Estimation of the concentrations of greenhouse gases in ancient air using ice core analysis

独立开发了干湿空气提取CO_2、CH_4和N_2O浓度及极地冰芯CO_2 δ ^<13>C的精确分析技术，以重建其古代水平。目前测量的总体精度，包括空气抽取，估计CO_2优于*1.0 ppmv， CH_4优于*10 ppbv， N_2O优于*2ppbv， δ ^<13>C优于0.05*。利用这些实验技术，对三个冰芯进行了分析，其中两个来自南极洲，一个来自格陵兰岛。本文的研究结果总结如下：1。CO_2、CH_4和N_2O浓度几乎在整个全新世时期都相当稳定，波动较小。然而，在250年后，由于人类活动，这些气体的浓度随着时间的推移而增加。南极Yamato山附近冰芯的CO_2、CH_4和N_2O浓度明显低于工业时代前的全新世值，表明该冰芯形成于冰期。在冰期，CO_2浓度与d13C的变化几乎是不相一致的，这可能意味着通过浮游植物活动在大气和海洋之间进行了CO_2交换。工业化前/农业前，北极地核的CH_4浓度高于南极地核的54*10 ppbv，表明北半球的CH_4自然源比南半球强，反映了北方陆地比南方陆地的范围更大。据估计，目前南北高纬度地区大气中CH_4的浓度差几乎是我们在前工业/前农业时代测量到的浓度差的三倍。由此可见，大量的CH_4正从人为的CH_4源释放到大气中，特别是在北半球，而/或北半球的OH自由基减少得更快，这可能是由于化石燃料燃烧增加了大气CO浓度。少

Precise analysis technique with dry and wet air extractions for the CO_2, CH_4 and N_2O concentrations and delta^<13>C of CO_2 from polar ice core was newly developed independently to reconstruct their ancient levels. The overall precision of the present measurements, including air extraction, was estimated to be better than *1.0 ppmv for CO_2, *10 ppbv for CH_4, *2ppbv for N_2O and 0.05* for delta^<13>C. By using these experimentaltechnique, three ice cores, two from the Antarctica one from Greenland, were analyzed. The results obtained in this study are summarized as follows:1. The CO_2,CH_4 and N_2O concentrations were fairly stable during almost entire period of the Holocene with small fluctuations of the concentration. However, after 250 years BP, the concentrations of these gases increased with time due to human activities.2. The CO_2,CH_4 and N_2O concentrations from an ice core near the Yamato Mountains, Antarctica were obviously lower than the pre-industrial Holocene values, s … More uggesting that this core was formed in the glacial period. During the glacial period, the CO_2 concentrations varied almost out of phase with d13C, which may imply that CO_2 exchange occurred between the atmosphere and the oceans through phytoplankton activities.3. The pre-industrial/pre-agricultural levels of the CH_4 concentration from the Arctic core were higher than 54*10 ppbv than those from the Antarctic core, which is suggested that natural CH_4sources had been stronger in the northern hemisphere than in the southern hemisphere, reflecting the greater extent of boreal compared with austral lands. The present concentration difference of atmospheric CH_4 between northern and southern high latitudes was estimated to be almost three time as much as we have measured for the pre-industrial/pre-agricultural era. From this fact, it was suggested that a large amount of CH_4 was being released into the atmosphere from anthropogenic CH_4 sources especially in the northern hemisphere and/or OH radicals have decreased more rapidly in the northern hemisphere, perhaps due to an increase of the atmospheric CO concentration by fossil fuel combustion. Less