Tracing Water Masses and Assessing Boundary Scavenging Intensity With Beryllium Isotopes in the Northern South China Sea
Tracing Water Masses and Assessing Boundary Scavenging Intensity With Beryllium Isotopes in the Northern South China Sea
复制标题
南海北部铍同位素追踪水团并评估边界清除强度
DOI：
10.1029/2021jc017236
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发表时间：
2021-07-01
影响因子：
3.6
通讯作者：
Zhou, L. P.
中科院分区：
文献类型：
--
作者：
Kong, W. Y.;Zhou, L. P.
宇宙成因放射性核素Be-10及其稳定同位素Be-9可用作水团混合的示踪剂，但这种应用在公海和边缘海都很少见。本文报道了南海北方从陆架到深盆沿着剖面的表层和水柱中溶解态Be-9和Be-10的浓度分布。表层沃茨中Be-9和Be-10的浓度范围分别为8.8-43.6 pmol/kg和118-576 atoms/g。南海北方Be-9主要来源于河流沃茨，而Be-10主要来自西太平洋，导致最接近吕宋海峡的Be-10/Be-9比值最高，为10.9 × 10（-8）。在深度剖面上，Be-9浓度沿着向南逐渐降低，Be-10浓度逐渐升高，最大值出现在A10站2,843 m深度处，为1,237 atoms/g。Be-10/Be-9比值的解释考虑到水混合和边界清除，这揭示了入侵黑潮的分支（>7.7 x 10（-8））和深气旋流（>8.9 x 10（-8））的证据。箱形模型计算出Be-10的沉降通量约为1，167 atoms/m（2）/s，是大气沉降通量的4.6倍，表明Be-10的边界清除活跃。Be-10在南海北方深水区的滞留时间大于79年。铍同位素作为水团示踪剂，在端元分化较好的盆地中具有广泛的应用前景。
The cosmogenic radionuclide Be-10 and its stable isotope Be-9 can be used as a tracer for water mass mixing, but such applications are rare in both open oceans and marginal seas. Here we report distributions of dissolved Be-9 and Be-10 concentrations of the seawater in the surface and water columns along a section from shelf to deep basin in the northern South China Sea (SCS). The concentrations of Be-9 and Be-10 in surface waters range between 8.8-43.6 pmol/kg and 118-576 atoms/g, respectively. The Be-9 in the northern SCS is dominantly sourced from river waters, while Be-10 has a prominent input from the western Pacific, resulting in the highest Be-10/Be-9 ratio of 10.9 x 10(-8) closest to the Luzon Strait. Along the depth section, the Be-9 concentrations decrease southward while Be-10 concentrations increase with the maximum value of 1,237 atoms/g occurring at 2,843 m depth of Station A10. The Be-10/Be-9 ratios are interpreted with consideration of water mixing and boundary scavenging, which reveal evidence of a branch of the intruding Kuroshio Current (>7.7 x 10(-8)) in subsurface water and a deep cyclonic current (>8.9 x 10(-8)). A box model yields a sedimentation flux of Be-10 around 1,167 atoms/m(2)/s, that is, 4.6 times of the atmospheric deposition flux, pointing to active boundary scavenging of Be-10. The residence time of Be-10 in the deep water is estimated to be longer than 79 years in the northern SCS. The beryllium isotopes as a water mass tracer will find wide applications in basins where the endmembers are sufficiently differentiated.