Quantifying ocean oxygen-to-carbon demand by chemical analyses and inverse models

通过光合作用和呼吸过程中氧气的产生和消耗，海洋碳和氧循环密切相关。每摩尔呼吸有机碳消耗的氧气量，即呼吸商，是准确预测海洋氧气浓度以及海洋氧气水平如何响应气候变化的关键。尽管如此重要，呼吸商很少被直接测量。本研究的目的是估计呼吸商及其在海洋区域和深度上的变化。这将通过整合从多个海洋区域收集的颗粒有机物质的直接化学测量，以及通过使用海洋环流模型来间接分析全球溶解氧和碳浓度数据库的环流模型来实现。除了促进科学界对海洋氧循环的理解外，该项目还将为研究人员和学生提供研究培训。该项目还将提高公众对未来海洋氧浓度可能变化的认识和理解。预测当前和未来氧水平的主要不确定性之一是生物呼吸需求的调节。呼吸商描述了消耗一摩尔有机碳所需的氧气量，因此是碳和氧循环之间的关键环节。在这里，我们建议使用一种新开发的化学技术来测量来自地表和温跃层的颗粒有机物（POM）中每摩尔呼吸有机碳所消耗的氧气量，即呼吸商。因此，我们的目标是获得呼吸商在不同的海洋制度和深度的新的直接化学测量。随后，我们建议将这些观测结果纳入使用全球水文示踪剂浓度数据的季节性分解逆模型。这种综合方法将提供POM储量和出口通量中呼吸商的平均和区域变率的第一个全球尺度估计（和不确定性）。将应用将呼吸商与区域或环境变量联系起来的不同参数化来测试它们如何影响和复制全球氧浓度以及氧最小带的范围。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The marine carbon and oxygen cycles are intimately linked through the production and consumption of oxygen during photosynthesis and respiration. The amount of oxygen consumed per mole of respired organic carbon, the respiration quotient, is key for accurately predicting ocean oxygen concentrations and how ocean oxygen levels will respond to climate change. Despite this importance, the respiration quotient has rarely been measured directly. The aim of this research is to estimate the respiration quotient and its variability across ocean regions and depth. This will be done through an integration of direct chemical measurements of particulate organic matter collected from multiple ocean regions and indirectly by using an ocean circulation model to analyze a global database of dissolved oxygen and carbon concentration with a circulation model. In addition to advancing the understanding of the ocean oxygen cycle in the scientific community, this project will provide research training for researchers and students. The project will also improve awareness and understanding in the general public about possible future changes to marine oxygen concentrations.One of the main uncertainties in predicting current and future oxygen levels is the regulation of the biological respiration demand. The respiration quotient describes the amount of oxygen needed during the consumption of one mole of organic carbon and thus is a key link between the carbon and oxygen cycles. Here, we propose to measure the amount of oxygen consumed per mole of respired organic carbon, the respiration quotient, in particulate organic matter (POM) from the surface and thermocline using a newly developed chemical technique. Thus, we aim to obtain new direct chemical measurements of the respiration quotient across distinct oceanic regimes and depths. Subsequently, we propose to incorporate these observations into a seasonally-resolved inverse model using global hydrographic tracer concentration data. This combined approach will provide the first global-scale estimates (and uncertainties) of the mean and regional variability of the respiration quotient in the POM stock and export flux. Different parameterizations linking the respiration quotient to regions or environmental variables will be applied to test how they impact and replicate global oxygen concentrations and the extent of the oxygen minimum zones.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.