Oxygen variance and meridional oxygen supply in the Tropical North East Atlantic oxygen minimum zone
Oxygen variance and meridional oxygen supply in the Tropical North East Atlantic oxygen minimum zone
复制标题
热带东北大西洋氧气最低区的氧气变化和经向氧气供应
作者：
J. Hahn;P Brandt;R. Greatbatch;G. Krahmann;A. Körtzinger
平均海洋氧浓度的分布是由通气和消耗之间的平衡引起的。在热带太平洋和大西洋东部，这种平衡在中间深度产生了扩展的氧气最小区（OMZ）。本文利用沿着23°W经线穿过热带东北大西洋（TNEA）OMZ的船载和系泊观测资料，分析了海洋水文和流速资料，研究了氧变率的分布和产生。通过应用扩展的Osween-Cox模型，中尺度搅拌和diapycnal混合在产生增强的氧变率，发现在南部和上部边界的OMZ，各自的作用进行了量化。从通风良好的赤道区域到OMZ核心，观测到一个向北的涡旋驱动的氧通量，其发散对应于OMZ核心深度约2.4 μmol kg−1年−1的氧供应。以上OMZ核心，中尺度涡旋的行为重新分配低和高氧沃茨与向西和向东的电流，分别。在这里，发现当地氧气供应的绝对值>10 μmol kg−1年−1，可能被平均纬向平流平衡。结合我们的研究结果与最近的研究，一个完善的氧气预算TNEA OMZ的。涡流驱动的双腔氧气供应量占平衡估计氧气消耗量所需供应量的50%以上。OMZ中的氧趋势，如由几十年氧下降给出的，在OMZ核心上方最大，并且代表氧收支的实质性不平衡，达到约20%的涡流驱动的氧供应的幅度。
The distribution of the mean oceanic oxygen concentration results from a balance between ventilation and consumption. In the eastern tropical Pacific and Atlantic, this balance creates extended oxygen minimum zones (OMZ) at intermediate depth. Here, we analyze hydrographic and velocity data from shipboard and moored observations, which were taken along the 23°W meridian cutting through the Tropical North East Atlantic (TNEA) OMZ, to study the distribution and generation of oxygen variability. By applying the extended Osborn–Cox model, the respective role of mesoscale stirring and diapycnal mixing in producing enhanced oxygen variability, found at the southern and upper boundary of the OMZ, is quantified. From the well-ventilated equatorial region toward the OMZ core a northward eddy-driven oxygen flux is observed whose divergence corresponds to an oxygen supply of about 2.4 μmol kg−1 year−1 at the OMZ core depth. Above the OMZ core, mesoscale eddies act to redistribute low- and high-oxygen waters associated with westward and eastward currents, respectively. Here, absolute values of the local oxygen supply >10 μmol kg−1 year−1 are found, likely balanced by mean zonal advection. Combining our results with recent studies, a refined oxygen budget for the TNEA OMZ is derived. Eddy-driven meridional oxygen supply contributes more than 50 % of the supply required to balance the estimated oxygen consumption. The oxygen tendency in the OMZ, as given by the multidecadal oxygen decline, is maximum slightly above the OMZ core and represents a substantial imbalance of the oxygen budget reaching about 20 % of the magnitude of the eddy-driven oxygen supply.
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