CYCLING OF DISSOLVED ORGANIC MATTER IN THE PACIFIC AND ATLANTIC OCEANS USING RADIOCARBON

溶解有机碳是海洋中最大的碳库，相当于大气中的总碳含量。放射性碳是碳的放射性同位素，可以提供有关环境中碳循环的来源和时间尺度的信息。因此，了解溶解有机碳的碳同位素特征对于理解溶解有机碳循环的地球化学和动力学是重要的，并且对于碳循环模拟社区是必不可少的。这项研究的主要目的是确定在太平洋和大西洋地区的海水样品中溶解的有机碳的放射性碳值，很少或没有数据提供急需的，定量信息的时间尺度上溶解的有机碳在海洋中的循环。大气中的碳最终会进入海洋，因此，提高我们对影响其在深海长期储存的过程的理解至关重要。这项研究的结果将用于评估目前和未来大气二氧化碳浓度及其对海洋地球化学影响的模型。这项研究还将支持一名研究生和两名本科生的工作，并提供实践经验，将他们作为科学家和教育工作者的职业生涯做好准备。深海溶解有机碳（DOC）的平均放射性碳（14 C）年龄范围从4000年到6500年。以往的研究表明，南太平洋深层DOC 14 C与北太平洋深层DOC 14 C相当，表明南太平洋亚热带存在不稳定DOC的汇。此外，爆炸后马尾藻海沃茨DOC含量在年代际尺度上呈下降趋势。这些结果表明，其他的水团循环控制DOC 14 C在深海的过程。在这项研究中，来自加州大学欧文分校的研究人员将使用来自太平洋和大西洋的海水样品来检验两个假设：（1）在太平洋深海盆地的所有纬度上，散装DOC的放射性碳都是相似的，并且在南大洋的值更高，这表明DOC老化、矿化和年轻DOC注入伴随着深海环流的双重治理;（2）北大西洋深层DOC放射性碳值反映了爆炸后碳含量的变化。为了验证这些假设，将分析海水样品中的DOC同位素特征，从太平洋和大西洋的配置文件，建立一个定量的了解DOC在海洋中循环的时间尺度。这项研究解决了全球碳循环和DOC在海洋中的动态性质的知识的根本差距。

Dissolved organic carbon is the largest pool of carbon in the ocean, comparable to the total carbon content in the atmosphere. Radiocarbon, a radioactive isotope of carbon, can provide information on the source and timescale of carbon cycling in the environment. Therefore, knowing the carbon isotopic signatures of dissolved organic carbon is important for understanding the biogeochemistry and dynamics of dissolved organic carbon cycling, and is essential for the carbon cycle modeling community. The main objective of this research is to determine the radiocarbon values of dissolved organic carbon in seawater samples from areas in the Pacific and Atlantic Oceans for which little or no data is available to provide much needed, quantitative information on the timescale of dissolved organic carbon cycling in the ocean. Atmospheric carbon will end up in the ocean, and it is critical to improve our understanding of the processes that influence its long-term storage in the deep sea. Results of this research will be made available for use in models that assess present and future concentrations of atmospheric carbon dioxide and its impact on ocean biogeochemistry. This research will also support the work of one graduate student and two undergraduate students and provide hands-on experience that will prepare them for careers as scientists and educators.The average radiocarbon (14C) age of dissolved organic carbon (DOC) in the deep ocean ranges from 4000 to 6500 years. Previous research indicates that DOC 14C in the deep South Pacific is equal to that in the deep North Pacific, suggesting that there is a sink for labile DOC in the subtropical South Pacific, In addition, findings suggest that the content of post-bomb DOC has decreased in Sargasso Sea waters on decadal timescales. These findings indicate that processes other than water mass circulation controls DOC 14C in the deep sea. In this study, a researcher from the University of California, Irvine, will use seawater samples from the Pacific and Atlantic Oceans to test two hypotheses: (1) Radiocarbon of bulk DOC is similar at all latitudes of the deep Pacific basin, and values are higher in the Southern Ocean, suggesting the dual governance of DOC aging, remineralization, and young DOC injection concomitant with deep ocean circulation; (2) Deep DOC radiocarbon values in the North Atlantic Ocean reflect the presence of variable amounts of post-bomb carbon. To test these hypotheses, seawater samples will be analyzed for DOC isotopic signatures in profiles from Pacific and Atlantic Oceans to establish a quantitative understanding of the timescale of DOC cycling in the ocean. This study addresses fundamental gaps in knowledge of the global carbon cycle and the dynamic nature of DOC in the ocean.