Evidence for a link between climate and northern wetland methane emissions
Evidence for a link between climate and northern wetland methane emissions
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DOI：
10.1029/1999jd901100
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发表时间：
2000-02
影响因子：
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通讯作者：
D. Worthy;I. Levin;F. Hopper;M. Ernst;N. Trivett
中科院分区：
文献类型：
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作者：
D. Worthy;I. Levin;F. Hopper;M. Ernst;N. Trivett
湿地是大气甲烷(CH4)的重要来源，但这一来源的强度及其对气候潜在变化的敏感性仍不确定。利用加拿大Fraserdale(49°53‘N 81°34’W)和Alert(82°27‘N 62°31’W)两个观测站1990~1998年连续观测的CH4资料，估算了哈德逊湾低地(HBL)的CH4排放量。HBL占北部湿地总面积的10%。∼。利用Alert和Fraserdale之间的CH4浓度差、气团在HBL上的停留时间和对流边界层的混合高度，用一个概念上简单的方法计算了甲烷排放通量。用这种方法估算的1990年的排放率与同期在HBL内进行的飞机和塔架流量的经验测量结果吻合得很好，因此表明所用的方法是合理的。CH4的年排放速率在0.23~0.50tgCH4yr-1之间，远低于其他北部湿地的经验通量测量值。发现了Q10约为4的季节性温度敏感性。此外，观测到的排放年际变化与年气温的变化有很好的相关性，对应的灵敏度为Q107。也就是说，年气温每变化10℃，湿地排放的变化将是目前全球CH4模式(典型的Q101.5)所使用的Q10值的7倍。我们的发现表明，到目前为止，北方湿地的排放量可能被高估了，但由于预测的全球变暖，可能会显着增加。
Wetlands are an important source of atmospheric methane (CH 4 ), but the strength of this source and its sensitivity to potential changes in climate are still uncertain. In this study, continuous measurements from 1990 to 1998 of atmospheric CH 4 from the Canadian observational sites at Fraserdale (49°53'N 81°34'W) and Alert (82°27'N 62°31'W) are used to estimate CH 4 emissions from the Hudson Bay Lowland (HBL), a 320,000 km 2 semicontinuous wetland region in central Canada. The HBL comprises ∼ 10% of the total area of northern wetlands. A conceptually simple approach was used to calculate the methane emission flux using the CH 4 concentration difference between Alert and Fraserdale, the residence time of the air mass over the HBL, and the mixing height of the convective boundary layer. Emission rates estimated using this approach for 1990 compare well with empirical aircraft and tower flux measurements made within the HBL during the same time period, thus indicating that the methodology used is reasonable. Annual CH 4 emission rates range from 0.23 to 0.50 Tg CH 4 yr -1 and are much lower than many empirical flux measurements observed at other northern wetland sites. A seasonal temperature sensitivity with a Q 10 of about 4 was found. Moreover, the observed interannual variations in emissions are well correlated to variations in annual air temperatures corresponding to a sensitivity of Q 10 7. That is, a 10°C change in annual temperature would result in a sevenfold change in wetland emissions which is much larger than Q 10 values used in current global CH 4 models (typically Q 10 1.5). Our findings suggest that northern wetland emissions are probably overestimated to date but may increase significantly due to predicted global warming.