Preprints
https://doi.org/10.5194/bg-2020-479
https://doi.org/10.5194/bg-2020-479

  04 Jan 2021

04 Jan 2021

Review status: a revised version of this preprint was accepted for the journal BG and is expected to appear here in due course.

Sensitivity of 21st-century projected ocean new production changes to idealized biogeochemical model structure

Genevieve Jay Brett1, Daniel B. Whitt2, Matthew C. Long2, Frank Bryan2, Kate Feloy1, and Kelvin J. Richards1 Genevieve Jay Brett et al.
  • 1University of Hawaii Manoa
  • 2National Center for Atmospheric Research

Abstract. While there is agreement that global warming over the 21st century is likely to influence the biological pump, Earth system models (ESM) display significant divergence in their projections of future new production. This paper quantifies and interprets the sensitivity of projected changes in new production in an idealized global ocean-biogeochemistry model. The model includes two tracers that explicitly represent nutrient transport, light- and nutrient-limited nutrient uptake by the ecosystem (new production), and export via sinking organic particles. Globally, new production declines with warming due to reduced surface nutrient availability, as expected. However, the magnitude, seasonality, and underlying dynamics of the nutrient uptake are sensitive to the light and nutrient dependencies of uptake, which we summarize in terms of a single biological timescale that is a linear combination of the partial derivatives of production with respect to light and nutrients. Although the relationships are non-linear, this biological timescale is correlated with several measures of biogeochemical function: shorter timescales are associated with greater global annual new production and higher nutrient utilization. Shorter timescales are also associated with greater declines in global new production in a warmer climate and greater sensitivity to changes in nutrient than light. Future work is needed to characterize more complex ocean biogeochemical models in terms of similar timescale generalities to examine their climate change implications.

Genevieve Jay Brett et al.

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on bg-2020-479', Anonymous Referee #1, 28 Jan 2021
    • AC1: 'Reply on RC1', Genevieve Brett, 05 Feb 2021
    • AC2: 'Final reply on RC1', Genevieve Brett, 09 Mar 2021
  • RC2: 'Comment on bg-2020-479', Anonymous Referee #2, 02 Feb 2021
    • AC3: 'Reply on RC2', Genevieve Brett, 10 Mar 2021

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on bg-2020-479', Anonymous Referee #1, 28 Jan 2021
    • AC1: 'Reply on RC1', Genevieve Brett, 05 Feb 2021
    • AC2: 'Final reply on RC1', Genevieve Brett, 09 Mar 2021
  • RC2: 'Comment on bg-2020-479', Anonymous Referee #2, 02 Feb 2021
    • AC3: 'Reply on RC2', Genevieve Brett, 10 Mar 2021

Genevieve Jay Brett et al.

Data sets

Data, Sensitivity of 21st-century projected ocean new production changes to idealized biogeochemical model structure Genevieve Jay Brett https://doi.org/10.5281/zenodo.4361701

Model code and software

gjayb/CESMtracer v1.0 (Version v1.0) Genevieve Jay Brett https://doi.org/10.5281/zenodo.4361705

Genevieve Jay Brett et al.

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Short summary
We quantify one form of uncertainty in modeled 21st-century changes in phytoplankton growth. The supply of nutrients from deep to surface waters decreases in the warmer future ocean, but the effect on phytoplankton growth also depends on changes in available light, how much light and nutrient the plankton need, and how fast they can grow. These phytoplankton properties can be summarized as a biological timescale: when it is short, future growth decreases twice as much as when it is long.
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