Net Biological Oxygen Production Using O2 Measurements on Argo Floats

现在，通过提高现场氧气测量的质量，可以设想在全球范围内精确测量海洋2000米以上氧气浓度的季节性变化。目前，这些测量可以通过浮子、系泊和滑翔机进行远程测量。对迄今为止从Argo浮标上的氧气传感器返回的数据进行的分析表明，这些测量的准确性目前不足以解决空气-海洋氧气交换和温跃层中十年尺度的氧气变化缓慢的紧迫问题。然而，最近在系泊和滑翔机上进行的氧气测量工作表明，如果建立了校准协议，使用可用传感器确定氧气浓度的精度可能高于+/- 0.5%，这足以解决这些问题。在这个项目中，华盛顿大学的研究人员希望在西北太平洋黑潮延伸区这一具有海洋战略意义的位置，在浮子部署之前和部署期间，使用基于浮子的Aanderaa Optode传感器来证明这一点。这是一个由物理和生物过程共同作用造成的冬季二氧化碳分压下降剧烈的区域。该团队将通过在浮子和该地区的地面系泊上测定的氧气数据来确定净生物氧气产量，从而评估生物过程在创建碳汇中的相对重要性。因此，该项目有两个主要目标：(1)测试必要的程序，以提高剖面浮子上原位氧气测量的准确性，以便制定未来扩展氧气传感器部署的协议；(2)确定生物生产在控制西北太平洋表层二氧化碳浓度冬季急剧下降中的作用。该团队将在黑潮延伸地区部署10个带有氧气传感器的Argo浮标（由Argo公司出资建造）。氧气传感器和气体张力装置也将部署在该地区现有的地面系泊上，以获得更详细的数据时间序列，与浮子测量结果进行比较。氧气传感器将在部署前在实验室进行校准，并在部署后在海洋中进行现场校准，将其输出与温克勒滴定法的测量结果进行比较。这些浮子将被编程，当它们浮出水面时在大气中进行测量，并通过卫星将数据传输到岸上，作为现场校准的一种手段。有了这种校准冗余，他们将能够确定所需的方案，以在更广泛的范围内获得准确的原位O2数据，而不需要大量的校准。更广泛的影响。对海洋研究界的更广泛影响包括制定O2传感器校准协议，以便在自主平台上更广泛地就地使用。对教育更广泛的影响包括华盛顿大学研究船RV T.G.汤普森的“学生巡航”。该邮轮将为10-15名本科生提供实地海洋学和海洋研究的机会，同时完成他们本科海洋学学位所需的顶点研究。华盛顿大学已经承诺了12天的船上时间来适应这项研究的教育方面。

It is now possible to envision global-scale measurements of accurate, seasonal variations of oxygen concentrations in the upper 2000 meters of the ocean by improving the quality of in situ oxygen measurements. These measurements can presently be made remotely by floats, moorings, and gliders. Analysis of data returned so far from oxygen sensors on Argo floats indicates that accuracy of these measurements is presently not sufficient to solve the pressing problems of air-sea oxygen exchange and slow decadal-scale O2 change in the thermocline. However, recent work with oxygen measurements on moorings and gliders suggest that it is possible to determine oxygen concentrations using available sensors to better than +/- 0.5 % accuracy if calibration protocols are established, which would be sufficient to address these problems. In this project, researchers at the University of Washington hope to demonstrate this using float-based Aanderaa Optode sensors calibrated before and during float deployment in a location of strategic oceanographic interest -- the Northwest Pacific Kuroshio Extension. This is a region of intense pCO2 draw down in winter caused by a combination of physical and biological processes. The team will evaluate the relative importance of biological processes in creating the carbon sink by determining the net biological oxygen production from O2 data determined on floats and on a surface mooring in the area. The project thus has two main goals: (1) to test the procedures necessary to improve accuracy of in situ oxygen measurements on profiling floats so that a protocol for future expansion of O2 sensor deployment can be developed; and (2) to determine the role of biological production in controlling the dramatic wintertime draw-down of surface ocean pCO2 in the Northwest Pacific Ocean. The team will deploy 10 Argo floats (constructed at Argo expense) with oxygen sensors in the Kuroshio Extension region. An oxygen sensor and gas tension device will also be deployed on an existing surface mooring in the region to derive a much more detailed data time series to compare with the float measurements. The oxygen sensors will be calibrated both in the laboratory before deployment and in situ in the ocean after deployment by comparing their output to measurements by Winkler titration. The floats will be programmed to make measurements in the atmosphere when they surface to transmit data to shore via satellite as a means of in situ calibration. With this calibration redundancy they will be able to determine the protocol necessary to achieve accurate in situ O2 data on a much broader scale with less extensive calibration. Broader Impacts. Broader impacts to the marine research community include development of a protocol for calibration of O2 sensors so they can be used more broadly in situ on autonomous platforms. Broader impacts to education involve a "student cruise" on the University of Washington research vessel RV T.G. Thompson. This cruise will expose 10-15 undergraduate students to the experience of field oceanography and marine research, while fulfilling their required capstone research for the undergraduate oceanography degree. The University of Washington has committed twelve days of the ship time to accommodate the educational aspects of the study.