Analysis of seasonality and annual mean distribution of atmospheric potential oxygen (APO) in the Pacific region
Analysis of seasonality and annual mean distribution of atmospheric potential oxygen (APO) in the Pacific region
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太平洋地区大气势氧（APO）的季节性和年平均分布分析
DOI：
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发表时间：
2012
期刊：
影响因子：
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通讯作者：
Y. Nojiri
中科院分区：
文献类型：
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作者：
Y. Tohjima;C. Minejima;H. Mukai;T. Machida;H. Yamagishi;Y. Nojiri
根据在日本两个监测站和往返于日本和美国之间的商业货船上收集的烧瓶样品的大气O2/N2和CO2测量结果，我们提出了一组大气潜氧（APO = O2 + 1.1 × CO2）数据。加拿大和澳大利亚/新西兰。由于APO相对于陆地生物交换是不变的，它的变化主要反映了海气交换的时空分布。从2002-2008年的观测资料中，我们发现：（1）赤道附近的年平均值偏高;（2）北太平洋西北部的年平均值偏高且季节振幅较大;（3）西太平洋20-40°N处存在一个年平均低值的深槽。此外，纬度分布的时间观察到的季节性最大值和最小值显示出不对称的模式跨越赤道。将这些观测结果与NIES 99大气传输模式在一组气候学海洋O2和CO2通量场驱动下生成的一系列模拟APO进行比较，我们发现除了在中纬度观测到的深槽之外，其他观测结果都很好。不同输送机制和通量的模拟结果表明，海洋O2通量和大气输送之间的季节协变对观测到的北太平洋北方APO变化有显著贡献;纬向输送的季节变化也影响着季节循环中的纬向差异。基于最近修正的海洋CO2通量分布的模式比基于以前的CO2通量分布的模式更好地再现了南半球年平均APO的纬向梯度。在西太平洋36°N观测到的APO槽比用最近的pCO 2数据模拟的低约10个/meg，表明在该纬度区域存在额外的APO汇。事实上，在该区域（30-50°N，120-180°E）内，使用约30 Tmol yr-1的额外海洋O2汇通量进行的模式模拟相当好地再现了观测到的APO槽。
We present a data set of atmospheric potential oxygen (APO = O2 + 1.1 × CO2) based on the atmospheric O2/N2 and CO2measurements of flask samples collected at two monitoring stations in Japan and on commercial cargo ships sailing between Japan and U.S./Canada and Australia/New Zealand. Since APO is invariant with respect to the terrestrial biotic exchange, its variation mainly reflects the spatiotemporal distribution in the air‐to‐sea gas exchange. From the observed APO for the years 2002–2008, we find: (1) elevated annual mean values near the equator, (2) elevated annual mean values and large seasonal amplitudes in the northwestern North Pacific, and (3) a deep trough of low annual mean values at latitudes 20–40°N in the Western Pacific. In addition, latitudinal distributions in the timing of the observed seasonal maximum and minimum show asymmetric patterns across the equator. Comparing these observations with a series of simulated APO generated in the NIES99 atmospheric transport model driven by a set of climatological oceanic O2 and CO2 flux fields, we find a good agreement except for the observed deep trough at the midlatitude. Simulations with different transport mechanisms and fluxes reveal that the seasonal covariation between oceanic O2 flux and atmospheric transport contribute significantly to the observed APO variations in the northern North Pacific; also the seasonal variation in the meridional transport affects the latitudinal difference in the seasonal cycle. The observed latitudinal gradient of the annual mean APO in the Southern Hemisphere is better reproduced by the model based on the recently revised ocean CO2 flux distribution than that based on the previous CO2 flux distribution. The observed APO trough at 36°N in the Western Pacific is about 10 per meg lower than the simulation with the more recent pCO2 data, suggesting the existence of additional APO sinks in that latitudinal region. Indeed, a model simulation performed with an additional ocean O2 sink flux of about 30 Tmol yr−1 within the region (30–50°N, 120–180°E) reproduces considerably well the observed APO trough.