Nd isotopic composition in the central North Pacific
Nd isotopic composition in the central North Pacific
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DOI：
10.1016/j.gca.2009.05.058
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发表时间：
2009-08-15
影响因子：
5
通讯作者：
Ebihara, Mitsuru
中科院分区：
文献类型：
--
作者：
Amakawa, Hiroshi;Sasaki, Kazunori;Ebihara, Mitsuru
本文测定了北太平洋西部至中部海水Nd浓度和同位素组成的三个垂直剖面，在亚北极海区，在大于500 m的深度，有一个Nd同位素组成的垂直剖面与以往报道的大多数剖面没有区别。这些数据表明，在亚北极海洋区域中至深海（>500 m）的Nd同位素组成相当均匀。在亚热带海洋区的两个站表现出类似的Nd同位素组成的配置文件，以前报道的。在两个亚热带站，在800-1000 m深度处出现最大的Nd（Nd）值（Nd = -3.4 ~-2.7），对应于北太平洋中层水（NPIW）。这意味着一个无处不在的分布的NPIW显示放射成因钕（Nd）值在北太平洋。在西太平洋的一个观测站观测到了次表层最小值，其深度接近200 m，表明北太平洋热带水（NPTW）具有非放射性Nd同位素信号。在5000 m附近，该站的Nd含量远低于中心站，表明南极底层水（AABW）在副热带西太平洋比在副热带中东太平洋更为突出。Nd同位素组成是研究大洋环流和北太平洋Nd地球化学循环的一种多功能示踪剂。进一步研究包括南太平洋在内的太平洋Nd同位素组成的分布，将有助于更好地阐明太平洋Nd的环流和地球化学循环。(C)2009爱思唯尔有限公司保留所有权利。
Three vertical profiles of seawater concentration and isotopic composition of Nd were determined for the western to central North Pacific Ocean.In the Subarctic oceanic region, at depths greater than 500 m, one vertical profile of Nd isotopic composition was indistinguishable from most previously reported profiles from here. The data indicate a rather homogeneous Nd isotopic composition in the subarctic oceanic region at middle to deep depths (>500 m). Two stations in the subtropical oceanic region exhibited similar Nd isotopic composition profiles to those previously reported. The maxima epsilon(Nd) values at depths of 800-1000 m (epsilon(Nd) = -3.4 to -2.7), which correspond to the North Pacific Intermediate Water (NPIW), are found at both subtropical stations. This implies a ubiquitous distribution of NPIW showing a radiogenic epsilon(Nd) value in the North Pacific. The sub-surface minimum at a depth of similar to 200 m, which indicates the penetration of the North Pacific Tropical Water (NPTW) with an unradiogenic Nd isotopic signal, was observed at one station in the western Pacific. This station had much lower epsilon(Nd) than the central station at depths around 5000 m, suggesting the greater prominence of Antarctic Bottom Water (AABW) in the western Subtropical Pacific than in the central to eastern Subtropical Pacific.Results of a model calculation assuming boundary exchange indicate that the Hawaiian Islands play an important role in supplying radiogenic Nd to the central Pacific, similar to some continental margins.We show that Nd isotopic composition is a versatile tracer for ocean Circulation and the geochemical cycle of Nd in the North Pacific. Further studies oil the distribution of Nd isotopic composition in the Pacific Ocean, including the Southern Pacific, will better elucidate the circulation and geochemical cycle of Nd in the Pacific. (C) 2009 Elsevier Ltd. All rights reserved.