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Assessment of C, N and Si isotopes as tracers of past ocean nutrient and carbon cycling
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  • Jesse Farmer,
  • Jennifer Hertzberg,
  • Damien Cardinal,
  • Susanne Fietz,
  • Katharine Hendry,
  • Sam Jaccard,
  • Adina Paytan,
  • Patrick Rafter,
  • Haojia Ren,
  • Christopher Somes,
  • Jill Sutton
Jesse Farmer
Department of Geosciences, Princeton University, Department of Geosciences, Princeton University

Corresponding Author:[email protected]

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Jennifer Hertzberg
Old Dominion University, Old Dominion University
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Damien Cardinal
LOCEAN (UMR7159), Sorbonne Université, IRD, CNRS, MNHN, LOCEAN (UMR7159), Sorbonne Université, IRD, CNRS, MNHN
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Susanne Fietz
Stellenbosch University, Stellenbosch University
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Katharine Hendry
University of Bristol,University of Bristol, University of Bristol,University of Bristol
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Sam Jaccard
University of Lausanne, University of Lausanne
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Adina Paytan
University of California, Santa Cruz, University of California, Santa Cruz
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Patrick Rafter
University of California Irvine, University of California Irvine
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Haojia Ren
National Taiwan University, National Taiwan University
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Christopher Somes
GEOMAR Helmholtz Centre for Ocean Research Kiel, GEOMAR Helmholtz Centre for Ocean Research Kiel
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Jill Sutton
Univ Brest, CNRS, IRD, Ifremer, Institut Universitaire Européen de la Mer, LEMAR, Univ Brest, CNRS, IRD, Ifremer, Institut Universitaire Européen de la Mer, LEMAR
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Biological productivity in the ocean directly influences the partitioning of carbon between the atmosphere and ocean interior. Through this carbon cycle feedback, changing ocean productivity has long been hypothesized as a key pathway for modulating past atmospheric carbon dioxide levels and hence global climate. Because phytoplankton preferentially assimilate the light isotopes of carbon and the major nutrients nitrate and silicic acid, stable isotopes of carbon (C), nitrogen (N), and silicon (Si) in seawater and marine sediments can inform on ocean carbon and nutrient cycling, and by extension the relationship with biological productivity and global climate. Here we compile water column C, N, and Si stable isotopes from GEOTRACES-era data in four key ocean regions to review geochemical proxies of oceanic carbon and nutrient cycling based on the C, N, and Si isotopic composition of marine sediments. External sources and sinks as well as internal cycling (including assimilation, particulate matter export, and regeneration) are discussed as likely drivers of observed C, N, and Si isotope distributions in the ocean. The potential for C, N, and Si isotope measurements in sedimentary archives to record aspects of past ocean C and nutrient cycling is evaluated, along with key uncertainties and limitations associated with each proxy. Constraints on ocean C and nutrient cycling during late Quaternary glacial-interglacial cycles and over the Cenozoic are examined. This review highlights opportunities for future research using multielement stable isotope proxy applications and emphasizes the importance of such applications to reconstructing past changes in the oceans and climate system.