Collaborative Research: Carbon Flux Through the Twilight Zone - New Tools to Measure Change

海洋中碳分布的变化是由物理化学和生物过程共同作用引起的。溶解度泵通过高纬度地区的冷水下沉将碳注入深海，在那里二氧化碳的溶解度增强。海洋生物泵在空间和时间上具有高度动态性和可变性。这一过程包括海洋表层生物产生有机碳，随后将这种物质封存在冬季混合层之下。在了解生物泵的控制方面已经付出了巨大的努力，虽然了解了其一般功能，但细节仍然难以捉摸。目前，人们对地表光亮带的过程的了解要比暗晕带（即中深辉带）的过程了解得多。在人们知之甚少的“暮光地带”内，下沉颗粒上的碳衰减和下沉物质的组成发生了变化，这对海洋表面与大气的碳吸收和交换速率以及深海中较长期的碳固存产生了重要影响。该提案将开发改进的粒子通量收集器，并使用这些收集器来回答与百慕大大西洋时间序列研究（BATS）站点的C通量和沉降粒子交换相关的关键科学问题。目前在BATS，表层海洋C预算是不平衡的，生产和群落结构无法预测颗粒出口。与此同时，这些问题正在用一种不完美的工具来解决，即漂流沉积物陷阱，这种装置自20世纪80年代初以来就没有发生过重大变化。该计划包括新工具的开发和工程，同时收集时间序列数据。该项目建立在最近开发的中性浮力沉积物捕集器（NBST）的基础上，该捕集器将被修改为连续通量收集和游泳者免费样本的新设计：Twilight Zone EXplorer （TZEX）。在地球系统碳和水计划背景下，本提案通过结合以下多学科要素来推进我们对碳循环的理解：(1)通过船舶观测和遥感获得的海洋生物学基础研究；(2)颗粒和水的地球化学特征及其随深度和时间的变化；(3)流动流体中生物过程和粒子输运的建模；(4)新型沉降粒子观测设备的设计与应用。这些独特的沉积物捕获装置将为评估海洋作为碳汇的作用以及海洋出口生产将如何响应气候变化打开一扇新的窗口。更广泛的影响：通过提高对中上层过渡带碳循环的认识，该项目将有助于提高社会预测全球气候变化影响的能力，并制定补救策略。教育和公共宣传影响包括为高中生、本科生和研究生、记者、一名本科生研究员和两名研究生提供泊位。最后，重要的仪器开发和应用组件可能会为更广泛的海洋学社区带来重大成果。

Changes in the distribution of carbon within the ocean are caused by a combination of physicochemical and biological processes. The solubility pump injects carbon into the deep sea through the sinking of cold waters at high latitudes where CO2 solubility is enhanced. The oceanic biological pump is highly dynamic and variable in space and time. This process consists in the production of organic carbon by organisms in the surface ocean and the subsequent sequestration of this material below the winter mixed layer. Significant effort has gone into understanding the controls of the biological pump and while the general function is understood, the details remain elusive. At present, processes in the surface euphotic zone are much better understood than those of the Twilight Zone (i.e. mesopelagic). It is within the poorly understood Twilight Zone that changes in C attenuation on sinking particles and the composition of sinking material occur, with important consequences for the rates of C uptake and exchange at the surface ocean with the atmosphere and for longer term C sequestration in the deep sea.This proposal will develop improved particle flux collectors and use these to answer key science questions associated with C fluxes and exchange via sinking particles at the Bermuda Atlantic Time-series Study (BATS) site. Currently at BATS, the surface ocean C budgets are unbalanced, and production and community structure fail to predict particle export. At the same time, these questions are being addressed with an imperfect tool, the drifting sediment trap, a device that has not changed significantly since the early 1980's. This program includes the development and engineering of new tools while collecting time-series data. The project builds upon the recently developed neutrally buoyant sediment trap (NBST), which will be modified for continuous flux collection and swimmer free samples to a new design: the Twilight Zone EXplorer (TZEX).In context of the C and Water in the Earth System Program, this proposal advances our understanding of the carbon cycle by combining the following multidisciplinary elements: (1) basic research in ocean biology obtained from ship based observations and remote sensing; (2) geochemistry of particles and waters and how these change with depth and time; (3) modeling of biological processes and particle transport in moving fluids; and (4) the engineering and application of novel observational equipment to capture sinking particles. These unique sediment trap devices will open up a new window to assess the ocean's role as a C sink and how marine export production will change in response to climate change.Broader Impacts: By improving understanding of the carbon cycle in the mesopelagic twilight zone, this project will contribute to society's ability to anticipate the impacts of global climate change as well as to formulate remediation strategies. Educational and public outreach impact include berth space for high school, undergraduate and graduate students, journalists, an undergraduate student fellow and two graduate students. Finally, the significant instrumentation development and application component will likely bear significant fruit for the broader oceanographic community.