Shallow particulate organic carbon regeneration in the South Pacific Ocean

Frank J. Pavia, Robert F. Anderson, Phoebe J. Lam, B. B. Cael, Sebastian M. Vivancos, Martin Q. Fleisher, Yanbin Lu, Pu Zhang, Hai Cheng, Larry Edwards

Research output: Contribution to journalArticlepeer-review

14 Scopus citations

Abstract

Particulate organic carbon (POC) produced in the surface ocean sinks through the water column and is respired at depth, acting as a primary vector sequestering carbon in the abyssal ocean. Atmospheric carbon dioxide levels are sensitive to the length (depth) scale over which respiration converts POC back to inorganic carbon, because shallower waters exchange with the atmosphere more rapidly than deeper ones. However, estimates of this carbon regeneration length scale and its spatiotemporal variability are limited, hindering the ability to characterize its sensitivity to environmental conditions. Here, we present a zonal section of POC fluxes at high vertical and spatial resolution from the GEOTRACES GP16 transect in the eastern tropical South Pacific, based on normalization to the radiogenic thorium isotope 230Th. We find shallower carbon regeneration length scales than previous estimates for the oligotrophic South Pacific gyre, indicating less efficient carbon transfer to the deep ocean. Carbon regeneration is strongly inhibited within suboxic waters near the Peru coast. Canonical Martin curve power laws inadequately capture POC flux profiles at suboxic stations. We instead fit these profiles using an exponential function with flux preserved at depth, finding shallow regeneration but high POC sequestration below 1,000 m. Both regeneration length scales and POC flux at depth closely track the depths at which oxygen concentrations approach zero. Our findings imply that climate warming will result in reduced ocean carbon storage due to expanding oligotrophic gyres, but opposing effects on ocean carbon storage from expanding suboxic waters will require modeling and future work to disentangle.

Original languageEnglish (US)
Pages (from-to)9753-9758
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume116
Issue number20
DOIs
StatePublished - May 14 2019

Bibliographical note

Funding Information:
We thank the captain and crew of the Research Vessel Thomas G. Thompson during the TN303 cruise. The pump team led by Dan Ohnemus was responsible for the collection of the particulate samples used in this study. We thank Kassandra Costa for comments on an early draft of the paper, as well as two anonymous reviewers and the handling editor for constructive feedback. This work was funded by US National Science Foundation Awards OCE-1233688 (to R.F.A.), OCE-1233903 (to R.L.E.), and OCE-1518110 (to P.J.L.), and by the NSF Graduate Research Fellowship DGE-16-44869 (to F.J.P.).

Funding Information:
Foundation Awards OCE-1233688 (to R.F.A.), OCE-1233903 (to R.L.E.), and OCE-1518110 (to P.J.L.), and by the NSF Graduate Research Fellowship DGE-16-44869 (to F.J.P.).

Funding Information:
used in this study. We thank Kassandra Costa for comments on an early draft of the paper, as well as two anonymous reviewers and the handling editor for constructive feedback. This work was funded by US National Science

Publisher Copyright:
© 2019 National Academy of Sciences. All rights reserved.

Keywords

  • Biological pump
  • GEOTRACES
  • Ocean carbon storage
  • Oxygen-deficient zones
  • Thorium

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