Deep circulation changes in the central South Atlantic during the past 145 kyrs reflected in a combined231Pa/230Th, Neodymium isotope and benthic δ13C record
Deep circulation changes in the central South Atlantic during the past 145 kyrs reflected in a combined231Pa/230Th, Neodymium isotope and benthic δ13C record
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过去 145 kyrs 期间南大西洋中部深部环流变化反映在 231Pa/230Th、钕同位素和底栖 δ13C 组合记录中
DOI：
10.1016/j.epsl.2015.03.004
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发表时间：
2015
影响因子：
5.3
通讯作者：
T. Bickert
中科院分区：
文献类型：
--
作者：
L. Jonkers;R. Zahn;Alexander L. Thomas;G. Henderson;W. Abouchami;R. Francois;P. Masqué;I. Hall;T. Bickert
前人的工作表明，南大西洋沉积物的冰期比全新世231Pa230Th要低，这归因于大西洋深水流向的转换。然而，关于两个过程--环流和清扫--在多大程度上决定了沉积的231Pa230Th，存在争议，这使得这种解释存在争议。在这里，我们使用145-KYR古循环代用记录来解决这个问题。在南大西洋副热带环流的一个沉积物柱样中测量了底栖有孔虫δC13、钕同位素(ε-ND)和沉积231Pa230Th。该站点在很大程度上排除了当地生产力变化对231Pa230Th记录的影响。测量的231Pa230Th介于冰期的∼0.041和间冰期的∼0.055之间，一直低于生产比率，表明在整个记录期间从南大西洋中部出口231Pa.下冰期231Pa/230Th在区域上是一致的，表明盆地尺度的海洋过程导致了这一下降。反过来，低辐射成因的εND和较低的底栖生物δC13证实了冰期大西洋南方分量水影响增加的经典图景，并指出环流控制了观测到的231Pa230Th的下降，而不是局部生产力的变化。我们认为，与水团分布的这种变化有关，231Pa的主要汇在间冰期期间从南大西洋和/或南大洋边缘转移到冰期期间的北大西洋。实际上，冰期期间北大西洋深处231Pa230 Th的升高支持了这种通过SCW向北输送231Pa.
Previous work showed that South Atlantic sediments have lower glacial than Holocene 231 Pa/230 Th, which was attributed to a switch in the flow direction of Atlantic deep-water. Debate exists, however as to the degree to which two processes–circulation and scavenging–determine sedimentary 231 Pa/230 Th, making this interpretation contentious. Here we address this issue using 145-kyr records of paleocirculation proxies. Benthic foraminiferal δ C 13, neodymium isotopes (ε Nd) and sedimentary 231 Pa/230 Th were all measured in a single sediment core from the South Atlantic subtropical gyre. This site largely excludes the influence of local productivity changes on 231 Pa/230 Th records. Measured 231 Pa/230 Th ranges between∼ 0.041 during glacials and∼ 0.055 during interglacial periods and is consistently lower than the production ratio, indicating export of 231 Pa from the central South Atlantic for the entire duration of the record. The lower glacial 231 Pa/230 Th is regionally consistent, suggesting that basin-scale oceanographic processes cause the decrease. In turn, less radiogenic ε Nd and lower benthic δ C 13 confirm the classical picture of an increase in Southern Component Water (SCW) influence in the Atlantic during glacial periods and point to a circulation control on the observed 231 Pa/230 Th decrease rather than a local productivity change. We suggest that associated with this change in water mass distribution the dominant sink for 231 Pa shifted from the margins of the South Atlantic and/or the Southern Ocean during interglacials, to the North Atlantic during glacial periods. Indeed, elevated 231 Pa/230 Th in the deep North Atlantic during glacials supports this mechanism of northward transport of 231 Pa by SCW.
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影响因子：
5.3
作者：
T. Stichel;M. Frank;J. Rickli;B. Haley
通讯作者：
T. Stichel;M. Frank;J. Rickli;B. Haley
冰川大西洋经向翻转环流的强度和几何形状
影响因子：
18.3
作者：
Lippold;Y. Luo;R. Francois;S. Allen;J. Gherardi;S. Pichat;B. Hickey;H. Schulz
通讯作者：
H. Schulz
影响因子：
5.3
作者：
Deng, Feifei;Thomas, Alex L.;Henderson, Gideon M.
通讯作者：
Henderson, Gideon M.
影响因子：
5.8
作者：
Foster, Gavin L.;Vance, Derek;Prytulak, Julie
通讯作者：
Prytulak, Julie
影响因子：
64.8
作者：
Boehm, E.;Lippold, J.;Deininger, M.
通讯作者：
Deininger, M.