Methane (CH₄) is one of the most powerful greenhouse gases with the capacity to influence the Earth's radiative budget as well as contribute to atmospheric chemistry. Natural oceanic production makes up to ∼4% of the overall global CH₄ emissions, however, there is uncertainty around the accuracy of this value due to a lack of accurate measurements. Such is the case in the Subtropical Eastern South Pacific Ocean (SESP), a region with pronounced chlorophyll‐a and oxygen gradients, which in turn affect the microbial CH₄ cycling. This study was conducted during spring‐summer (2014–2016) in the SESP. The region (∼17°–37°S/71°–110°W) is separated into (i) eutrophic, (ii) mesotrophic, and (iii) oligotrophic areas, according to oceanographic and biogeochemical criteria. The SESP presents high CH₄ zonal variability with levels ranging from 0.63 to 33.4 nmol L⁻¹, corresponding to 29% and 1,423% saturation, respectively. High CH₄ concentrations (>1,000% saturation) are observed in the narrow eutrophic area subjected to coastal upwelling. These conditions clearly differ to those observed in the extended oligotrophic subtropical gyre (∼100% saturation). Furthermore, CH₄ also tends to accumulate in the mesotrophic area (with upto 1,423% saturation), where oceanographic conditions as stratification, mesoscale eddies and island mass effect could trigger the presence of a microbial biomass that may be able to induce CH₄ regeneration. The CH₄ efflux is estimated to be between 0.13 and 19.1 µmol m⁻² d⁻¹ (mean ± SD = 4.72 ± 4.67) and the SESP has an emission rate of ∼87.9 Gg CH₄ yr⁻¹.

中文翻译：

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南亚热带东太平洋（17°至37°S）极端海洋梯度上溶解甲烷的空间分布

甲烷（CH ₄）是最强大的温室气体之一，具有影响地球辐射预算以及促进大气化学的能力。天然海洋产量约占全球总CH ₄排放量的约₄％，但是由于缺乏精确的测量结果，该值的准确性存在不确定性。在亚热带东太平洋（SESP）中就是这种情况，该区域的叶绿素a和氧梯度明显，反过来又会影响微生物CH ₄骑自行车。这项研究是在SESP的春夏（2014-2016年）期间进行的。根据海洋学和生物地球化学标准，该地区（〜17°–37°S / 71°–110°W）被划分为（i）富营养化，（ii）中营养化和（iii）贫营养化区域。SESP表现出高CH ₄纬向变异性，水平范围为0.63至33.4 nmol L ^-1，分别对应于29％和1,423％的饱和度。在狭窄的富营养区，发生沿海上升流，观测到较高的CH ₄浓度（> 1,000％饱和度）。这些条件明显不同于在亚营养的亚营养环中（〜100％饱和度）所观察到的条件。此外，CH ₄甲烷也趋向于在中营养区域（饱和度高达1,423％）积累，在该区域，分层，中尺度涡旋和岛屿质量效应等海洋学条件可能会触发可能诱导CH ₄再生的微生物生物量的存在。CH _4的流出量估计在0.13和19.1 µmol m ^-2  d ^-1之间（平均值±SD = 4.72±4.67），并且SESP的发射速率约为87.9 Gg CH ₄  yr ^-1。