Assessment of C, N, and Si Isotopes as tracers of past ocean nutrient and carbon cycling
Date
2021
Journal Title
Journal ISSN
Volume Title
Publisher
John Wiley & Sons, Inc.
Abstract
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.
Description
CITATION: Farmer, J. R., Hertzberg, J. E., Cardinal, D., Fietz, S., Hendry, K., Jaccard, S. L., et al. (2021). Assessment of C,
N, and Si isotopes as tracers of past ocean nutrient and carbon cycling. Global Biogeochemical Cycles,
35, e2020GB006775. doi.10.1029/2020GB006775
The original publication is available at: wiley.com
The original publication is available at: wiley.com
Keywords
Stable isotope tracers, Ocean nutrient, Carbon cycle (Biogeochemistry), Biological productivity, Atmospheric carbon dioxide -- Climatic factors, Phytoplankton -- Nutrition