Seasonal variations in the atmospheric O2/N2 ratio in relation to the kinetics of air‐sea gas exchange
Seasonal variations in the atmospheric O2/N2 ratio in relation to the kinetics of air‐sea gas exchange
复制标题
大气 O2/N2 比率的季节变化与海气交换动力学的关系
DOI：
10.1029/97gb02339
复制
发表时间：
1998
影响因子：
5.2
通讯作者：
M. Heimann
中科院分区：
文献类型：
--
作者：
R. Keeling;B. Stephens;R. Najjar;S. Doney;D. Archer;M. Heimann
据报告，在北方和南半球的9个基线地点观测了大气O2/N2比率的季节性变化。同时CO2测量用于校正陆地生物交换O2对O2/N2循环的影响，从而允许计算由于海洋交换O2和N2的循环的剩余部分。北方半球的剩余海洋循环与南半球的循环几乎完全不同相。两个半球的最大值都出现在夏季。在两个半球，中纬度海平面站显示出振幅最大和相位最早的周期。在高纬度台站观测到的振幅较小，在热带台站观测到的振幅要小得多。提出了一个模拟大气O2/N2循环的海洋部分的模式，该模式由TM 2大气示踪剂输送模式[Heimann，1995]组成，该模式在下边界由来自观测到的表面沃茨中O2饱和度异常的O2通量和来自净海气热通量的N2通量驱动。通过调整海气交换速率，将O2异常与O2通量联系起来，对模型进行了优化，以拟合观测到的大气O2/N2循环。最佳拟合对应于31°N以北海洋的时空平均交换速度为24±6 cm/hr，31° S以南海洋的时空平均交换速度为29±12 cm/hr。这些速度与Wanninkhof [1992]的海气交换速度公式结合欧洲中期天气预报中心风[吉布森等人，1997年]，但大于交换速度预期的利斯和Merlivat [1986]关系使用相同的风。这些结果意味着，与CO2一样，O2的气体交换速度可能会在开阔海洋中通过在用于推导利斯和Merlivat关系的实验中没有系统考虑的过程而得到增强。
Observations of seasonal variations in the atmospheric O2/N2 ratio are reported at nine baseline sites in the northern and southern hemispheres. Concurrent CO2 measurements are used to correct for the effects of land biotic exchanges of O2 on the O2/N2 cycles thus allowing the residual component of the cycles due to oceanic exchanges of O2 and N2 to be calculated. The residual oceanic cycles in the northern hemisphere are nearly diametrically out of phase with the cycles in the southern hemisphere. The maxima in both hemispheres occur in summer. In both hemispheres, the middle‐latitude sea level stations show the cycles with largest amplitudes and earliest phasing. Somewhat smaller amplitudes are observed at the high‐latitude stations, and much smaller amplitudes are observed at the tropical stations. A model for simulating the oceanic component of the atmospheric O2/N2 cycles is presented consisting of the TM2 atmospheric tracer transport model [Heimann, 1995] driven at the lower boundary by O2 fluxes derived from observed O2 saturation anomalies in surface waters and by N2 fluxes derived from the net air‐sea heat flux. The model is optimized to fit the observed atmospheric O2/N2 cycles by adjusting the air‐sea gas‐exchange velocity, which relates O2 anomaly to O2 flux. The optimum fit corresponds to spatially and temporally averaged exchange velocities of 24±6 cm/hr for the oceans north of 31°N and 29±12 cm/hr for the oceans south of 31° S. These velocities agree to within the uncertainties with the gas‐exchange velocities expected from the Wanninkhof [1992] formulation of the air‐sea gas‐exchange velocity combined with European Centre for Medium‐Range Weather Forecasts winds [Gibson et al., 1997] but are larger than the exchange velocities expected from the Liss and Merlivat [1986] relation using the same winds. The results imply that the gas‐exchange velocity for O2, like that of CO2, may be enhanced in the open ocean by processes that were not systematically accounted for in the experiments used to derive the Liss and Merlivat relation.