MEPS 371:301-303 (2008)  -  DOI: https://doi.org/10.3354/meps07772

COMMENT
Widespread implementation of controlled upwelling in the North Pacific Subtropical Gyre would counteract diazotrophic N2 fixation

Katja Fennel*

Department of Oceanography, Dalhousie University, Halifax, Nova Scotia, Canada

ABSTRACT: Karl & Letelier (2008; Mar Ecol Prog Ser 364:257–268) examined the stimulation of diazotrophic N2 fixation by controlled upwelling of deep-water nutrients as a potential carbon sequestration strategy in low-nutrient, low-chlorophyll regions such as the North Pacific Subtropical Gyre. They did not examine the effect of buoyancy on vertical stratification. Since seawater upwelled from depth is colder and saltier, and therefore denser than surface water, it would have to be diluted sufficiently to prevent its convective sinking. This dilution would lead to a decrease in vertical stratification, which could counteract N2 fixation, as diazotrophs bloom only under well-stratified conditions. A back-of-the-envelope calculation of the effect of large-scale controlled upwelling on upper ocean stratification shows that controlled upwelling is unlikely to scale up and serve as a climate stabilization wedge as defined by Pacala & Socolow (2004; Science 305:968–972), i.e. it would not sequester 1 Gt C yr–1 over 30 yr.


KEY WORDS: Carbon sequestration · Nitrogen fixation · LNLC · Mixed-layer depth · NSPG · Controlled upwelling · Climate stabilisation wedge


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Cite this article as: Fennel K (2008) Widespread implementation of controlled upwelling in the North Pacific Subtropical Gyre would counteract diazotrophic N2 fixation. Mar Ecol Prog Ser 371:301-303. https://doi.org/10.3354/meps07772

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