Time-Series Measurements of the 13C/12C of Dissolved Inorganic Carbon

溶解无机碳(DIC)的13C/12C同位素比率已被证明是海洋中人为二氧化碳吸收的一个非常有用的示踪剂(Quay等人，1992；Heimann和Maier-Remer，1996；Sonnerup等人，2000；Quay等人，2003)。DIC的d13C的季节变化，加上DIC浓度和二氧化碳浓度的相应变化，已经被用来关闭表层海洋的碳收支(Zhang和Quay，1997；Gruber等，1998，Quay和Stutsman，正在出版中)。因此，d13C、DIC和pCO2的时间序列测量使人们能够区分造成海洋二氧化碳吸收速率年际变化的生物和物理原因，如Gruber等人所述。(2002)最近在BATS上演示。尽管有这些优势，但在副热带北大西洋(BATS)和北太平洋(热)只有两个地点存在这样的记录。这种海洋时间序列记录的缺乏严重限制了我们理解海洋人为二氧化碳吸收年际变化的原因的能力(Quay，2002)。与此形成鲜明对比的是，在100多个地点连续测量大气中的二氧化碳和d13C。在这个项目中，华盛顿大学的研究人员将在亚热带北部大西洋东部的第三个时间序列站点(ESTOC)开始每月的d13C测量。ESTOC的d13C记录将补充现场正在进行的DIC、二氧化碳和碱度测量，与BATS的d13C记录进行了非常有用的比较。格鲁伯等人。(2002)得出结论，百慕大二氧化碳吸收的年际变化与海表面温度(SST)和北大西洋涛动(NAO)大气循环指数密切相关。他们使用他们在BATS的d13C记录得出结论，净群落生产率(NCP)的年际变化与NAO有关。该项目的研究人员打算使用ESTOC拟议的d13C测量来计算NCP，并确定东副热带北大西洋的年际变化是否与百慕大的变化相关。研究小组还将继续其在HOT测量d13C的计划。我们在高温下长达十年的d13C记录表明，自1995年以来，表层海洋的d13C降幅翻了一番。自1995年以来，DIC增长率增加了两倍。然而，这种人为的二氧化碳吸收和d13C下降的明显加速发生在盐度最高的时期(1998年后)，夏季海温显著下降。这些剧烈的变化与1998年太平洋年代际涛动(PDO)气候指数由正(自1970年代末以来)转为负相关。这种相关性表明，北太平洋物理强迫(如温跃层深度、混合层深度、环流环流率)的变化可能改变了副热带海洋的碳收支。如果是这样的话，HOT的情况可能与格鲁伯等人的发现类似。(2002)在百慕大。该团队打算使用HOT的d13C测量来确定DIC的加速增加是否是HOT NCP率变化的结果。拟议的研究解决了一个主要的社会问题，即自然变异性如何影响海洋对人类产生的二氧化碳的吸收。未来气候变化中最大的人为控制因素是化石燃料燃烧和森林砍伐产生的二氧化碳。这项研究预计将产生一个海洋d13C数据集，该数据集将提供给广大科学界，并作为预测未来大气二氧化碳浓度的模型的有用验证测试。这项拟议的研究涉及美国碳循环科学计划(1999)的具体目标之一，即更好地量化和了解海洋对人为二氧化碳的吸收。拟议的工作从两个方面加强了研究和教育的基础设施。它与大加那利群岛拉斯帕尔马斯大学的科学家建立了合作关系，研究海洋的碳循环。它测试的设备可以被海洋学社区广泛使用，以远程收集海水样本进行碳分析。

ABSTRACTOCE-0327006The 13C/12C isotopic ratio of dissolved inorganic carbon (DIC) has been shown to be a very useful tracer of anthropogenic CO2 uptake in the ocean (Quay et al., 1992; Heimann and Maier-Reimer, 1996; Sonnerup et al., 2000; Quay et al., 2003). Seasonal changes in the d13C of DIC, coupled with corresponding changes in DIC concentration and pCO2, have been used to close the surface ocean.s carbon budget (Zhang and Quay, 1997; Gruber et al., 1998, Quay and Stutsman, in press). Time- series measurements of d13C, DIC and pCO2, therefore, allow one to separate biological from physical causes for interannual variations in the rate of oceanic CO2 uptake as Gruber et al. (2002) recently demonstrated at BATS. Despite these advantages, there are only two sites in the subtropical N. Atlantic (BATS) and N. Pacific (HOT) oceans where such records exist. This lack of ocean time series records has severely limited our ability to understand the causes of interannual variations in the ocean uptake of anthropogenic CO2 (Quay, 2002). In stark contrast, continuous records of atmospheric CO2 and d13C are being measured at over 100 sites.In this project, researchers at the University of Washington will initiate monthly d13C measurements at a third time-series site (ESTOC) in the eastern subtropical N. Atlantic. The d13C record at ESTOC, which will complement on-going measurements of DIC, pCO2 and alkalinity at the site, offers a very useful comparison to the BATS d13C record. Gruber et al. (2002) concluded that interannual variations in CO2 uptake at Bermuda correlated strongly with sea surface temperature (SST) and the North Atlantic Oscillation (NAO) index of atmospheric circulation. They used their d13C record at BATS to conclude that interannual variations in the rate of net community production (NCP) correlated with NAO. The researchers of this project intend to use the proposed d13C measurements at ESTOC to calculate NCP and determine whether interannual variations in the eastern subtropical N. Atlantic correlate with variations at Bermuda.The research team will also continue its program of d13C measurements at HOT. Our decade-long d13C record at HOT shows that the d13C decrease rate in the surface ocean has doubled since 1995. The DIC increase rate has tripled since 1995. However, this apparent acceleration of anthropogenic CO2 uptake and d13C decrease occurred during a period (post 1998) when salinity is the highest ever measured at HOT and summertime SST has decreased significantly. These dramatic changes at HOT correlate with a shift in the Pacific Decadal Oscillation (PDO) climate index in 1998 from positive (since the late 1970s) to negative. This correlation suggests that changes in physical forcing (e.g., thermocline depth, mixed layer depth, gyre circulation rates) in the N. Pacific may have changed the subtropical ocean.s carbon budget. If so, the situation at HOT may be similar to that found by Gruber et al. (2002) at Bermuda. The team intends to use d13C measurements at HOT to determine whether the accelerated DIC increase is a result of changes in the NCP rate at HOT.The proposed research addresses a major societal issue, that is, how natural variability affects the ocean.s uptake of anthropogenically produced CO2. The largest single human-controlled factor in future climate change is the production of CO2 from fossil fuel combustion and deforestation. The research is expected to yield an ocean d13C data set that will be made available to the broad scientific community and serve as a useful validation test for models predicting future atmospheric CO2 concentrations. The proposed research addresses one of the specific goals of the US Carbon Cycle Science Plan (1999), that is, to better quantify and understand the uptake of anthropogenic CO2 in the oceans. The proposed work enhances infrastructure for research and education in two ways. It establishes collaboration with scientists at the Universidad de Las Palmas in the Grand Canary Islands studying the ocean's carbon cycle. It tests equipment that could be broadly used by the oceanographic community to remotely collect seawater samples for carbon analysis.