Using the deuterium isotope composition of permafrost meltwater to constrain thermokarst lake contributions to atmospheric CH4 during the last deglaciation
Using the deuterium isotope composition of permafrost meltwater to constrain thermokarst lake contributions to atmospheric CH4 during the last deglaciation
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DOI：
10.1029/2011jg001810
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发表时间：
2012-02-25
影响因子：
3.7
通讯作者：
Meyer, H.
中科院分区：
文献类型：
--
作者：
Brosius, L. S.;Anthony, K. M. Walter;Meyer, H.
热岩溶湖泊被认为是上一次冰川消融期间甲烷(CH4)的重要来源，当时大气中的甲烷浓度迅速上升。在这里，我们证明了来自永久冻土冰的融水是热喀斯特湖泊产生CH4的氢源，允许对西伯利亚和北美湖泊的三角洲D-CH4排放进行区域特定的重建。德尔塔D-CH4反映了地面冰形成时包含在地面冰中的降水的德尔塔D值在区域上的变化。晚更新世多年冻土地面冰是原生热岩溶湖泊CH4生成的主要氢源，而全新世多年冻土地面冰对后世湖泊CH4生成有贡献。我们发现阿拉斯加热岩溶湖三角洲D-CH4(-334+/-17‰)高于西伯利亚湖泊三角洲D-CH4(-381‰+/-18‰)。在去冰期期间，柏林纪湖泊的加权平均增量D-CH4值介于-385‰到-382‰之间。自下而上的估算表明，贝林期热喀斯特湖泊在年轻仙女木时期为大气贡献了15+/-4Tg CH4年(-1)，在前北冰洋时期为大气贡献了25+/-5Tg CH4年(-1)。这些估计得到了基于冰芯D-CH4和C-13(CH4)记录的独立的、自上而下的同位素质量平衡计算的支持。这两种方法都表明，热喀斯特湖泊和北方湿地一起是脱冰期CH4的重要来源。
Thermokarst lakes are thought to have been an important source of methane (CH4) during the last deglaciation when atmospheric CH4 concentrations increased rapidly. Here we demonstrate that meltwater from permafrost ice serves as an H source to CH4 production in thermokarst lakes, allowing for region-specific reconstructions of delta D-CH4 emissions from Siberian and North American lakes. delta D-CH4 reflects regionally varying delta D values of precipitation incorporated into ground ice at the time of its formation. Late Pleistocene-aged permafrost ground ice was the dominant H source to CH4 production in primary thermokarst lakes, whereas Holocene-aged permafrost ground ice contributed H to CH4 production in later generation lakes. We found that Alaskan thermokarst lake delta D-CH4 was higher (-334 +/- 17 parts per thousand) than Siberian lake delta D-CH4 (-381 +/- 18 parts per thousand). Weighted mean delta D-CH4 values for Beringian lakes ranged from -385 parts per thousand to -382 parts per thousand over the deglacial period. Bottom-up estimates suggest that Beringian thermokarst lakes contributed 15 +/- 4 Tg CH4 yr(-1) to the atmosphere during the Younger Dryas and 25 +/- 5 Tg CH4 yr(-1) during the Preboreal period. These estimates are supported by independent, top-down isotope mass balance calculations based on ice core delta D-CH4 and delta C-13(CH4) records. Both approaches suggest that thermokarst lakes and boreal wetlands together were important sources of deglacial CH4.