High Resolution Underway Nitrous Oxide Measurements (atmosphere) during METEOR cruise M98

The Benguela Upwelling System (BUS) is the most productive of all eastern boundary upwelling ecosystems and it hosts a well-developed oxygen minimum zone. As such, the BUS is a potential hotspot for production of N2O, a potent greenhouse gas derived from microbially driven decay of sinking organic matter. Yet, the extent at which near-surface waters emit N2O to the atmosphere in the BUS is highly uncertain. Here we present the first high-resolution surface measurements of N2O across the northern part of the BUS (nBUS).We found strong gradients with a threefold increase in N2O concentrations near the coast as compared with open ocean waters. Our observations show enhanced sea-to-air fluxes of N2O (up to 1.67 nmol m−2 s−1) in association with local upwelling cells. Based on our data we suggest that the nBUS can account for 13% of the total coastal upwelling source of N2O to the atmosphere

本格拉上升流系统（Benguela Upwelling System, BUS）是所有东边界上升流生态系统中生产力最高的，且发育有成熟的氧最低区（oxygen minimum zone）。因此，本格拉上升流系统是一氧化二氮（N₂O）的潜在产生热点——这种强效温室气体源自沉降有机质的微生物驱动降解。然而，本格拉上升流系统中近表层海水向大气排放一氧化二氮的规模仍存在高度不确定性。本研究首次获取了本格拉上升流系统北部（northern BUS, nBUS）区域高分辨率的一氧化二氮表层观测数据。研究发现该区域存在显著的浓度梯度：近岸海域的一氧化二氮浓度较开阔大洋升高至三倍。观测结果显示，伴随局地上升流单元，一氧化二氮的海-气通量显著增强，最高可达1.67 nmol·m⁻²·s⁻¹。基于本次观测数据，本研究提出，本格拉上升流系统北部可贡献全球沿岸上升流源一氧化二氮大气排放总量的13%