Quantification of CO2 budget of atmosphere and ocean by two CO2 exchange models and analysis of global CO2 circulation

全球变暖对当前人类活动产生了重要影响。二氧化碳（CO2）是最重要的温室气体之一，与海气交换和全球碳循环有关。海气CO2通量的估算在全球碳循环和气候研究中具有重要意义。大气和海洋之间的CO2通量由CO2分压差（pCO2）乘以CO2气体交换系数估算，CO2气体交换系数是估算大气-海洋CO2通量的重要参数之一。目前已经提出了几种计算气体交换系数的气体传递模型，但由于气体交换系数的测量困难，目前对CO2气体传递模型进行评价并不容易。在本研究中，我们建立了“海气交换反馈模型”来描述海气界面引起的气体交换过程，该模型可以估计海水中pCO2的时间变化。结果表明，在7 ~ 15m/s风速范围内，典型CO2交换系数的精度为1%。其次，我们分析了进入海洋表面的CO2的表面总CO2（TCO2）时间序列的变化，我们建立了另一个“TCO2变化分析”模型。根据该模型，地表TCO2变化可分为大气CO2通量的影响和上升流、生物活动等其他影响。此外，我们将“TCO2变化分析”模型扩展到全球区域。结果表明，全球海洋表面CO2的变化以大气和海洋的非海气CO2通量为主，其值约为2 （μmol/kg/月）。在北半球，它也倾向于霸道。

Global warming has imposed an important impact on people activities at the present time. Carbon dioxide(CO2), one of the most important green house gases, is associated with air-sea gas exchange and global carbon circulation. The estimation of air-sea CO2 flux is very important in global carbon circulation and climate research. The flux of CO2 between the atmosphere and the ocean is estimated by the partial pressure of CO2(pCO2) difference multiplied by CO2 gas exchange coefficient which is one of the very important parameters in estimating air-sea CO2 flux. Several gas transfer models which calculates gas exchange coefficient have been proposed, but it is not easy to evaluate CO2 gas transfer models at the present time due to the difficulties of gas exchange coefficient measurement.In this study, we developed "Air-sea carbon dioxide exchange feedback model" to describe gas exchange processes caused at the air-sea interface, which can estimate the temporal variation of pCO2 in the seawater. As a result, typical CO2 exchange coefficients had accuracy of 1% within wind speed about 7-15m/s.Next, we analyzing the variation of the time series of the surface total CO2(TCO2) about the CO2 taken into an oceanic surface, we have made another one model of the "TCO2 variation analysis". According to this model, surface TCO2 change was able to be divided into the influence from CO2 flux from atmosphere and other influences that are the upwelling and the biological activities. In addition, we enhanced the model of the "TCO2 variation analysis" to global area. As a result, the variation of the surface TCO2 in global ocean is predominant of not air-sea CO2 flux from atmosphere and ocean, and it's value is about 2 (μmol/kg/month). In North hemisphere, it also tends to be domineering.