Sedimentary records of nitrogen isotope in the western tropical Pacific linked to the eastern tropical Pacific denitrification during the last deglacial time
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The influence of past variations in water column denitrification (WCD) in the eastern tropical Pacific (ETP) on the western tropical Pacific (WTP) remains ambiguous, due to the deficiency of enough down-core records of nitrogen isotope (δ15N) in the WTP. In this study, sedimentary δ15N record down a core from the northern WTP is investigated to revisit this issue. After elucidating the potential presence of multiple forms of N by analyzing bulk parameters and the potential occurrence of alteration by examining amino acids, the bulk sedimentary δ15N can be accepted as an available indicator of nitrate δ15N. Further, a comprehensive comparison of δ15N records in the North Pacific reveals largely similar variations from the last glacial maximum to early Holocene, suggesting a common feature of WCD signals associated with basin-scale processes, likely as a consequence of basin-wide ocean circulations. Our result suggests that the signals of local N2 fixation in the western Pacific marginal seas would have been constrained by a synchronous glacial-interglacial change of the source WCD signals.
KeywordsNitrogen isotope Bulk parameters Amino acids Western tropical Pacific
We thank the crew of the RV KEXUE for their help during the cruises. Special thanks go to the editors and reviewer for their thoughtful and constructive comments that greatly improved the clarity and quality of the manuscript.
This work was funded by The Senior User Project of RV KEXUE (No. KEXUE2018G06), the State Key R&D project (No. 2016YFA0601104), K.C. Wong Education Foundation (No. GJTD-2018-13), the National Natural Science Foundation of China (Nos. 41706059 and 41877295), the Strategic Priority Research Program of the Chinese Academy of Sciences (No. XDA11030103), Science and Technology Program of Guangzhou, China (No. 201707010219), and Science and Technology Basic Resources Investigation Program of China (No. 2017FY201403).
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