Circulation, eddies, oxygen, and nutrient changes in the eastern tropical South Pacific Ocean
Circulation, eddies, oxygen, and nutrient changes in the eastern tropical South Pacific Ocean
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DOI：
10.5194/os-11-455-2015
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发表时间：
2015-01-01
期刊：
影响因子：
3.2
通讯作者：
Fischer, T.
中科院分区：
文献类型：
--
作者：
Czeschel, R.;Stramma, L.;Fischer, T.
热带南太平洋东部（ETSP）存在一个大型地下缺氧区。2012年11月/12月赤道东太平洋和秘鲁沿海的大规模环流显示了赤道海流系统、东部边界流和副热带环流北方的影响。2012年11月，赤道暗流（EUC）的中心深度为250米，比以前的观测更深。2012年12月，赤道水在秘鲁-智利暗流（PCUC）中向东南方向输送，平均输送量为1.4 Sv。在氧气最小区（OMZ），流动与OMZ的极向侧的强涡流活动重叠。停泊深度为400 m的浮标显示，赤道通道中深度的快速向西流动和OMZ中的缓慢流动。带有氧传感器的浮子清楚地显示了带有氧异常的漩涡的通过。在海洋上层的长期浮标观测结果表明，在南纬18度左右，群落净生产量估计为16.7 mmol C m（-3）yr（-1），外推到年速率，混合层以下的时间段为7.7 mmol C m（-3）yr（-1）。重复船段之间的氧气差异受到年代际太平洋涛动（IPO）、厄尔尼诺阶段、季节变化和涡旋的影响，因此必须小心解释。自1976年以来，赤道以南海洋上层的氧气减少与硝酸盐、磷酸盐和部分硅酸盐的增加有关。
A large subsurface oxygen deficiency zone is located in the eastern tropical South Pacific Ocean (ETSP). The large-scale circulation in the eastern equatorial Pacific and off the coast of Peru in November/December 2012 shows the influence of the equatorial current system, the eastern boundary currents, and the northern reaches of the subtropical gyre. In November 2012 the equatorial undercurrent (EUC) is centered at 250 m depth, deeper than in earlier observations. In December 2012, the equatorial water is transported southeastward near the shelf in the Peru-Chile undercurrent (PCUC) with a mean transport of 1.4 Sv. In the oxygen minimum zone (OMZ), the flow is overlaid with strong eddy activity on the poleward side of the OMZ. Floats with parking depth at 400 m show fast westward flow in the mid-depth equatorial channel and sluggish flow in the OMZ. Floats with oxygen sensors clearly show the passage of eddies with oxygen anomalies. The long-term float observations in the upper ocean lead to a net community production estimate at about 18 degrees S of up to 16.7 mmol C m(-3) yr(-1) extrapolated to an annual rate and 7.7 mmol C m(-3) yr(-1) for the time period below the mixed layer. Oxygen differences between repeated ship sections are influenced by the Interdecadal Pacific Oscillation (IPO), by the phase of El Nino, by seasonal changes, and by eddies, and hence have to be interpreted with care. At and south of the Equator the decrease in oxygen in the upper ocean since 1976 is related to an increase in nitrate, phosphate, and in part silicate.