A reevaluation of the magnitude and impacts of anthropogenic atmospheric nitrogen inputs on the ocean
| Autor: | Robert A. Duce, Katja Fennel, Maria Kanakidou, Mitsuo Uematsu, Manmohan Sarin, Alex R. Baker, G. S. Okin, Jonathan Sharples, Kitack Lee, Arvind Singh, F. J. Dentener, Tim Jickells, Douglas G. Capone, Julie LaRoche, Andreas Oschlies, Parvadha Suntharalingam, J. K. Moore, Sybil P. Seitzinger, Lauren Zamora, Katye E. Altieri, Peter S. Liss, Jack J. Middelburg, Erik T. Buitenhuis |
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| Rok vydání: | 2017 |
| Předmět: |
0106 biological sciences
Atmospheric Science Denitrification 010504 meteorology & atmospheric sciences Climate change chemistry.chemical_element Carbon sequestration 01 natural sciences Environmental Chemistry 14. Life underwater Nitrogen cycle 0105 earth and related environmental sciences General Environmental Science Global and Planetary Change geography geography.geographical_feature_category Continental shelf 010604 marine biology & hydrobiology Biogeochemistry 15. Life on land Nitrogen Human impact on the nitrogen cycle Oceanography chemistry 13. Climate action Environmental science |
| Zdroj: | Global Biogeochemical Cycles. |
| ISSN: | 0886-6236 |
| Popis: | We report a new synthesis of best estimates of the inputs of fixed nitrogen to the world ocean via atmospheric deposition and compare this to fluvial inputs and dinitrogen fixation. We evaluate the scale of human perturbation of these fluxes. Fluvial inputs dominate inputs to the continental shelf, and we estimate that about 75% of this fluvial nitrogen escapes from the shelf to the open ocean. Biological dinitrogen fixation is the main external source of nitrogen to the open ocean, i.e., beyond the continental shelf. Atmospheric deposition is the primary mechanism by which land-based nitrogen inputs, and hence human perturbations of the nitrogen cycle, reach the open ocean. We estimate that anthropogenic inputs are currently leading to an increase in overall ocean carbon sequestration of ~0.4% (equivalent to an uptake of 0.15 Pg C yr−1 and less than the Duce et al. (2008) estimate). The resulting reduction in climate change forcing from this ocean CO2 uptake is offset to a small extent by an increase in ocean N2O emissions. We identify four important feedbacks in the ocean atmosphere nitrogen system that need to be better quantified to improve our understanding of the perturbation of ocean biogeochemistry by atmospheric nitrogen inputs. These feedbacks are recycling of (1) ammonia and (2) organic nitrogen from the ocean to the atmosphere and back, (3) the suppression of nitrogen fixation by increased nitrogen concentrations in surface waters from atmospheric deposition, and (4) increased loss of nitrogen from the ocean by denitrification due to increased productivity stimulated by atmospheric inputs. |
| Databáze: | OpenAIRE |
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