Preprints
https://doi.org/10.5194/egusphere-2024-123
https://doi.org/10.5194/egusphere-2024-123
18 Jan 2024
 | 18 Jan 2024

Global impact of benthic denitrification on marine N2 fixation and primary production simulated by a variable-stoichiometry Earth system model

Na Li, Christopher J. Somes, Angela Landolfi, Chia-Te Chien, Markus Pahlow, and Andreas Oschlies

Abstract. Nitrogen (N) is a crucial limiting nutrient for phytoplankton growth in the ocean. The main source of bioavailable N in the ocean is delivered by N2-fixing diazotrophs in the surface layer. Since field observation of N2 fixation are spatially and temporally sparse, the fundamental processes and mechanisms controlling N2 fixation are not well understood and constrained. Here, we implement benthic denitrification in an Earth System Model of intermediate complexity (UVic-ESCM 2.9) coupled to an optimality-based plankton ecosystem model (OPEM v1.1). Benthic denitrification occurs mostly in coastal upwelling regions and on shallow continental shelves, and is the largest N-loss process in the global ocean. We calibrate our model against three different combinations of observed Chl, NO3-, PO43-, O2 and N* = NO3- −16PO43- +2.9. The inclusion of N* provides a powerful constraint on biogeochemical model behavior. Our new model version including benthic denitrification simulates higher global rates of N2 fixation with a more realistic distribution extending to higher latitudes that are supported by independent estimates based on geochemical data. Oxygen deficient zone volume and water column denitrification rates are reduced in the new version, indicating that including benthic denitrification may improve global biogeochemical models that commonly overestimate anoxic zones. With the improved representation of the ocean N cycle, our new model configuration also yields better global net primary production (NPP) when compared to the independent datasets not included in the calibration. Benthic denitrification plays an important role shaping N2 fixation and NPP throughout the global ocean in our model, and should be considered when evaluating and predicting their response to environmental change.

Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this preprint. The responsibility to include appropriate place names lies with the authors.
Na Li, Christopher J. Somes, Angela Landolfi, Chia-Te Chien, Markus Pahlow, and Andreas Oschlies

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2024-123', Anonymous Referee #1, 04 May 2024
  • RC2: 'Comment on egusphere-2024-123', Anonymous Referee #2, 05 Jun 2024
Na Li, Christopher J. Somes, Angela Landolfi, Chia-Te Chien, Markus Pahlow, and Andreas Oschlies
Na Li, Christopher J. Somes, Angela Landolfi, Chia-Te Chien, Markus Pahlow, and Andreas Oschlies

Viewed

Total article views: 339 (including HTML, PDF, and XML)
HTML PDF XML Total BibTeX EndNote
240 82 17 339 9 8
  • HTML: 240
  • PDF: 82
  • XML: 17
  • Total: 339
  • BibTeX: 9
  • EndNote: 8
Views and downloads (calculated since 18 Jan 2024)
Cumulative views and downloads (calculated since 18 Jan 2024)

Viewed (geographical distribution)

Total article views: 332 (including HTML, PDF, and XML) Thereof 332 with geography defined and 0 with unknown origin.
Country # Views %
  • 1
1
 
 
 
 
Latest update: 12 Jun 2024
Download
Short summary
N is an important nutrient that limits phytoplankton growth in large parts of the ocean. The amount of oceanic N is governed by the balance of N2 fixation and denitrification. Here we incorporate benthic denitrification in an Earth system model with variable stoichiometry. Our model compares better to the observed surface nutrient distributions, marine N2 fixation and primary production. Benthic denitrification plays an important role in marine N and C cycling, and hence the global climate.