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

海洋中二氧化碳气体（CO2）的浓度部分取决于海洋中光合作用的速率，因为CO2被海洋表面的微生物（浮游植物）消耗。光合作用反应可以写成CO2 + H2O +光能-CH 2 O（糖）+ O2。 在光合作用期间，浮游生物优先消耗由12 C原子组成的CO2分子，而较少消耗由13 C原子组成的CO2分子。 测量溶解在海水中的13 CO2与12 CO2的比率提供了一种估计光合作用速率的方法。在光合作用发生的表层（光层）之下，细菌通过称为呼吸的过程（这是光合作用反应的逆过程）将下沉的浮游生物材料用作食物和能量。 呼吸作用在海洋深层产生二氧化碳。我们的研究目标是测量从太平洋表面到底部的海水中13 CO2和12 CO2的浓度，沿着沿着一条从阿拉斯加州苏厄德开始向南到塔希提岛的巡航路径。 我们将利用这些测量来了解海洋中的光合作用、呼吸作用和混合作用如何控制13 CO2和12 CO2的分布。我们研究的更广泛影响是确定海洋中的光合作用，呼吸作用和混合如何影响CO2从大气到海洋的传输速率。这种二氧化碳的转移率很重要，因为它会影响大气中二氧化碳（一种温室气体）的浓度和海洋酸度的增加。 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。 本研究的具体目标是测量GEOTRACES PMT巡航（从阿拉斯加州苏厄德到大溪地）期间溶解无机碳（DIC）的13 C/12 C深度分布。太平洋我们打算收集和测量约850个海水样品的d13 C-DIC。PMT部分将跨越从塔希提岛和夏威夷附近的寡营养环流到赤道和亚北极海洋中生产力更高的HNLC区域的广泛的生物生产机制。 生产力的预期纬向变化应提供机会，以确定有机质（OM）的出口和随后的深度d13 C-IC，微量元素（TE），和营养物沿着PMT部分的上层海洋分布退化的影响。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整个温跃层和深海中d 13 C、PO 4、NO3和生物活性TE（如镉）的分布，沿着PMT巡航轨迹。提高我们对现代海洋中控制d13 C、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d13 C和TE测量值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。 第一，确定全球海洋中某些微量元素和同位素的分布情况，并评价这些物种的来源、汇和内部循环，以更全面地描述调节其分布的物理、化学和生物过程。 第二，了解控制地球化学物种浓度的过程，这些物种用于海洋过去环境的代理，这将有利于古海洋学界。

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.