Collaborative Research: Autonomous eddy covariance air-sea CO2 flux system for moored buoys

准确预测大气和海洋之间的二氧化碳交换是地球系统模型的重要要求，但最先进的气候模型中的交换估计仍然不确定。需要改进的一个模型因素是跨海气界面的气体转移速率，而微气象涡旋协方差(EC)通量技术可以提供改进和验证广泛风浪条件下的转移速率模型所需的现场测量结果。虽然EC技术在陆地上被广泛采用，但几个技术障碍阻碍了在海上，特别是在无人值守的浮动平台上更广泛地采用这种方法收集二氧化碳通量数据。该团队最近的工作表明，作为EC技术的核心，快速响应的闭路二氧化碳传感器可以进行修改，以显著减少由于船舶和浮标运动影响而产生的二氧化碳误差。根据这一新计划，该团队将进一步改进这些传感器，并采用用于更大的舰载二氧化碳通量系统的方法，以开发适合于越来越多的自主海洋观测平台的小型、坚固、准确和低功耗的系统。该项目的目标是1)设计、建造和现场展示新一代红外气体分析仪，其设计旨在有效地消除困扰先前海-气交换野外实验的运动干扰，以及2)建立和部署一个紧凑的端到端涡动协方差二氧化碳通量系统，适合在所有天气条件下和在必须最大限度减少功率需求的小型海洋观测平台上进行自主测量。近海浮标现场演示将在缅因湾的一个长期二氧化碳测量点附近进行，在那里，支持海洋和气象观测将提供传感器和系统评估和验证所需的数据。这项工作将使用与工业界、学术界和海洋观测系统工程师正式合作的团队方法来执行。该项目最终的基于浮标的通量测量系统将与NSF OOI合作设计，以促进与现有和未来海洋观测平台的集成，为扩大海上直接协方差二氧化碳通量测量铺平道路，以支持广泛的碳循环和海气相互作用研究和应用。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Accurate prediction of carbon dioxide exchange between the atmosphere and oceans is an important earth system model requirement, but the exchange estimates in state-of-the-art climate models remain uncertain. One model factor that requires improvement is the rate of gas transfer across the air-sea interface, and the micrometeorological eddy covariance (EC) flux technique can provide field measurements needed to improve and validate transfer rate models across a broad range of wind and wave conditions. While the EC technique is widely employed on land, several technical hurdles have hindered wider adoption of this approach for CO2 flux data collection at sea, particularly on unattended floating platforms. Recent work by this team has demonstrated that fast-response closed-path CO2 sensors, central to the EC technique, can be modified to substantially reduce CO2 error due to ship and buoy motion effects. Under this new program, the team will further improve these sensors and also adapt approaches used for larger shipboard CO2 flux systems to develop a small, robust, accurate, and low power system suitable for use on a growing number of autonomous ocean observing platforms. The goals of this project are to 1) design, build and field-demonstrate a next generation infrared gas analyzer engineered to effectively remove motion interference that has plagued previous air-sea gas exchange field experiments, and 2) build and deploy a compact end-to-end eddy covariance CO2 flux system suitable for autonomous measurements through all weather conditions and on small ocean observing platforms where power demands must be minimized. Offshore buoy field demonstrations will be conducted near a long-term CO2 measurement site in the Gulf of Maine where supporting ocean and meteorological observations will provide data needed for sensor and system assessment and validation. The work will be performed using a team approach that formally partners industry, academia, and ocean observing system engineers. The project's final buoy-based flux measurement system will be designed in collaboration with NSF OOI to facilitate integration onto existing and future ocean observing platforms, paving a way for expanded at-sea direct covariance CO2 flux measurements to support a broad range of carbon cycle and air-sea interaction studies and applications.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.