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  Ice age‐Holocene similarity of foraminifera‐bound nitrogen isotope ratios in the eastern equatorial Pacific

Studer, A. S., Mekik, F., Ren, H., Hain, M. P., Oleynik, S., Martinez-Garcia, A., et al. (2021). Ice age‐Holocene similarity of foraminifera‐bound nitrogen isotope ratios in the eastern equatorial Pacific. Paleoceanography and paleoclimatology, 36: e2020PA004063. doi:10.1029/2020PA004063.

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 Creators:
Studer, Anja S.1, Author              
Mekik, Figen, Author
Ren, Haojia, Author
Hain, Mathis P., Author
Oleynik, Sergey, Author
Martinez-Garcia, Alfredo1, Author              
Haug, Gerald H.1, Author              
Sigman, Daniel M., Author
Affiliations:
1Climate Geochemistry, Max Planck Institute for Chemistry, Max Planck Society, ou_2237635              

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 Abstract: Bulk sediment δ15N records from the eastern tropical Pacific (ETP) extending back to the last ice age most often show low glacial δ15N, then a deglacial δ15N maximum, followed by a gradual decline to a late Holocene δ15N that is typically higher than that of the Last Glacial Maximum (LGM). The lower δ15N of the LGM has been interpreted to reflect an ice age reduction in water column denitrification. We report foraminifera shell‐bound nitrogen isotope (FB‐δ15N) measurements for the two species Neogloboquadrina dutertrei and Neogloboquadrina incompta over the last 35 ka in two sediment cores from the eastern equatorial Pacific (EEP), both of which have the typical LGM‐to‐Holocene increase in bulk sediment δ15N. FB‐δ15N contrasts with bulk sediment δ15N by not indicating a lower δ15N during the LGM. Instead, the FB‐δ15N records are dominated by a deglacial δ15N maximum, with comparable LGM and Holocene values. The lower LGM δ15N of the bulk sediment records may be an artifact, possibly related to greater exogenous N inputs and/or weaker sedimentary diagenesis during the LGM. The new data raise the possibility that the previously inferred glacial reduction in ETP water column denitrification was incorrect. A review of reconstructed ice age conditions and geochemical box model output provides mechanistic support for this possibility. However, equatorial ocean circulation and nitrate‐rich surface water overlying both core sites allow for other possible interpretations, calling for replication at non‐equatorial ETP sites.

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Language(s): eng - English
 Dates: 2021-04-22
 Publication Status: Published online
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 Table of Contents: -
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 Identifiers: DOI: 10.1029/2020PA004063
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Title: Paleoceanography and paleoclimatology
Source Genre: Journal
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Publ. Info: Hoboken, NJ : Wiley
Pages: - Volume / Issue: 36 Sequence Number: e2020PA004063 Start / End Page: - Identifier: ISSN: 1944-9186
CoNE: https://pure.mpg.de/cone/journals/resource/1944-9186