Collaborative Research: CarboMODE: Carbon Dioxide Dynamics in Mode Water of the North Atlantic Ocean

模式水的形成，如北大西洋的18度水(EDW)，对于推动海洋环流、通风和将生物地球化学性质转移到海洋内陆非常重要。最近的研究表明，EDW在建立副热带环流的营养库方面发挥了重要作用[Jenkins和Doney，2003；Doney和Jenkins，2004；Palter等人，2005]，这对北大西洋副热带环流的营养和碳动态以及生产力具有重要意义。此外，EDW在海洋吸收和大气二氧化碳年代际变化方面具有潜在的重要作用[Bates等人，2002年]。在这项研究中，百慕大生物研究站(BBSR)和伍兹霍尔海洋研究所(WHOI)的研究人员希望能够更好地定量和机理地了解EDW中的二氧化碳动态。这项工作利用了2006-2007年的实地计划，以及NSF赞助的实地项目气候模式水动力学实验(CLIMODE)将获得的对EDW物理的更好理解。CarboMODE提出的主要问题是“海洋对北大西洋EDW中二氧化碳的吸收和归宿是什么？”根据这一一般性问题，提出了更具体的问题，包括：(1)冬季EDW形成期间的海-气CO2通量是什么？(2)垂直/横向混合、平流/搅拌、(3)当EDW俯冲(注入)到副热带气旋时，EDW中溶解无机碳(DIC)的含量是多少？(4)EDW的形成如何影响北大西洋副热带气旋中的次表层无机碳库和大气-海洋CO2通量？(5)EDW中无机碳的去向如何？次表层再矿化作用如何影响EDW中DIC的含量？为了解决这些问题，研究人员建议在2007年收集无机碳数据，作为CLIMODE项目的一部分。他们对CLIMODE(和CarboMODE)项目的贡献将是DIC、总碱度(TA)和在航二氧化碳(即海水和空气中的二氧化碳)的测量。尽管CLIMODE的问题和假设侧重于物理学，但CLIMODE的问题和假设框架下的观测和模拟计划恰好提供了一个及时和独特的机会来解决所提出的关于二氧化碳动力学(以及与养分和溶解氧动力学有关的问题)的问题。综合和模拟若干不同的数据集，包括2007年CLIMODE对EDW的实地调查，从2006年CLIMODE邮轮收集的二氧化碳数据，BATS百慕大-波多黎各年度样带向北延伸4天的数据，以及每周两次从志愿观察船MV Oleander(由美国国家海洋和大气层管理局COSP资助)收集的EDW形成区域表层海水PCO2(以及DIC和碱度)数据，构成解决有关CarboMODE问题的核心。在更广泛的影响方面，这项研究将提供有关海洋二氧化碳汇进入北大西洋EDW层的基本数据，并将有助于在各种科学计划和实施结构(例如，NACP、CCSP、OCCC、SOLAR-IMBER)下协调的碳循环研究，旨在建立对海洋二氧化碳来源和汇的准确估计，以及调节它的基本机制。该项目将支持BBSR的一名全日制博士后研究员。这项研究的科学理解和研究成果将用于BBSR的本科生和研究生教育活动，并有助于两名研究技术人员和一名世界卫生组织本科生的研究和技术技能。

The formation of mode waters, like Eighteen Degree Water (EDW) in the North Atlantic Ocean, is important for driving ocean circulation, ventilating and transferring biogeochemical properties to the ocean interior. Recent studies suggest that EDW plays an important role in setting the nutrient reservoir of the subtropical gyre [Jenkins and Doney, 2003; Doney and Jenkins, 2004; Palter et al., 2005], with significant implications for nutrient and carbon dynamics, and productivity in the subtropical gyre of the North Atlantic. In addition, EDW has a potentially important role in the ocean uptake and decadal variability of atmospheric CO2 [Bates et al., 2002]. In this study, researchers at the Bermuda Biological Station for Research (BBSR) and the Woods Hole Oceanographic Institution (WHOI) hope to achieve a better quantitative and mechanistic understanding of the CO2 dynamics in EDW. The work leverages the 2006-2007 field program and improved understanding about the physics of EDW that an NSF sponsored field project, CLImate MOde water Dynamics Experiment (CLIMODE) will gain. The main question posed in CarboMODE is "What is the oceanic uptake and fate of CO2 in EDW in the North Atlantic Ocean?" From this general question, more specific questions are raised, including: (1) What is the air-sea CO2 flux during wintertime EDW formation? (2) What are the relative contributions from vertical/lateral mixing, advection/stirring, air-sea CO2 gas exchange and biological depletion of CO2 due to net community production during EDW formation that influence the DIC properties of EDW? (3) What is the dissolved inorganic carbon (DIC) content of EDW upon subduction (injection) into the subtropical gyre and what is the overall flux? (4) How does the formation of EDW impact the subsurface inorganic carbon reservoir and air-sea CO2 fluxes in the subtropical gyre of the North Atlantic Ocean? (5) What is the fate of inorganic carbon in EDW as it advects away from the region of formation and how does subsurface remineralization contribute to the DIC content of EDW? In addressing these questions, the investigators propose will collect inorganic carbon data in 2007 as part of the CLIMODE project. Their contribution to the CLIMODE (and CarboMODE) project will be measurements of DIC, Total Alkalinity (TA) and underway pCO2 (i.e., seawater and air pCO2). Although focused on physics, the observational and modeling program framed by CLIMODE's questions and hypotheses fortuitously provide a timely and unique opportunity to address questions raised about CO2 dynamics (and related issues concerning nutrient and dissolved oxygen dynamics). Synthesis and modeling of several different datasets, including the 2007 CLIMODE field surveys of EDW, CO2 data collected from a 2006 CLIMODE cruise, a 4 day northward extension of the BATS Bermuda-Puerto Rico annual transect, and surface seawater pCO2 (and DIC and alkalinity) data collected twice a week in the region of EDW formation from the Volunteer Observing Ship (VOS) MV Oleander (funded by NOAA COSP), form the nucleus for addressing relevant CarboMODE questions. In terms of broader impacts, this study will provide fundamental data on the oceanic sink of CO2 into North Atlantic EDW layer and will contribute to carbon cycle studies coordinated under a variety of science programs and implementation structures (e.g., NACP, CCSP, OCCC, SOLAR-IMBER) that aim to establish accurate estimates of oceanic CO2 sources and sinks, and the underlying mechanisms that regulate it. The project will support one full time post-doctoral fellow at BBSR. Scientific understanding and research products from the research will be used in undergraduate and graduate educational activities at BBSR, and contribute to the research and technical skills of two research technicians, and one undergraduate student from WHOI.