Equatorial transport of nitrous oxide from the eastern tropical Pacific Ocean

一氧化二氮（N2 O）是一种强大的温室气体，比二氧化碳强约300倍，也与臭氧层的破坏有关。因此，重要的是要了解N2 O的规模和来源，以预测未来的气候影响。海洋是大气中N2 O的重要来源，但其总体贡献尚不确定。大量的海洋N2 O输送到大气中来自热带东太平洋（ETP）。这个区域是整个海洋中氧气浓度最低的区域，这有利于N2 O的大量产生。以前的ETP扩散到大气中的N2 O的量的估计只考虑直接在ETP的高N2 O区域的区域。然而，有很强的次表层洋流，远离ETP，沿沿着赤道向西流动，在确定ETP对海洋排放N2 O的贡献时，忽略了这些赤道洋流中携带的N2 O。这项拟议的工作将使用全球海洋船舶水文调查计划（GO-SHIP）通过热带太平洋巡航收集的新的高质量N2 O数据，以调查整个热带太平洋的N2 O循环。低氧区域，如ETP，预计将在未来扩大，可能导致N2 O产量的增加，强调了解N2 O循环在该地区的重要性。该项目将支持指导多达两名本科生暑期实习生。海洋大气局/太平洋海洋环境实验室痕量气体小组最近在分析能力方面取得了进展，并将其应用于全球海洋船舶水文调查方案在热带太平洋进行的三次重复水文调查，这有助于收集质量和覆盖范围前所未有的一氧化二氮测量数据以及补充水文参数。我们建议使用这种新的，高质量的GO-SHIP N2 O数据与一氧化二氮的稳定同位素组成，示踪剂的通风率，和当前的速度，调查运输，生产和一氧化二氮在热带太平洋的流出。使用观测数据和理想化的建模，研究将（i）估计N2 O的物理传输到/从ETP的大小，和损失到大气中，和（ii）区分N2 O的来源在赤道电流之间的平流从ETP和原位生产。这里提出的工作将导致N2 O的生产，运输和命运在热带太平洋的一个更微妙的理解。这个奖项反映了NSF的法定使命，并已被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估的支持。

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.