[A-OS21] Global ocean observation networks: Current status, results, re-assessments, and future perspectives

[AOS21-01] OneArgo: Its Background, Significance, and Challenges

*Toshio Suga^1,2 (1.Graduate School of Science, Tohoku University, 2.JAMSTEC)

Keywords:Argo, BGC Argo, Deep Argo, GOOS, UN Ocean Decade

OneArgo is a program to transform the Core Argo array of profiling floats, which measures temperature and salinity in the upper 2000m of the open ocean, into one that has truly global reach, including the polar oceans and marginal seas, extending to the full ocean depth and including ocean biogeochemical (BGC) measurements. It is also the name of the resulting observation network. To be more precise, OneArgo is a program that integrates the following three missions: (1) the expansion of Core Argo to include higher latitudes than 60 degrees north-south (including seasonal ice zones) and the marginal seas, which were not targeted at the beginning of the original Argo, and to double the float density in the tropics and near the western boundary currents; (2) Deep Argo to measure temperature and salinity from the sea surface to the seafloor; and (3) BGC Argo to measure six BGC variables (oxygen, nitrate, pH, chlorophyll-a, suspended particles, and downward irradiance). The three missions will share a powerful data system that will deliver automated quality-controlled data in near real-time and deliver highly quality-controlled data after a certain period of time. More importantly, both Deep Argo and BGC Argo floats will be responsible for the Core mission, i.e., the once-every-10-days observation of temperature and salinity at the top 2000 meters, and will contribute to the expansion of the Core Argo observation network. In other words, OneArgo does not simply add Core Argo, Deep Argo, and BGC Argo together but integrates them to build a fully integrated observation network.

OneArgo will be seamlessly integrated with satellite observations and other in-situ observation networks of the Global Ocean Observing System, such as GO-SHIP, contributing to operational reanalysis and improved forecasting capabilities, and enabling assessment of the state and variability of the climate system with respect to physical, biogeochemical, and ecological parameters. It is also expected to enable basic research of an unprecedented range and magnitude.

Why OneArgo? The reason is obvious: it is much more economical than building and operating three separate observation networks. In terms of cost, OneArgo was the only choice to realize the three missions of Core, Deep, and BGC. However, even if built efficiently as a single unit, OneArgo is estimated to cost three times as much to maintain as the existing Core Argo, and no budget has been secured for OneArgo's construction, much less a sustainable source of funding. In addition, the construction and maintenance of the observation network while balancing the missions requires much more complex coordination than Core Argo. In addition, the complexity of the data system and the significant increase in the workload are major issues to be addressed. In this presentation, we will discuss how OneArgo is trying to tackle these issues.