The imprint of anthropogenic activities on the marine nitrogen (N) cycle remains challenging to represent in global models, in part because of uncertainties regarding the source of marine N to the atmosphere. While N inputs of terrestrial origin present a truly external perturbation, a significant fraction of N deposition over the ocean arises from oceanic ammonia (NH₃) outgassing that is subsequently deposited in other ocean regions. Here, we describe advances in the Geophysical Fluid Dynamics Laboratory’s (GFDL) Earth System Model 4 (ESM 4.1) aimed at improving the representation of the exchange of N between atmosphere and ocean and its response to changes in ocean acidity and N deposition. We find that the simulated present‐day NH₃ outgassing (3.1 TgN yr^‐1) is 7% lower than under preindustrial conditions, which reflects the compensating effects of increasing CO₂ (‐16%) %not solely acidification and N enrichment of ocean waters (+9%). This change is spatially heterogeneous, with decreases in the open ocean (‐13%) and increases in coastal regions (+15%) dominated by coastal N‐enrichment. The ocean outgassing of ammonia is shown to increase the transport of N from N‐rich to N‐poor ocean regions, where carbon export at 100m increases by 0.5%. The implications of the strong response of NH₃ ocean outgassing to CO₂ for the budget of NH₃ in the remote marine atmosphere and its imprint in ice cores are discussed.

中文翻译：

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海洋氨放气：通过CO2和人为氮沉积进行调节

在全球模型中，人为活动在海洋氮（N）循环上的印记仍然具有挑战性，部分原因是由于海洋氮向大气中的来源存在不确定性。陆地来源的N输入确实表现出真正的外部扰动，而海洋中N的很大一部分沉积则来自海洋氨（NH ₃）脱气，该气体随后沉积在其他海洋区域中。在这里，我们描述了地球物理流体动力学实验室（GFDL）的地球系统模型4（ESM 4.1）的进展，该模型旨在改进大气与海洋之间N交换的表达及其对海洋酸度和N沉积变化的响应。我们发现模拟的现今NH ₃脱气（3.1 TgN yr ^-1）比工业化前的情况低7％，这反映出CO ₂（‐16％）增加的补偿作用不仅是酸化和海水富氮（+ 9％）。这种变化在空间上是异质的，在以海洋氮素富集为主的开放海洋中减少了13％，在沿海地区增加了15％。氨在海洋中的逸出表明增加了氮从富氮向贫氮的海洋区域的运输，在该区域，100m处的碳出口增加了0.5％。NH的强烈反应的影响₃海洋放气到CO ₂为NH的预算₃在远程海洋大气及其在冰芯印记进行了讨论。