Collaborative Research: Improving the accuracy and uncertainty associated with estimated pCO2 from pH sensors on autonomous profiling platforms

协作研究：提高自主分析平台上 pH 传感器估计 pCO2 的准确性和不确定性

• 批准号: 2048509
• 负责人: Brendan Carter
• 金额: $ 10.97万
• 依托单位: University of Washington
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-06-01 至 2024-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2048509&HistoricalAwards=false
• 关键词: Collaborative; Research; Improving; accuracy; uncertainty

Understanding how much anthropogenic carbon dioxide the ocean is taking up from the atmosphere - and how this uptake changes over time - is critical for understanding the habitability of our planet. Uncertainties in the size of the ocean carbon sink remain large, mainly because of sparse measurements of surface water carbon dioxide (pCO2) measurements from ships. Profiling floats equipped with sensors for biogeochemical (BGC) measurements such as pH – which can be used to estimate pCO2 – have the potential to greatly improve the amount of surface carbon dioxide observations across the world’s ocean, particularly in regions and times of year where shipboard measurements are scarce. The number of BGC floats deployed worldwide is expected to rapidly increase in the coming years through programs like the Global Ocean Biogeochemistry Array (GO-BGC) and the Southern Ocean Carbon and Climate Observations and Modeling program (SOCCOM2). However, there are still fundamental issues that need to be resolved before we can take full advantage of this emerging, powerful global observational network to improve our estimates of how much anthropogenic carbon the ocean absorbs every year. The overarching aim of this project is to improve the accuracy and precision of pCO2 estimates that are derived from profiling float data. The project will support a postdoctoral researcher and three undergraduate summer interns.This project seeks to improve the accuracy and uncertainty associated with float-based estimates of pCO2 by addressing the outstanding questions and issues that could lead to systematic biases in these calculations. Specifically, the investigators aim to answer the following questions: 1) What causes the pressure-dependent discrepancy between bottle and float pH? 2) What is the source of the internal inconsistency of the thermodynamic marine inorganic carbon model, which affects the accuracy of pCO2 computed from pH measurements? 3) What are the global spatiotemporal patterns of acidification rate at 1500 m, and how do we model the patterns accurately? The team will conduct a series of laboratory studies to quantify key thermodynamic constants, test the hypothesis that organic compounds are a substantial contributor for the internal inconsistency, and determine a robust protocol to accurately calculate pCO2 from pH. Furthermore, an open-source, global algorithm will be made available that accurately predicts region-specific anthropogenic carbon estimates, which is necessary to accurately correct float pH sensor drift globally. Finally, to assess the improvement in accuracy of float based pCO2 estimates based on these efforts, the team will conduct a series of field validation experiments using Spray underwater gliders equipped with the same pH sensor as profiling floats, and a Wave Glider, an autonomous surface vehicle that is equipped with a pCO2 analyzer calibrated with gas standards with an accuracy of plus or minus two microatmospheres. Over the course of the project, the team will test 16 different pH sensors to better constrain the potential systematic biases for the float based pCO2 estimates. The activities outlined here will lead to more accurate estimates of pCO2 from floats, as well as better constrained uncertainties, and ultimately lead to better estimates for air-sea CO2 flux from the global network of BGC profiling floats.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.

了解海洋从大气中吸收了多少人为二氧化碳，以及这种吸收如何随时间变化，对于了解我们星球的可居住性至关重要。海洋碳汇规模的不确定性仍然很大，主要是因为船舶对地表水二氧化碳（pCO2）的测量很少。配备了生物地球化学（BGC）测量传感器（如pH值）的剖面浮标（可用于估计二氧化碳分压）有可能大大提高全球海洋表面二氧化碳的观测量，特别是在船上测量稀缺的地区和一年中的时间。通过全球海洋生物地球化学阵列（GO-BGC）和南大洋碳和气候观测与建模计划（SOCCOM2）等项目，预计未来几年全球部署的BGC浮标数量将迅速增加。然而，在我们充分利用这个新兴的、强大的全球观测网络来改进我们对海洋每年吸收多少人为碳的估计之前，仍有一些基本问题需要解决。该项目的总体目标是提高从剖面浮子数据中得出的二氧化碳分压估计的准确性和精度。该项目将支持1名博士后研究员和3名本科生暑期实习生。该项目旨在通过解决这些计算中可能导致系统偏差的突出问题和问题，提高基于浮子的二氧化碳分压估算的准确性和不确定性。具体来说，研究人员的目标是回答以下问题：1)是什么原因导致瓶和浮子pH值之间的压力依赖性差异？2)热力学海洋无机碳模型内部不一致的根源是什么，从而影响了由pH测量计算的pCO2的准确性？3)全球1500 m酸化速率的时空格局是什么？我们如何准确地模拟这些格局？该团队将进行一系列的实验室研究，以量化关键的热力学常数，测试有机化合物是内部不一致的重要贡献者的假设，并确定一个可靠的协议，以准确地从pH值计算二氧化碳分碳。此外，将提供一个开源的全球算法，以准确预测区域特定的人为碳估计，这是准确纠正浮动pH传感器全球漂移所必需的。最后，为了评估基于浮子的pCO2估算精度的提高，该团队将进行一系列现场验证实验，使用配备与分析浮子相同的pH传感器的Spray水下滑翔机和Wave Glider，这是一种自动水面车辆，配备用气体标准校准的pCO2分析仪，精度为正负两个微大气压。在整个项目过程中，研究小组将测试16种不同的pH传感器，以更好地限制浮子估算二氧化碳分压的潜在系统偏差。本文概述的活动将使我们能够更准确地估计浮子的二氧化碳分压，以及更好地约束不确定性，并最终使我们能够更好地估计BGC剖面浮子全球网络的海气二氧化碳通量。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

项目成果

New and updated global empirical seawater property estimation routines

新的和更新的全球经验海水特性估计例程

• DOI: 10.1002/lom3.10461
• 发表时间: 2021
• 期刊: Limnology and Oceanography: Methods
• 作者: Carter, Brendan R.;Bittig, Henry C.;Fassbender, Andrea J.;Sharp, Jonathan D.;Takeshita, Yuichiro;Xu, Yuan‐Yuan;Álvarez, Marta;Wanninkhof, Rik;Feely, Richard A.;Barbero, Leticia
• 通讯作者: Barbero, Leticia