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Authigenic Nd isotope record of North Pacific Intermediate Water formation and boundary exchange on the Bering Slope

Cited 15 time in wos
Cited 15 time in scopus
Title
Authigenic Nd isotope record of North Pacific Intermediate Water formation and boundary exchange on the Bering Slope
Other Titles
북태평양 중층수 형성과 베링 사면 경계 교환에 대한 자생성 네모디뮴 동위원소 기록
Authors
Kwangchul Jang
Han, Yeongcheol
Youngsook Huh
Keywords
AuthigenicBering SeaBrineNPIWNeodymiumSeesawVentilation
Issue Date
2017
Citation
Kwangchul Jang, Han, Yeongcheol, Youngsook Huh. 2017. "Authigenic Nd isotope record of North Pacific Intermediate Water formation and boundary exchange on the Bering Slope". QUATERNARY SCIENCE REVIEWS, 156(1): 150-163.
Abstract
The Bering Sea is a potential location for the formation of the North Pacific Intermediate Water (NPIW), which drives the global ocean circulation as a counterpart to the North Atlantic Deep Water (NADW). To evaluate the NPIW-NADW seesaw hypothesis, we reconstructed the long-term variation of the bottom water Nd isotopic composition at site U1345 on the Bering Slope by extracting authigenic Fe-Mn oxyhydroxide from bulk sediments. We examined six different extractions in order to ensure that authentic seawater composition is recovered. For Bering Slope sediments whose typical carbonate content is less than 5% (average 2%), the most reliable results are obtained if the decarbonation step is omitted and a low reagent-to-sediment ratio is adopted. The reconstructed authigenic εNd record for the last 520 kyr exhibits large temporal variations depending on whether the NPIW formation or the boundary exchange process is dominant. Periods of radiogenic εNd can be attributed to NPIW formation triggered by brine rejection, as evidenced by the difference in d18O of benthic foraminifera between sites (Dd18Obf), high % sea-ice related diatoms, and low abundance of Bulimina aff. Exilis (low-oxygen deep fauna). Diminished supply of unradiogenic Nd from boundary exchange seems to intensify these radiogenic peaks. On the other hand, the unradiogenic εNd intervals can be attributed to stagnant bottom water conditions, as can be deduced from the Dd18Obf values, low % sea-ice related diatoms, abundant B. aff. Exilis, and laminations. When there is no NPIW formation, the continental margin sediments are exposed to boundary exchange for a longer period of time, leading to release of unradiogenic Nd. The mid-MIS 6 and mid-MIS 5 are exceptions in that NPIW formation occurred yet the εNd compositions are unradiogenic. NPIW formation and cold climate (closed Bering Strait) are not always correlated. Comparison against εNd records of the South Atlantic suggests only an ambiguous NPIW-NADW seesaw for the last 200 kyr.
URI
https://repository.kopri.re.kr/handle/201206/7517
DOI
http://dx.doi.org/10.1016/j.quascirev.2016.11.032
Type
Article
Indexed
SCI
Appears in Collections  
2014-2016, Characteristics of gas hydrate and reconstruction of paleo-environment changes in the western Arctic (14-16) / Nam, Seung-Il (PE14062; PE15062; PE16062)
2014-2016, Investigation of Climate Change Mechanism by Observation and Simulation of Polar Climate for The Past and Present (14-16) / Kim, Seong-Joong (PE14010; PE15010; PE16010)
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