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

海洋的碳循环和氧循环通过光合作用和呼吸作用中氧气的产生和消耗而密切联系在一起。每摩尔呼吸有机碳的耗氧量，即呼吸商，是准确预测海洋氧气浓度以及海洋氧气水平将如何应对气候变化的关键。尽管这很重要，但很少有人直接测量呼吸商。这项研究的目的是估计呼吸商及其跨海洋区域和深度的变异性。这将通过综合从多个海洋区域收集的颗粒状有机物的直接化学测量，并通过使用海洋环流模型分析具有环流模型的全球溶解氧和碳浓度数据库来间接实现。除了促进科学界对海洋氧循环的了解外，该项目还将为研究人员和学生提供研究培训。这项计划亦会提高公众对未来海洋含氧量可能发生的变化的认识和了解。预测现时和未来含氧量的其中一个主要不明朗因素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，因此是碳循环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每摩尔呼吸有机碳的氧耗量，即呼吸商，来自地表和温跃层的颗粒有机物(POM)。因此，我们的目标是获得不同海洋制度和深度的呼吸商的新的直接化学测量结果。随后，我们建议利用全球水文示踪剂浓度数据，将这些观测数据合并到一个季节性分解的逆模型中。这一综合办法将首次对POM储存和出口通量中呼吸商的平均和区域变异性提供全球规模的估计(和不确定性)。将呼吸商与地区或环境变量联系起来的不同参数将被应用来测试它们如何影响和复制全球氧气浓度以及氧气最小区域的范围。这一裁决反映了NSF的法定使命，并通过使用基金会的智力优势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.