Equatorial transport of nitrous oxide from the eastern tropical Pacific Ocean

一氧化二氮(N2O)是一种强大的温室气体，其强度约为二氧化碳的300倍，也与臭氧层的破坏有关。因此，重要的是要了解N2O对大气的影响程度和来源，以便预测未来的气候影响。海洋是大气中N2O的重要来源，但其总体贡献尚不确定。向大气输送的大量海洋N2O来自东热带太平洋(ETP)。这一地区是整个海洋中氧气浓度最低的地区，这有利于N2O的大量产生。以前对从ETP向大气扩散的N2O量的估计只考虑了ETP高N2O区域的直接区域。然而，在确定ETP对海洋N2O排放的贡献时，存在着从ETP向西沿赤道向西流动的强大次表层流，而从这些赤道流中带走的N2O被忽略了。这项拟议的工作将使用通过热带太平洋的3次全球海洋船基水文调查计划(GO-SHIP)收集的新的高质量N2O数据，以调查整个热带太平洋的N2O循环。像ETP这样的低氧区域预计将在未来扩大，潜在地导致N2O产量的增加，这突显了了解该地区N2O循环的重要性。该项目将支持指导最多两名本科生暑期实习生。NOAA/PMEL痕量气体小组在分析能力方面的最新进展，以及将其应用于三次全球海洋船基水文学调查方案(GO-SHIP)在热带太平洋的重复水文学测量，促进了对该区域前所未有质量和覆盖面的一氧化二氮测量的收集，以及补充的水文学参数。我们建议结合一氧化二氮稳定的同位素组成、通风率示踪剂和水流速度，利用这一新的高质量N2O数据来研究热带太平洋中一氧化二氮的运输、生产和外流。利用观测数据和理想化模拟，这项研究将(I)估计进出ETP的N2O的物理输送的大小，以及对大气的损失，以及(Ii)区分来自ETP的平流和现场产生的赤道洋流中N2O的来源。这里提出的工作将导致对热带太平洋N2O的产生、运输和命运有更细微的了解。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Nitrous oxide (N2O) is a powerful greenhouse gas, ~300 times stronger than carbon dioxide and is also implicated in the destruction of the ozone layer. Thus, it is important to understand the magnitude and sources of N2O to the atmosphere in order to predict future climate impacts. The ocean is a significant source of N2O to the atmosphere, but its overall contribution is uncertain. A significant amount of the marine N2O delivered to the atmosphere comes from the eastern tropical Pacific (ETP). This region is host to some of the lowest oxygen concentrations in the entire ocean, which is favorable to a massive production of N2O. Previous estimates of the amount of N2O diffusing out of the ETP to the atmosphere considered only the area directly over the high N2O region of the ETP. However, there are strong subsurface currents that flow away from the ETP, westward along the equator, and N2O carried away in these equatorial currents has been overlooked when determining the contribution of the ETP to marine emissions of N2O. This proposed work will use new, high-quality N2O data collected on 3 Global Ocean Ship-based Hydrographic Investigations Program (GO-SHIP) cruises through the tropical Pacific to investigate N2O cycling across the entire tropical Pacific Ocean. Low oxygen regions, like the ETP, are predicted to expand in the future, potentially leading to an increase in N2O production, underscoring the importance of understanding N2O cycling in this region. This project will support mentoring up to two undergraduate summer interns. Recent advances in analytical capabilities within the NOAA/PMEL Trace Gas group, and their application to three Global Ocean Ship-based Hydrographic Investigations Program (GO-SHIP) repeat hydrography cruises through the tropical Pacific, have facilitated the collection of nitrous oxide measurements of unprecedented quality and coverage of the region, together with complementary hydrographic parameters. We propose to use this new, high-quality GO-SHIP N2O data in concert with the stable isotopic composition of nitrous oxide, tracers of ventilation rates, and current velocities to investigate the transport, production, and efflux of nitrous oxide in the tropical Pacific Ocean. Using both observation data and idealized modeling, the research will (i) estimate the magnitude of the physical transport of N2O to/from the ETP, and losses to the atmosphere, and (ii) differentiate the sources of N2O in equatorial currents between advection from the ETP and in situ production. The work proposed here will lead to a more nuanced understanding of N2O production, transport, and fate in the tropical Pacific.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.