A reevaluation of the magnitude and impacts of anthropogenic atmospheric nitrogen inputs on the ocean
A reevaluation of the magnitude and impacts of anthropogenic atmospheric nitrogen inputs on the ocean
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DOI：
10.1002/2016gb005586
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发表时间：
2017-02-01
影响因子：
5.2
通讯作者：
Zamora, L. M.
中科院分区：
文献类型：
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作者：
Jickells, T. D.;Buitenhuis, E.;Zamora, L. M.
我们报告了一个新的合成的最佳估计的输入固定氮通过大气沉积到世界海洋，并比较这河流输入和固氮。我们评估这些通量的人类扰动的规模。河流输入占主导地位的输入大陆架，我们估计，约75%的河流氮从大陆架逃逸到公海。生物固氮是开放海洋氮的主要外部来源，即，在大陆架之外。大气沉积是陆地氮输入以及人类对氮循环的扰动到达公海的主要机制。我们估计，目前人为输入导致海洋碳固存总量增加约0.4%（相当于吸收0.15 Pg Cyr（-1），低于Duce等人（2008）的估计）。海洋吸收CO2所导致的气候变化作用力的减少在很小程度上被海洋N2 O排放量的增加所抵消。我们确定了四个重要的反馈，在海洋大气氮系统，需要更好地量化，以提高我们的理解，大气氮输入的海洋地球化学扰动。这些反馈是（1）氨和（2）有机氮从海洋到大气再循环，（3）通过大气沉积增加表层沃茨中的氮浓度而抑制固氮作用，以及（4）由于大气输入刺激的生产力增加而通过反硝化作用增加海洋中的氮损失。
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 similar to 0.4% (equivalent to an uptake of 0.15 Pg Cyr(-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.