Denitrification and N2 fixation in the Pacific Ocean
Denitrification and N2 fixation in the Pacific Ocean
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DOI：
10.1029/2000gb001291
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发表时间：
2001-06-01
影响因子：
5.2
通讯作者：
Ganachaud, A
中科院分区：
文献类型：
--
作者：
Deutsch, C;Gruber, N;Ganachaud, A
我们根据最近完成的世界海洋环流实验（WOCE）的营养场建立了太平洋的固定氮预算。预算包括水体和沉积物中的反硝化、固氮、大气和河流输入以及大规模循环造成的氮扩散。使用 N* [Gruber 和 Sarmiento，1997] 和水团年龄示踪剂计算出热带太平洋东部的水柱反硝化率为 48 +/- 5 Tg N yr(-1)。根据文献中的速率，我们估计沉积反硝化作用可额外去除 15 +/- 3 Tg N yr(-1)。然后，我们计算由于流经盆地的大规模环流而产生的总氮散度，该环流由流经南纬 32 度纬向断面以及流经印度尼西亚和白令海峡的流量组成。添加大气沉降和河流通量会导致流域的氮净差异为 -4 +/- 12 Tg N yr(-1)。假设稳定状态，太平洋固氮可以作为总预算的剩余部分提取。我们发现，为了平衡太平洋氮预算，固氮必须贡献 59 +/- 14 Tg N yr(-1)。这一结果与 Gruber 和 Sarmiento [1997] 基于北大西洋固氮率估计的初步全球推断一致。我们估计的平均面积固定率在夏威夷附近单个地点的直接和地球化学固定率估计范围内[Karl et al., 1997]。太平洋固氮主要发生在副热带环流的西部，那里发现了升高的 N* 信号。这些地区还通过大气尘埃沉积获得了大量的铁，这为固氮部分受到铁供应调节的假设提供了定性支持。
We establish the fixed nitrogen budget of the Pacific Ocean based on nutrient fields from the recently completed World Ocean Circulation Experiment (WOCE). The budget includes denitrification in the water column and sediments, nitrogen fixation, atmospheric and riverine inputs, and nitrogen divergence due to the large-scale circulation. A water column denitrification rate of 48 +/- 5 Tg N yr(-1) is calculated for the Eastern Tropical Pacific using N* [Gruber and Sarmiento, 1997] and water mass age tracers. On the basis of rates in the literature, we estimate sedimentary denitrification to remove an additional 15 +/- 3 Tg N yr(-1). We then calculate the total nitrogen divergence due to the large scale circulation through the basin, composed of flows through a zonal transect at 32 degreesS, and through the Indonesian and Bering straits. Adding atmospheric deposition and riverine fluxes results in a net divergence of nitrogen from the basin of -4 +/- 12 Tg N yr(-1). Pacific nitrogen fixation can be extracted as a residual component of the total budget, assuming steady state. We find that nitrogen fixation would have to contribute 59 +/- 14 Tg N yr(-1) in order to balance the Pacific nitrogen budget. This result is consistent with the tentative global extrapolations of Gruber and Sarmiento [1997], based on nitrogen fixation rates estimated for the North Atlantic. Our estimated mean areal fixation rate is within the range of direct and geochemical rate estimates from a single location near Hawaii [Karl et al., 1997]. Pacific nitrogen fixation occurs primarily in the western part of the subtropical gyres where elevated N* signals are found. These regions are also supplied with significant amounts of iron via atmospheric dust deposition, lending qualitative support to the hypothesis that nitrogen fixation is regulated in part by iron suppy.