Neodymium isotopic characterization of Ross Sea Bottom Water and its advection through the southern South Pacific
Neodymium isotopic characterization of Ross Sea Bottom Water and its advection through the southern South Pacific
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DOI：
10.1016/j.epsl.2015.03.011
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发表时间：
2015-06-01
影响因子：
5.3
通讯作者：
Gersonde, Rainer
中科院分区：
文献类型：
--
作者：
Basak, Chandranath;Pahnke, Katharina;Gersonde, Rainer
自国际地球物理研究计划启动以来，研究全球海洋中微量元素及其同位素分布的研究显著增加。尽管进行了这一大规模努力，但高纬度南太平洋，特别是南极极锋以北地区的钕同位素(ND-143/ND-144，埃(ND))和浓度([ND])的分布仍未得到充分研究。本文报道了南美洲和新西兰之间的南太平洋以及整个南极锋面系统的11个垂直水柱剖面的溶解Nd同位素和浓度。结果证实，罗斯海底水(RSBW)由一个近似于-7的epsilon(ND)值表示，并首次表明这些ND特征可以追溯到东南太平洋，直到与周围环境的下绕极深水(LCDW)的逐渐混合稀释了APP以北的这一信号。也就是说，epsilon(ND)在RSBW中的行为是保守的，这为研究过去的RSBW行为开辟了一条道路。在APP以南，表层[ND]很高，并随着深度的增加而增加，但在1000m以下几乎保持不变。这种垂直和空间的[ND]模式遵循南大洋向南的浅海密度表面，因此表明富Nd的深水上涌向上层海洋供应Nd。由于蛋白石产量减少和季节性海冰覆盖而导致的低粒子丰度可能有助于维持APF以南的上层大洋[ND]。这表明，在APF以南的南太平洋，[ND]的横向输送成分占主导地位，对ND浓度的垂直控制减弱。(C)2015爱思唯尔B.V.保留所有权利。
Since the inception of the international GEOTRACES program, studies investigating the distribution of trace elements and their isotopes in the global ocean have significantly increased. In spite of this large-scale effort, the distribution of neodymium isotopes (Nd-143/Nd-144, epsilon(Nd)) and concentrations ([Nd]) in the high latitude South Pacific is still understudied, specifically north of the Antarctic Polar Front (APF). Here we report dissolved Nd isotopes and concentrations from 11 vertical water column profiles from the South Pacific between South America and New Zealand and across the Antarctic frontal system. Results confirm that Ross Sea Bottom Water (RSBW) is represented by an epsilon(Nd) value of similar to-7, and for the first time show that these Nd characteristics can be traced into the Southeast Pacific until progressive mixing with ambient Lower Circumpolar Deep Water (LCDW) dilutes this signal north of the APP. That is, epsilon(Nd) behaves conservatively in RSBW, opening a path for studies of past RSBW behavior.Neodymium concentrations show low surface concentrations and a linear increase with depth north of the APF. South of the APP, surface [Nd] is high and increases with depth but remains almost constant below similar to 1000 m. This vertical and spatial [Nd] pattern follows the southward shoaling density surfaces of the Southern Ocean and hence suggests supply of Nd to the upper ocean through upwelling of Nd-rich deep water. Low particle abundance due to reduced opal production and seasonal sea ice cover likely contributes to the maintenance of the high upper ocean [Nd] south of the APF. This suggests a dominant lateral transport component on [Nd] and a reduced vertical control on Nd concentrations in the South Pacific south of the APF. (C) 2015 Elsevier B.V. All rights reserved.