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，与大气中的总碳含量相当。放射性碳是碳的一种放射性同位素，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了解溶解有机碳循环的生物地球化学和动力学具有重要意义，对于碳循环模拟社区也是至关重要的。这项研究的主要目的是确定太平洋和大西洋地区海水样本中溶解有机碳的放射性碳值，这些地区的数据很少或根本没有数据来提供关于海洋中溶解有机碳循环时间尺度的定量信息。大气中的碳最终将进入海洋，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生物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，为他们成为科学家和教育工作者做好准备。深海中溶解有机碳(DOC)的平均放射性碳(14C)年龄从4000年到6500年不等。以往的研究表明，南太平洋深海的DOC 14C与北太平洋深海的DOC相当，说明南太平洋副热带海域存在不稳定的DOC汇，此外，研究结果还表明，炸后马尾藻海DOC的含量在年代际尺度上有所下降。这些发现表明，深海中DOC14C是由水团环流以外的其他过程控制的。在这项研究中，来自加州大学欧文分校的一位研究人员将使用太平洋和大西洋的海水样本来检验两个假设：(1)太平洋盆地所有纬度的散装DOC的放射性碳相似，南大洋的值更高，表明DOC的老化、再矿化和年轻的DOC注入伴随着深海环流的双重治理；(2)北大西洋的深层DOC放射性碳值反映了炸弹后碳的存在。为了验证这些假设，将对太平洋和大西洋剖面中的海水样本进行DOC同位素特征分析，以建立对DOC在海洋中循环的时间尺度的定量理解。这项研究解决了在全球碳循环和海洋中DOC的动态性质方面的基本知识空白。

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.