Apparent enhancement of 234Th-based particle export associated with anticyclonic eddies
Apparent enhancement of 234Th-based particle export associated with anticyclonic eddies
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DOI：
10.1016/j.epsl.2013.07.039
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发表时间：
2013-11
影响因子：
5.3
通讯作者：
K. Zhou;M. Dai;S. Kao;Lei Wang;P. Xiu;F. Chai;Jiwei Tian;Yang Liu
中科院分区：
文献类型：
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作者：
K. Zhou;M. Dai;S. Kao;Lei Wang;P. Xiu;F. Chai;Jiwei Tian;Yang Liu
中尺度涡旋对海洋地球化学变化的调节作用日益受到人们的重视。一般认为，反气旋性涡旋的特征是在其核心区有下降流，这可能会抑制粒子的输出。在这里，通过考虑亚中尺度域，我们证明，颗粒输出可能会交替增强反气旋涡旋的基础上进行的研究，在贫营养的北方南海盆地。我们研究了粒子通量与三个相干反气旋涡旋使用天然存在的放射性核素234 Th。当应用一维稳态模型，234 Th和其衍生的颗粒有机碳（POC）通量在所有三个涡核分别高1.9和1.6倍，相对于那些在非涡区。然而，涡分辨环流数值模式显示，与反气旋涡复杂的亚中尺度环流。值得注意的是，动态的相互作用发生在亚中观尺度，可能会导致平流到涡核心的边缘，在那里的234 Th赤字升高，由于较高的颗粒生产和出口，可能是由上涌的刺激在边缘。因此，我们建议，从一维模式得到的增强粒子通量沿着垂直地平线在涡核似乎只是变化，和水平平流之间的涡核和边缘应考虑在通量估计。事实上，通过对整个反气旋涡旋系统中多个剖面中的234 Th亏损进行积分，我们得出了100米水平线处的平均234 Th通量为938 dpm m− 2 d− 1，相当于POC通量为3.69 mmol C m− 2 d− 1。这一出口水平是参考中心的1.6倍。
It is increasingly recognized that mesoscale eddies play an important role in modulating the variability of ocean biogeochemistry. It is commonly believed that contrary to cyclonic eddies, anticyclonic eddies are characterized by downwelling at their core regime, which may suppress particle export. Here, by considering submesoscale domains we demonstrate that particle export might be alternatively enhanced in anticyclonic eddies on the basis of a study carried out in the oligotrophic northern South China Sea basin. We examined particle fluxes associated with three coherent anticyclonic eddies using the naturally occurring radionuclide 234 Th. When applying a 1D steady-state model, 234 Th and its derived particulate organic carbon (POC) fluxes in all three eddy cores were 1.9-and 1.6-fold higher, respectively, relative to those in the non-eddy region. However, an eddy-resolving circulation numerical model showed complex submesoscale circulations associated with the anticyclonic eddy. Notably, dynamic interactions occurred at submesoscales that might induce advection into the eddy core from the edge, where the 234 Th deficit was elevated owing to higher particle production and export, probably stimulated by upwelling at the edges. We suggest therefore that enhanced particle fluxes derived from the 1D model along the vertical horizon at eddy cores only appeared to be changes, and that horizontal advection between the eddy core and edge should be taken into consideration in the flux estimation. Indeed, by integrating the 234 Th deficit among multiple profiles in the entire anticyclonic eddy system, we derived an average 234 Th flux of 938 dpm m− 2 d− 1 at the 100-m horizon, equivalent to a POC flux of 3.69 mmol C m− 2 d− 1. This export level was 1.6-fold higher than that from the reference sites.