Methane: The record in polar ice cores
Methane: The record in polar ice cores
复制标题
甲烷：极地冰芯的记录
DOI：
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发表时间：
1982
期刊：
影响因子：
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通讯作者：
C. Chou
中科院分区：
文献类型：
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作者：
H. Craig;C. Chou
在Dye 3格陵兰冰芯中，被困空气中的甲烷混合比从1.25 ppmv下降到低于积雪-冰转变（1990年B. P.）到0.70 ppmv的基线值，深度为250米（距今500年）。在此水平以下至1950米深度（B）。P.）混合比在基线水平上似乎是恒定的，并且与Robbins等人（1973）关于700-2470年的南极冰的数据一致。在两个半球的冰帽和超过26000年，这些甲烷混合比的均匀性表明，无论绝对值是否正确地反映了真实的大气混合比与时间的关系，大气甲烷混合比在这个时间范围内基本上是恒定的。在250 m深度以上，被捕获的空气CH 4混合比线性增加到1000 m深度，然后急剧增加下面的雪冰过渡。混合比与年龄的轨迹强烈地偏离了过去15年的估计大气记录，但是当对积雪闭合时空气和冰的年龄差异进行校正时，冰芯数据相当精确地跟踪到最近的大气记录。因此，我们认为，这些数据正确地反映了过去的CH 4大气混合比。大气中甲烷浓度的增加始于公元1580年，到1918年达到10.40 ppmv，到1980年达到10.90 ppmv;在过去的400年中，与甲烷浓度增加相关的平衡温室效应约为0.23°C，以目前的增加速度，甲烷引起的变暖约为二氧化碳变暖效应的38%。
Methane mixing ratios in trapped air in the Dye 3 Greenland ice core decrease from 1.25 ppmv below the firn-ice transition (∼90 years B.P.) to a baseline value of 0.70 ppmv at a depth of ∼250 m (∼500 years B.P.). Below this level to a depth of 1950 m (∼27,000 years B. P.) the mixing ratio appears to be constant at the base-line level, and in agreement with data of Robbins et al. (1973) on 700-2470 year-old Antarctic ice. The uniformity of these CH4 mixing ratios in both hemispheric ice caps and over some 26 millennia indicates that, whether or not the absolute values correctly reflect the true atmospheric mixing ratios vs. time, the atmospheric CH4 mixing ratios were nevertheless essentially constant over this range of time. Above 250 m depth the trapped-air CH4 mixing ratios increase linearly up to ∼100 m depth, and then increase sharply just below the firn-ice transition. The mixing ratio vs. age trajectory is strongly offset from the estimated atmospheric record of the past 15 years, but when corrected for the ∼90 year difference in age of air and ice at firn closure, the ice-core data track quite precisely into the recent atmospheric record. Thus we believe that these data correctly reflect past CH4 atmospheric mixing ratios. The increase in atmospheric methane concentration begins at ∼1580 A.D. and amounts to ∼0.40 ppmv by 1918, and ∼0.90 ppmv by 1980; the equilibrium greenhouse warming associated with this increased CH4 concentration is about 0.23°C over the past 400 years, and at the current rate of increase the warming due to CH4 is about 38% of the CO2 warming effect.