Testing model estimates of recent ocean carbon uptake and deoxygenation using atmospheric and oceanic data

模式研究表明，全球变暖可能通过海洋环流和碳化学的变化减少海洋对二氧化碳的吸收，并导致海洋内部溶解的O2减少，导致O2最小带的扩大。这些过程可能已经在进行中，以应对过去几十年的变暖和风的变化。在这个项目中，斯克里普斯海洋学研究所的研究人员将测试海洋模型对空气-海洋O2和CO2交换的模拟，采用一种强调大气O2/N2比率和CO2浓度的综合测量以及海洋氯氟化碳（CFCs）测量的限制的方法。该方法基于计算示踪剂“大气势氧”（APO）， APO实际上是O2 + 1.1CO2的加权和。从结构上看，APO对陆地生物圈中CO2和O2的交换不敏感。斯克里普斯和普林斯顿O2项目的观测表明，APO在过去二十年中以精确测量的速率下降。APO减少的两个组成部分已得到很好的理解：(1)化石燃料组成部分和(2)与海洋对人为CO2的吸收有关的组成部分，这可以根据对氟氯化碳的海洋观测来估计。这两个组成部分都可以精确地量化，并且一起似乎高估了观察到的APO减少。剩余APO的变化限制了不被认为是人为的O2和CO2的海气交换，即由于气候对海洋的影响。因此，APO趋势与量化海洋CO2和O2的持续变化直接相关。该提案的核心活动将涉及基于观察到的APO变化开发和应用数据目标进行模型验证。斯克里普斯的研究人员将与四个海洋模拟小组密切合作，获得模拟过去几十年里因气候变化和二氧化碳上升而导致的大气和海洋中O2和CO2交换的模型运行结果。他们不仅将测试模式对APO长期趋势的解释能力，还将测试与控制中高纬度O2交换的过程有关的季节周期。更广泛的影响：这项工作将有助于巩固对两个迫在眉睫和相关的环境威胁的科学认识：二氧化碳上升的气候放大和海洋脱氧。它还将通过维持一个小但可行的建模组件来补充正在进行的Scripps O2项目的测量活动。该计划将通过公开演讲向公众传播前沿研究，并通过支持一名年轻科学家和一名研究生，帮助培养年轻人才。

Model studies suggest that global warming may reduce the ocean uptake of CO2 via changes in ocean circulation and carbon chemistry and lead to reductions of dissolved O2 in the ocean interior, causing an expansion of O2 minimum zones. These processes are possibly already underway in response to warming and wind changes over the past few decades. In this project, researchers at the Scripps Institution of Oceanography will test ocean model simulations of air-sea O2 and CO2 exchange using an approach emphasizing constraints from combined measurements of atmospheric O2/N2 ratio and CO2 concentrations and ocean measurements of chloro-fluorocarbons (CFCs). The approach is based on computing tracer "atmospheric potential oxygen" (APO), which is effectively the weighted sum O2 + 1.1CO2. By construction, APO is insensitive to land biospheric exchanges of CO2 and O2. Observations by the Scripps and Princeton O2 programs show that APO has decreased over the past two decades at a precisely measured rate. Two components of the APO decrease are well understood: (1) a fossil-fuel component and (2) a component related to uptake of anthropogenic CO2 by the oceans, which can be estimated based on ocean observations of CFCs. These two components can both be precisely quantified, and together appear to overestimate the observed APO decrease. The residual APO change constrains the air-sea exchanges of O2 and CO2 not counted as anthropogenic, i.e. due to climate impacts on the oceans. The APO trend is thus directly relevant to quantifying ongoing changes in ocean CO2 and O2. A core activity of this proposal will involve developing and applying data targets for model validation based on the observed APO changes. Working closely with four ocean modeling groups, the Scripps researchers will acquire output of model runs that simulate air-sea exchange of O2 and CO2 over the past few decades in response to climate changes and rising CO2. They will test not only the ability of the models to account for the long-term trends in APO but also for the seasonal cycles, which relate to the processes controlling O2 exchange at middle and high latitudes. Broader Impacts: This work will help to solidify the scientific understanding of two looming and related environmental threats: climate amplification of rising CO2 and ocean deoxygenation. It will also complement ongoing measurement activities of the Scripps O2 program by sustaining a small but viable modeling component. The project will enable dissemination of cutting edge research to the public at large through public presentations and will help foster young talent through support for a young scientist and a graduate student.