Simulated 21st century's increase in oceanic suboxia by CO(2)-enhanced biotic carbon export

TitleSimulated 21st century's increase in oceanic suboxia by CO(2)-enhanced biotic carbon export
Publication TypeJournal Article
Year of Publication2008
AuthorsOschlies, A., K. G. Schulz, U. Riebesell, and A. Schmittner
JournalGlobal Biogeochemical Cycles
Volume22
Date PublishedNov 11
ISBN Number0886-6236
Accession NumberISI:000260991700001
Keywordsarabian sea, atmospheric co2, climate model, cycle, denitrification, fixation, high co2 ocean, nitrogen, ratios
Abstract

The primary impacts of anthropogenic CO(2) emissions on marine biogeochemical cycles predicted so far include ocean acidification, global warming induced shifts in biogeographical provinces, and a possible negative feedback on atmospheric CO(2) levels by CO(2)-fertilized biological production. Here we report a new potentially significant impact on the oxygen-minimum zones of the tropical oceans. Using a model of global climate, ocean circulation, and biogeochemical cycling, we extrapolate mesocosm-derived experimental findings of a pCO(2)-sensitive increase in biotic carbon-to-nitrogen drawdown to the global ocean. For a simulation run from the onset of the industrial revolution until A.D. 2100 under a "business-as-usual'' scenario for anthropogenic CO(2) emissions, our model predicts a negative feedback on atmospheric CO(2) levels, which amounts to 34 Gt C by the end of this century. While this represents a small alteration of the anthropogenic perturbation of the carbon cycle, the model results reveal a dramatic 50% increase in the suboxic water volume by the end of this century in response to the respiration of excess organic carbon formed at higher CO(2) levels. This is a significant expansion of the marine "dead zones'' with severe implications not only for all higher life forms but also for oxygen-sensitive nutrient recycling and, hence, for oceanic nutrient inventories.

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