Calibrated pCO2 in air and surface ocean Sensor for ASVs (CaPASOS)

在可预见的未来，人类排放的二氧化碳(主要来自化石燃料燃烧)将继续成为气候变化的最重要原因。然而，只有大约一半的排放留在了大气中。据信，另一半被陆地上的植被和海洋吸收的数量大致相同。因此，这些二氧化碳的“自然汇”对我们来说具有巨大的价值，因为它们减缓了气候变化的进程，因此它们目前的运行以及未来可能发生的二氧化碳吸收变化，是密集研究的重点。今天，通过测量大气和海面的二氧化碳分压，可以观察到二氧化碳流入海洋的过程。它控制着海洋和大气之间二氧化碳交换的速率，因此被全球海洋观测系统指定为“基本海洋变量”。这些观测通常是从商业船只上进行的，在有繁忙的航运路线的地方，例如在大西洋和北太平洋的大部分地区，有足够的观测来描述海-气通量。然而，还有其他非常大的地区(例如印度洋、南太平洋和南大洋)，我们的数据严重不足。未来，这种需求可以通过自主水面车辆(ASV)进行二氧化碳测量来满足，我们的建议是开发一种专门为ASV设计的PCO2传感器。它将遵循国际机构为最高质量的测量制定的协议，这些测量适合计算公海二氧化碳的海气通量。技术挑战是调整安装在船上或大型浮标上的仪器的成功原理，在空间和功率不是限制因素的情况下，实现ASV所需的空间和功率占用小、抗剧烈运动和耐久的同样高的精度。我们将通过将埃克塞特大学集团20多年来在运营船舶二氧化碳系统方面的丰富经验与工程改进结合起来，利用NOC技术和工程小组的经验和专业知识来实现这一目标。我们将使用在大型仪器上经过良好测试的基本测量技术(水与气体的平衡，以及非色散红外探测测量气体中的二氧化碳)。然而，我们将使用体积小、气体流速低的微型部件，使即使是小型仪器也能携带机载校准气体。最终仪器的规格将包括：耐用性长达一年，测量频率(地表水和大气)足以确定每日循环，使用储存在微型压缩气瓶中的机载校准气体进行定期校准，以及测量通过直接接触与地表水平衡的干燥空气中的二氧化碳。该仪器还将符合数据标准和集成协议，以使传感器能够随时集成和交换到自主平台。为了实现我们的主要目标，我们的次级目标是：1)开发第二代系统，并与船用仪器一起部署，以及在沿海地点进行测试(2)在西海峡天文台的系泊设备上进行改装和较长时间的部署；(3)建造第三代系统，注重系统的每个组成部分，以优化性能和稳固性；(4)整合到ASV中；(5)广泛的海上测试(例如，“MASSMO”演习、在英国水域附近定期进行的自动海上车辆实验任务以及在研究巡航上)。

The human emission of carbon dioxide, largely from fossil fuel burning, will continue for the foreseeable future to be the most important cause of climate change. Only about half of our emissions are remaining in the atmosphere however. The other half is being absorbed, it is believed, in approximately equal amounts by vegetation on land and uptake by the ocean. These "natural sinks" of CO2 are consequently of huge value to us, since they slow the progress of climate change, so their present operation, and possible changes future uptake of CO2, are a focus of intense research. The sink of CO2 into the ocean is today being observed by measurements of atmospheric and sea surface pCO2, the partial pressure of CO2 at the surface of the ocean. This controls the rate at which CO2 exchanges between the ocean and atmosphere, and which for this reason has been designated an "essential ocean variable" by the Global Ocean Observing System. These observations are usually made from commercial vessels, and where there are busy shipping routes, for example in much of the Atlantic and North Pacific Oceans, there are sufficient observations to describe the air-sea flux. However, there are other very large regions (the Indian, South Pacific and Southern Oceans for example) where we have woefully insufficient data. In the future, this need could be met by autonomous surface vehicles (ASVs) making pCO2 measurements, and our proposal is to develop a pCO2 sensor specifically designed for ASVs. It will follow protocols that have been established by international bodies for the highest quality measurements suited to calculating the air-sea flux of carbon dioxide in the open ocean. The technical challenge is to adapt the successful principles of the instruments mounted in ships or on large buoys, where space and power are not limiting factors, to achieve the same high accuracy with small space and power footprint, resistance to violent motion, and long endurance, necessary on an ASV. We will achieve this by bringing together the extensive experience that the Exeter University group has in operating ship-based CO2 systems over 20 years, with improvements in engineering, utilising the experience and expertise of the NOC Technology and Engineering groups. We will use the basic measurement technique that has been well tested on the large instruments (equiibration of water with gas, and measurement of CO2 in gas by non-dispersive infra-red detection). However, we will use miniaturised components having small volumes and low flow rates of gas, enabling even a small instrument to carry on-board calibration gases. The specifications of the final instrument will include: endurance of up to a year and with frequency of measurements (both surface water and atmosphere) sufficient to define daily cycles, regular calibration using on-board calibration gases stored in miniature compressed gas cylinders, and measurement of CO2 in dried air which has equilibrated with surface water by direct contact. The instrument will also conform to data standards and integration protocols to enable the ready integration and exchange of sensors into autonomous platforms.A laboratory prototype exists, built by U. Exeter. To achieve our main objective, our sub-objectives are: 1) Development of second generation and deployment alongside a shipboard instrument and testing at coastal sites (2) modification and deployment on a mooring at the Western Channel Observatory for an extended period (3) Construction of third generation with attention to each component of the system to optimise performance and robustness, (4) integration into an ASV, (5) extensive sea testing (e.g. on the "MASSMO" exercises, experimental missions of autonomous marine vehicles conducted regularly around UK waters, and on research cruises.