07 Feb 2022
07 Feb 2022
Status: this preprint is currently under review for the journal BG.

Quantifying biological carbon pump pathways with a data-constrained mechanistic model ensemble approach

Michael R. Stukel1,2, Moira Décima3, and Michael Landry3 Michael R. Stukel et al.
  • 1Dept. of Earth, Ocean, and Atmospheric Science, Florida State University, Tallahassee, FL
  • 2Center for Ocean-Atmospheric Prediction Studies, Florida State University, Tallahassee, FL
  • 3Scripps Institution of Oceanography, University of California San Diego, San Diego, CA

Abstract. The ability to constrain the mechanisms that transport organic carbon into the deep ocean is complicated by the multiple physical, chemical, and ecological processes that intersect to create, transform, and transport particles in the ocean. In this manuscript we develop and parameterize a data-assimilative model of the multiple pathways of the biological carbon pump (NEMUROBCP). The mechanistic model is designed to represent sinking particle flux, active transport by vertically migrating zooplankton, and passive transport by subduction and vertical mixing, while also explicitly representing multiple biological and chemical properties measured directly in the field (including nutrients, phytoplankton and zooplankton taxa, carbon dioxide and oxygen, nitrogen isotopes, and 234Thorium). Using 30 different data types (including standing stock and rate measurements related to nutrients, phytoplankton, zooplankton, and non-living organic matter) from Lagrangian experiments conducted on 11 cruises from four ocean regions, we conduct an objective statistical parameterization of the model and generate one million different potential parameter sets that are used for ensemble model simulations. The model simulates in situ parameters that were assimilated (net primary production and gravitational particle flux) and parameters that were withheld (234Thorium and nitrogen isotopes) with reasonable accuracy. Model results show that gravitational flux of sinking particles and vertical mixing of organic matter from the surface ocean are more important biological pump pathways than active transport by vertically migrating zooplankton. However, these processes are regionally variable, with sinking particles most important in oligotrophic areas of the Gulf of Mexico and California, sinking particles and vertical mixing roughly equivalent in productive regions of the CCE and the subtropical front in the Southern Ocean, and active transport an important contributor in the Eastern Tropical Pacific. We further find that mortality at depth is an important component of active transport when mesozooplankton biomasses are high, but that it is negligible in regions with low mesozooplankton biomass. Our results also highlight the high degree of uncertainty, particularly amongst mesozooplankton functional groups, that is derived from uncertainty in model parameters, with important implications for results that rely on non-ensemble model outputs. We also discuss the implications of our results for other data assimilation approaches.

Michael R. Stukel et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on bg-2022-7', Vassilios Vervatis, 17 Mar 2022
    • AC1: 'Reply on RC1', Mike Stukel, 22 Apr 2022
  • RC2: 'Comment on bg-2022-7', Anonymous Referee #2, 10 Apr 2022
    • AC2: 'Reply on RC2', Mike Stukel, 22 Apr 2022

Michael R. Stukel et al.

Michael R. Stukel et al.


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Short summary
The biological carbon pump (BCP) transports carbon into the deep ocean leading to long-term marine carbon sequestration. It is driven by many physical, chemical and ecological processes. We developed a model of the BCP constrained using data from 11 cruises in 4 different ocean regions. Our results show that sinking particles and vertical mixing are important than transport mediated by vertically migrating zooplankton. They also highlight the uncertainty in current estimates of the BCP.