Diapycnal oxygen supply to the tropical North Atlantic oxygen minimum zone
Diapycnal oxygen supply to the tropical North Atlantic oxygen minimum zone
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DOI：
10.5194/bg-10-5079-2013
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发表时间：
2013-01-01
期刊：
影响因子：
4.9
通讯作者：
Visbeck, M.
中科院分区：
文献类型：
--
作者：
Fischer, T.;Banyte, D.;Visbeck, M.
在非洲西北部外海开阔海洋氧气最小区（OMZ），消耗氧气的补充是通过穿越和沿着密度面的氧气输运，即穿膜供氧和等密度供氧来实现的。在这里，使用2008年至2010年的一组大型观测氧气剖面和纵摇池混合数据研究纵摇池的氧气供应。从不同的来源推断：（一）一个大规模的示踪剂释放实验，（二）微结构配置文件，和（三）船载声流测量加上密度配置文件。根据这些测量结果，从150米到500米的研究深度段的平均透环扩散率估计为1 × 10（-5）m（2）s（-1），95%置信下限和上限分别为0.8 × 10（-5）m（2）s（-1）和1.4 × 10（-5）m（2）s（-1）。在这个深度范围内的Diapycnal扩散主要是由湍流引起的，并没有显着的垂直梯度。横隔混合被认为有助于大幅度的OMZ的氧气供应。在OMZ核心内，1.5 μ mol kg（-1）yr（-1）的氧气通过横隔混合提供，约占总需求量的三分之一。这种通过底辟混合提供的氧气来自于在大洋区上方的中央上层和大洋区下方的南极中层水层内横向提供的氧气。由于存在一个单独的浅氧最低在整个研究区域的深度约100米，有没有从表层到中央水层的净垂直氧通量。因此，OMZ的所有氧气供应都与远程路径相关。
The replenishment of consumed oxygen in the open ocean oxygen minimum zone (OMZ) off northwest Africa is accomplished by oxygen transport across and along density surfaces, i.e. diapycnal and isopycnal oxygen supply. Here the diapycnal oxygen supply is investigated using a large observational set of oxygen profiles and diapycnal mixing data from years 2008 to 2010. Diapycnal mixing is inferred from different sources: (i) a large-scale tracer release experiment, (ii) microstructure profiles, and (iii) shipboard acoustic current measurements plus density profiles. From these measurements, the average diapycnal diffusivity in the studied depth interval from 150 to 500m is estimated to be 1x10(-5) m(2) s(-1), with lower and upper 95% confidence limits of 0.8x10(-5) m(2) s(-1) and 1.4x10(-5) m(2) s(-1). Diapycnal diffusivity in this depth range is predominantly caused by turbulence, and shows no significant vertical gradient. Diapycnal mixing is found to contribute substantially to the oxygen supply of the OMZ. Within the OMZ core, 1.5 mu mol kg(-1) yr(-1) of oxygen is supplied via diapycnal mixing, contributing about one-third of the total demand. This oxygen which is supplied via diapycnal mixing originates from oxygen that has been laterally supplied within the upper Central Water layer above the OMZ, and within the Antarctic Intermediate Water layer below the OMZ. Due to the existence of a separate shallow oxygen minimum at about 100m depth throughout most of the study area, there is no net vertical oxygen flux from the surface layer into the Central Water layer. Thus all oxygen supply of the OMZ is associated with remote pathways.