m−2yr−1) were recorded from thawing peatlands in northern Canada, only a small amount was derived from previously frozen C (<2 g CH4m−2yr−1). Instead, fluxes were driven by anaerobic decomposition of recent C inputs. We conclude that thaw-induced changes in surface wetness and wetland area, rather than the anaerobic decomposition of previously frozen C, may determine the effect of permafrost thaw on CH4emissions from northern peatlands.