Pathways of Nitrous Oxide Production in the Eastern Tropical South Pacific Oxygen Minimum Zone
Pathways of Nitrous Oxide Production in the Eastern Tropical South Pacific Oxygen Minimum Zone
复制标题
DOI：
10.1029/2022gb007670
复制
发表时间：
2023-06
影响因子：
5.2
通讯作者：
D. McCoy;P. Damien;D. Clements;Simon Yang;D. Bianchi
中科院分区：
文献类型：
--
作者：
D. McCoy;P. Damien;D. Clements;Simon Yang;D. Bianchi
海洋排放的一氧化二氮（N2O）约占所有自然源的三分之一。N2O释气的热点发生在氧最小区（OMZ）上，其中缺氧沃茨周围陡峭的氧梯度的存在导致硝化和反硝化产生的N2O增加。然而，这些途径的N2O生产和放气在这些地区的相对贡献仍然受到很大的限制，部分是由于共享的中间氮示踪剂，以及紧密耦合的反硝化源和汇。为了阐明这个问题，我们在热带南太平洋东部（ETSP）的三维涡旋分辨物理地球化学模型中嵌入了一个新的OMZ氮循环机制模型，跟踪远程平流，大气交换和局部硝化和反硝化的贡献。该模型表明，净N2O生产反硝化作用是大约一个数量级大于硝化作用内ETSP OMZ。然而，只有约32%的反硝化产生的N2O最终排放到该地区的大气中（每年占海气N2O通量的约36%），而其余的则被输出到该区域之外。相反，远程产生的N2O平流进入OMZ区域约占总N2O释气的一半（1057%），硝化作用的贡献较小（107%）。我们的研究结果表明，与反硝化作用增强生产一起，远程衍生的N2O的上涌贡献最大的ETSP OMZ的N2O释气。
Oceanic emissions of nitrous oxide (N2O) account for roughly one‐third of all natural sources to the atmosphere. Hot‐spots of N2O outgassing occur over oxygen minimum zones (OMZs), where the presence of steep oxygen gradients surrounding anoxic waters leads to enhanced N2O production from both nitrification and denitrification. However, the relative contributions from these pathways to N2O production and outgassing in these regions remains poorly constrained, in part due to shared intermediary nitrogen tracers, and the tight coupling of denitrification sources and sinks. To shed light on this problem, we embed a new, mechanistic model of the OMZ nitrogen cycle within a three‐dimensional eddy‐resolving physical‐biogeochemical model of the Eastern Tropical South Pacific (ETSP), tracking contributions from remote advection, atmospheric exchange, and local nitrification and denitrification. The model indicates that net N2O production from denitrification is approximately one order of magnitude greater than nitrification within the ETSP OMZ. However, only ∼32% of denitrification‐derived N2O production ultimately outgasses to the atmosphere in this region (contributing ∼36% of the air‐sea N2O flux on an annual basis), while the remaining is exported out of the domain. Instead, remotely produced N2O advected into the OMZ region accounts for roughly half (∼57%) of the total N2O outgassing, with smaller contributions from nitrification (∼7%). Our results suggests that, together with enhanced production by denitrification, upwelling of remotely derived N2O contributes the most to N2O outgassing over the ETSP OMZ.