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

使用放射性碳循环太平洋和大西洋中的溶解有机物

• 批准号: 1458941
• 负责人: Ellen Druffel
• 金额: $ 64.01万
• 依托单位: University of California-Irvine
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-03-01 至 2019-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1458941&HistoricalAwards=false
• 关键词: CYCLING; DISSOLVED; ORGANIC; MATTER; PACIFIC

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.

溶解的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，可以提供环境中碳循环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理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，对碳循环建模具有重要意义。本研究的主要目的是确定来自太平洋和大西洋地区的海水样品中溶解有机碳的放射性碳值，这些地区的数据很少或没有数据，以提供海洋中溶解有机碳循环时间尺度的急需的定量信息。大气中的碳最终会进入海洋，提高我们对影响其在深海长期储存的过程的理解是至关重要的。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式。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。深海溶解有机碳（DOC）的平均放射性碳（14C）年龄在4000 ~ 6500年之间。以往的研究表明，南太平洋深处的DOC 14C与北太平洋深处的DOC 14C相等，表明副热带南太平洋存在不稳定DOC的汇。此外，研究结果表明，在年代际尺度上，马尾藻海水中爆炸后DOC的含量有所下降。这些发现表明，深海DOC - 14C受水团环流以外的过程控制。在本研究中，加州大学欧文分校的研究人员将利用太平洋和大西洋的海水样本验证两个假设：(1)在太平洋深海盆的所有纬度，大量DOC的放射性碳值相似，且在南大洋较高，表明深海环流伴随DOC老化、再矿化和年轻DOC注入的双重治理；(2)北大西洋深海DOC放射性碳值反映了爆炸后碳的变化量。为了验证这些假设，将分析来自太平洋和大西洋的海水样本中的DOC同位素特征，以建立对海洋中DOC循环时间尺度的定量理解。这项研究解决了全球碳循环知识和海洋DOC动态性质的基本空白。