Impact of Anthropogenic Nitrogen Deposition on Oceanic Nitrous Oxide

一氧化二氮是一种温室气体，也在减少平流层臭氧方面发挥作用。它是在海洋中通过细菌的作用产生的，细菌作用于有机质分解过程中形成的海洋化学物种。化石燃料的燃烧和氮基化肥的应用向大气中释放出活性氮物种。这些活性氮物种可以通过气流在开阔的海洋上输送，在那里它们被沉积在海洋表面。在这里，它们为海洋微生物提供了一种新的氮素营养来源，然后海洋微生物可以生产更多的海洋有机物。这种“额外的”有机物的分解作用是从海洋向大气中释放出额外的一氧化二氮来源，在那里它可以影响地球的辐射平衡(通过其温室气体的作用)，或者进入平流层增加臭氧消耗。最近的一项研究试图量化由于化石燃料使用量和化肥使用量的预期增加而导致的一氧化二氮海洋通量的潜在增加。研究人员缺乏一个现实的海洋生物学模型，该模型也代表了控制一氧化二氮形成的过程，因此用简单的线性化计算来估计增加的大气通量。在这项提议中，我们计划建立一个控制海洋一氧化二氮形成(和破坏)过程的现实全球模型；一个能够描述一氧化二氮循环过程、海洋生物和海洋环流之间相互作用的时空变化的模型。该模型将扩展UEA现有的海洋生物学模型(PlankTOM)。我们将使用组合模型来估计从海洋到大气的一氧化二氮通量的变化，以应对未来增加向海洋添加活性氮的情况。虽然这项建议侧重于一氧化二氮的后果，但我们计划建立的建模工具可以应用于涉及海洋生物、其他温室气体(如二氧化碳)和气候相互作用的广泛问题。

Nitrous oxide is a greenhouse gas and also plays a role in reducing ozone in the stratosphere. It is produced in the ocean through the action of bacteria which act on oceanic chemical species formed during the breakdown of organic matter. The burning of fossil fuels and the application of nitrogen based fertilisers releases reactive nitrogen species into the atmosphere. These reactive nitrogen species can be transported by air currents over the open ocean where they are deposited on the ocean surface. Here they provide a source of 'new' nitrogen nutrients for the oceanic micro-organisms which can then produce additional oceanic organic matter. The breakdown of this 'additional' organic matter acts to release an additional source of nitrous oxide from the ocean to the atmosphere, where it can affect the earth's radiation balance (through its role as a greenhouse gas), or travel to the stratosphere and increase ozone depletion. A recent study has attempted to quantify the potential increases in ocean fluxes of nitrous oxide caused by predicted increases of fossil fuel use and fertiliser application. The investigators lacked a realistic model of ocean biology which also represented the processes governing the formation of nitrous oxide, and so estimated the increased flux to the atmosphere with a simple linearised calculation. In this proposal we plan to build a realistic global model of the processes controlling oceanic nitrous oxide formation (and destruction); a model with the ability to represent the spatial and temporal variations of the interactions between nitrous oxide cycling processes, ocean biology and ocean circulation. This model will extend an existing ocean biology model (PlankTOM) at UEA. We will use the combined model to estimate the changes in nitrous oxide fluxes from the ocean to the atmosphere for future scenarios of increased reactive nitrogen addition to the ocean. Although this proposal focuses on the consequences for nitrous oxide, the modelling tool we plan to build can be applied to a broad range of problems involving the interactions of ocean biology, other greenhouse gases such as CO2, and climate.