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Collaborative research: US GEOTRACES PMT: Measuring the d13C-DIC distribution and estimating organic matter export rates

合作研究：美国GEOTRACES PMT：测量d13C-DIC分布并估算有机物出口率

基本信息

批准号：
1736598
负责人：
Paul Quay
金额：
$ 46.24万
依托单位：
University of Washington
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2017
资助国家：
美国
起止时间：
2017-08-01 至 2021-07-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1736598&HistoricalAwards=false
关键词：
Collaborative research US GEOTRACES PMT

项目摘要

The concentration of carbon dioxide gas (CO2) in the ocean depends in part on the rate of photosynthesis in the ocean because CO2 is consumed by microscopic plants in surface ocean (phytoplankton). The photosynthesis reaction can be written as CO2 + H2O + light energy - CH2O (sugar) + O2. During photosynthesis, the plankton preferentially consume CO2 molecules comprised of 12C atoms and less so CO2 molecules comprised of 13C atoms. Measuring the ratio of 13CO2 to 12CO2 dissolved in seawater provides a means to estimate the photosynthesis rate. Below the surface layer where photosynthesis occurs (the photic layer), bacteria use sinking plankton material for food and energy via a process called respiration (which is the reverse of the photosynthesis reaction). Respiration produces CO2 in the deeper layers of the ocean. The goal of our research is to measure the concentration of 13CO2 and 12CO2 in seawater from the surface to the bottom of the Pacific Ocean along a cruise path that starts in Seward, Alaska and goes southward to Tahiti. We will use these measurements to understand how photosynthesis, respiration and mixing in the ocean control the distributions of 13CO2 and 12CO2. The broader impact of our research is to determine how photosynthesis, respiration and mixing in the ocean affect the transfer rate of CO2 from the atmosphere to the ocean. This CO2 transfer rate is important because it affects the concentration of CO2, a greenhouse gas, in the atmosphere and the increasing acidity of the ocean. Other broader impacts include incorporating results from this study into classes taught by the researcher. One undergraduate student from the University of Washington would be supported and trained as part of this project.The specific goal of our research is to measure the depth distribution of the 13C/12C of the dissolved inorganic carbon (DIC) during the GEOTRACES PMT cruise (Seward, AK to Tahiti) in the N. Pacific Ocean. We intend to collect and measure d13C-DIC on ~850 seawater samples. The PMT section will cross a wide range of biological productive regimes from the oligotrophic gyres near Tahiti and Hawaii to the more productive HNLC regions in the equatorial and subarctic oceans. The expected meridional variations in productivity should provide the opportunity to determine the impact of organic matter (OM) export and subsequent degradation at depth on upper ocean distribution of d13C-IC, trace elements (TEs), and nutrients along the PMT section. We intend to determine how the meridional variations in productivity and proximity to outcropping water masses affect the distributions of d13C, PO4, NO3 and bioactive TEs (like Cadmium) throughout the thermocline and deep sea along the PMT cruise track. Improving our understanding of the processes that control d13C, TEs and nutrient distributions in the modern ocean will improve our ability to use d13C and TEs measurements in the sedimentary record as tracers of past changes in the ocean circulation and carbon cycling. From a broader impact perspective, our address research addresses two basic goals of the GEOTRACES program. First, to determine global ocean distributions of selected trace elements and isotopes and evaluate the sources, sinks, and internal cycling of these species to characterize more completely the physical, chemical and biological processes regulating their distributions. Second, to understand the processes that control the concentrations of geochemical species used for proxies of the ocean's past environment which will benefit the paleoceanography community.

海洋中二氧化碳 (CO2) 的浓度部分取决于海洋中光合作用的速率，因为二氧化碳被海洋表层的微观植物（浮游植物）消耗。光合作用反应可写为CO2+H2O+光能-CH2O（糖）+O2。在光合作用过程中，浮游生物优先消耗由 12 C 原子组成的 CO2 分子，较少消耗由 13 C 原子组成的 CO2 分子。测量海水中溶解的 13CO2 与 12CO2 的比率提供了估计光合作用速率的方法。在发生光合作用的表层（光层）下方，细菌通过呼吸作用（与光合作用反应相反）的过程，利用下沉的浮游生物物质获取食物和能量。呼吸作用在海洋深层产生二氧化碳。我们研究的目标是沿着从阿拉斯加苏厄德向南到达塔希提岛的巡航路径，测量从太平洋表面到海底的海水中 13CO2 和 12CO2 的浓度。我们将利用这些测量来了解海洋中的光合作用、呼吸和混合如何控制 13CO2 和 12CO2 的分布。我们研究的更广泛影响是确定海洋中的光合作用、呼吸和混合如何影响二氧化碳从大气到海洋的转移速率。这种二氧化碳转移率很重要，因为它会影响大气中二氧化碳（一种温室气体）的浓度以及海洋酸度的增加。其他更广泛的影响包括将这项研究的结果纳入研究人员教授的课程中。作为该项目的一部分，华盛顿大学的一名本科生将得到支持和培训。我们研究的具体目标是测量北太平洋 GEOTRACES PMT 巡航（阿拉斯加州苏厄德至塔希提岛）期间溶解的无机碳 (DIC) 的 13C/12C 的深度分布。我们打算收集并测量约 850 个海水样本的 d13C-DIC。 PMT部分将跨越广泛的生物生产区域，从塔希提岛和夏威夷附近的贫营养环流到赤道和亚北极海洋中生产力更高的HNLC区域。生产力的预期经向变化应提供机会确定有机质 (OM) 输出和随后的深度降解对沿 PMT 剖面的 d13C-IC、微量元素 (TE) 和营养物的上层海洋分布的影响。我们打算确定生产力的经向变化和与露头水团的接近程度如何影响沿 PMT 巡航轨迹的整个温跃层和深海中 d13C、PO4、NO3 和生物活性 TE（如镉）的分布。提高我们对现代海洋中控制 d13C、TE 和营养物分布的过程的理解，将提高我们使用沉积记录中的 d13C 和 TE 测量作为海洋环流和碳循环过去变化的示踪剂的能力。从更广泛的影响角度来看，我们的地址研究解决了 GEOTRACES 计划的两个基本目标。首先，确定选定的微量元素和同位素的全球海洋分布，并评估这些物种的源、汇和内部循环，以更全面地表征调节其分布的物理、化学和生物过程。其次，了解控制用于代表海洋过去环境的地球化学物种浓度的过程，这将有利于古海洋学界。