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- Title
Marine denitrification rates determined from a global 3-D inverse model.
- Authors
DeVries, T.; Deutsch, C.; Rafter, P. A.; Primeau, F.
- Abstract
A major impediment to understanding long-term changes in the marine nitrogen (N) cycle is the persistent uncertainty about the rates, distribution, and sensitivity of its largest fluxes in the modern ocean. We use a global ocean circulation model to obtain the first 3-D estimate of marine denitrification rates that is maximally consistent with available observations of nitrate deficits and the nitrogen isotopic ratio of oceanic nitrate. We find a global rate of marine denitrification in suboxic waters and sediments of 120-240 TgNyr-1, which is lower than many other recent estimates. The difference stems from the ability to represent the 3-D spatial structure of suboxic zones, where denitrification rates of 50-77 TgNyr-1 result in up to 50% depletion of nitrate. This depletion reduces the effect of local isotopic enrichment on the rest of the ocean, allowing the N isotope ratio of oceanic nitrate to be achieved with a sedimentary denitrification rate about 1.3-2.3 times that of suboxic zones. This balance of N losses between sediments and suboxic zones is shown to obey a simple relationship between isotope frac-tionation and the degree of nitrate consumption in the core of the suboxic zones. The global denitrification rates derived here suggest that the marine nitrogen budget is likely close to balanced.
- Subjects
DENITRIFICATION; NITROGEN content of seawater; UNCERTAINTY (Information theory); SENSITIVITY analysis; MARINE sediments; OCEAN circulation; DOSE fractionation; MARINE pollution
- Publication
Biogeosciences, 2013, Vol 10, Issue 4, p2481
- ISSN
1726-4170
- Publication type
Article
- DOI
10.5194/bg-10-2481-2013