High Resolution Underway Nitrous Oxide Measurements (water) during METEOR cruise M99

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）是所有东部边界上升流生态系统中生产力最高的体系，且发育有成熟的低氧区（oxygen minimum zone）。正因如此，本格拉上升流系统是一氧化二氮（N₂O）生成的潜在热点区域——一氧化二氮是一种源自沉降有机质微生物降解过程的强效温室气体。但目前学界对本格拉上升流系统近岸表层海水向大气排放一氧化二氮的规模仍存在极大不确定性。本研究首次针对本格拉上升流系统北部区域（nBUS）开展了高分辨率的表层海水一氧化二氮观测。研究发现近岸海域的一氧化二氮浓度是远海海域的三倍，存在显著的浓度梯度。观测结果显示，伴随局地上升流单元，一氧化二氮的海-气通量显著升高，最高可达1.67纳摩尔每平方米每秒（nmol·m⁻²·s⁻¹）。基于本次观测数据，本研究认为本格拉上升流系统北部区域（nBUS）贡献了全球沿海上升流系统向大气排放一氧化二氮总量的13%。