Reviews and syntheses: Present, past, and future of the oxygen minimum zone in the northern Indian Ocean
Reviews and syntheses: Present, past, and future of the oxygen minimum zone in the northern Indian Ocean
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DOI：
10.5194/bg-17-6051-2020
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发表时间：
2020-12
期刊：
影响因子：
4.9
通讯作者：
T. Rixen;G. Cowie;B. Gaye;J. Goes;Helga do Rosário Gomes;R. Hood;Z. Lachkar;Henrike Schmidt;J. Segschneider;Arvind Singh
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文献类型：
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作者：
T. Rixen;G. Cowie;B. Gaye;J. Goes;Helga do Rosário Gomes;R. Hood;Z. Lachkar;Henrike Schmidt;J. Segschneider;Arvind Singh
抽象。海洋中溶解氧浓度的下降被认为是对海洋生态系统的主要威胁之一，因为它们危及高等生物的生长。它们还改变了与碳循环和气候密切相关的海洋氮循环。虽然高等生物一般开始遭受氧浓度为0和1000的痛苦，但考虑到季风每年两次逆转海洋表面环流，并在几周内将阿拉伯海的大片地区从贫营养的海洋沙漠变成海洋中最具生产力的地区之一，0.05 µM是非常不寻常的。因此，OMZ中氧浓度的极低可变性意味着物理氧供应和生物氧消耗之间的稳定平衡，其包括负反馈机制，例如在降低氧浓度时降低氧消耗（例如，减少呼吸）。较低的生物耗氧量也被认为是负责一个不太激烈的OMZ在孟加拉湾。根据数值模型的结果，减少物理氧气供应，通过从南方流入的水团加强了阿拉伯海OMZ在过去的6000年，而减少氧气供应，通过从北方流入的波斯湾水加强了OMZ今天在全球变暖的反应。第一个是支持来自沉积记录的数据，后者同意在过去几十年中在阿拉伯海的氧浓度下降和功能性缺氧的蔓延的意见。在阿拉伯海，氧气浓度的下降似乎已经在水层生态系统结构中引发了一种状态转变，这种趋势也见于底栖生态系统。地球化学循环的后果尚不清楚，除了全球地球系统模型中的中尺度特征代表性差之外，还降低了对北方印度洋未来OMZ发展估计的可靠性。
Abstract. Decreasing concentrations of dissolved oxygen in the ocean are considered one of the main threats to marine ecosystems as they jeopardize the growth of higher organisms. They also alter the marine nitrogen cycle, which is strongly bound to the carbon cycle and climate. While higher organisms in general start to suffer from oxygen concentrations 0 and ∼ 0.05 µM is highly extraordinary considering that the monsoon reverses the surface ocean circulation twice a year and turns vast areas of the Arabian Sea from an oligotrophic oceanic desert into one of the most productive regions of the oceans within a few weeks. Thus, the comparably low variability of oxygen concentration in the OMZ implies stable balances between the physical oxygen supply and the biological oxygen consumption, which includes negative feedback mechanisms such as reducing oxygen consumption at decreasing oxygen concentrations (e.g., reduced respiration). Lower biological oxygen consumption is also assumed to be responsible for a less intense OMZ in the Bay of Bengal. According to numerical model results, a decreasing physical oxygen supply via the inflow of water masses from the south intensified the Arabian Sea OMZ during the last 6000 years, whereas a reduced oxygen supply via the inflow of Persian Gulf Water from the north intensifies the OMZ today in response to global warming. The first is supported by data derived from the sedimentary records, and the latter concurs with observations of decreasing oxygen concentrations and a spreading of functional anoxia during the last decades in the Arabian Sea. In the Arabian Sea decreasing oxygen concentrations seem to have initiated a regime shift within the pelagic ecosystem structure, and this trend is also seen in benthic ecosystems. Consequences for biogeochemical cycles are as yet unknown, which, in addition to the poor representation of mesoscale features in global Earth system models, reduces the reliability of estimates of the future OMZ development in the northern Indian Ocean.