Argo Data 1999–2019: Two Million Temperature-Salinity Profiles and Subsurface Velocity Observations From a Global Array of Profiling Floats

Annie P S Wong,Andrea Garcia Juan,Nathalie Verbrugge,Gregory C Johnson,Giulio Notarstefano,Jon Turton,E Pattabhi Rama Rao,Stephen C Riser,Igor Yashayaev,Mathieu Belbéoch,Toshio Suga,David J Murphy,Paul M Barker,Yasushi Takatsuki,Eitarou Oka,Shigeki Hosoda,Hervé Claustre,Tetjana Ross,Taiyo Kobayashi,Ingrid M Angel-Benavides,Cécile Cabanes,Matthew Donnelly,Dean Roemmich,W Brechner Owens,Noé Poffa,M Ravichandran,Peter R Oke,Serge Le Reste,Mingmei Dong,Naoto Iwasaska,Christine Coatanoan,T V S Udaya Bhaskar,Mary Mowat,Thierry Carval,Carole Saout-Grit,Tomoaki Nakamura,John M Lyman,Megan Scanderbeg,Denis Gilbert,Vincent Bernard,Bernard Bourlès,Birgit Klein,Kanako Sato,Claudia Schmid,Zenghong Liu,Sabrina Speich,Romain Cancouët,Isabelle Gaboury,Sarah G Purkey,Howard J Freeland,Matthew B Alkire,Sylvie Pouliquen,Cora Hersh,Rebecca Cowley,Delphine Dobbler,Nathalie Zilberman,Takashi Yoshida,Fiona Carse,Katie Gowers,Mark Ignaszewski,Anh Tran,Nicolas Kolodziejczyk,Xavier André,Mathieu Ouellet,Guillaume Maze,Shuhei Masuda,Steven R Jayne,Virginie Thierry,John Gilson,Katsunari Sato,Frank Bahr,Pierre‐Yves Le Traon ,Jenny Lovell ,Pierre‐Marie Poulain ,Molly O’neil Baringer ,Fabrizio D’ortenzio ,Justin Buck ,Hyeong Jun Jo ,Susan Wijffels ,Shigeaki Yoshida ,K E Mctaggart ,Dana D Swift ,S Guinehut ,Paul E Robbins ,Frédéric Merceur ,Philip Sutton ,S G Loch ,Jérôme Gourrion ,Sung Dae Kim ,Kenji Ando ,Jean Philippe Rannou ,Kim I Martini ,W.j Gould ,Esmee Van Wijk ,D E West-Mack ,P Vélez‐Belchí ,Ki Ryong Kang ,B J W Greenan ,Jing Xu ,Brian King ,Hyuk Min Park

doi:10.3389/fmars.2020.00700

Abstract

In the past two decades, the Argo Program has collected, processed and distributed over two million vertical profiles of temperature and salinity from the upper two kilometers of the global ocean. A similar number of subsurface velocity observations near 1000 dbar have also been collected. This paper recounts the history of the global Argo Program, from its aspiration arising out of the World Ocean Circulation Experiment, to the development and implementation of its instrumentation and telecommunication systems, and the various technical problems encountered. We describe the Argo data system and its quality control procedures, and the gradual changes in the vertical resolution and spatial coverage of Argo data from 1999 to 2019. The accuracies of the float data have been assessed by comparison with high-quality shipboard measurements, and are concluded to be 0.002°C for temperature, 2.4 dbar for pressure, and 0.01 PSS-78 for salinity, after delayed-mode adjustments. Finally, the challenges faced by the vision of an expanding Argo Program beyond 2020 are discussed.

Highlights

Prior to the turn of the 21st century, comprehensive in-situ ocean observations were difficult to obtain
This paper describes the pressure (P), temperature (T), salinity (S), and subsurface velocity data from the Argo Program: the instrumentation used, the technical problems encountered, the scientific quality of the data, the data distribution system, and how the dataset has evolved in response to new technologies
In Argo delayed-mode salinity analysis, two separate reference databases are used: a first one that is based on shipboard CTD data, and a second one that is based on Argo profiles that have been judged as accurate and needing no adjustment

Summary

INTRODUCTION

Prior to the turn of the 21st century, comprehensive in-situ ocean observations were difficult to obtain. Since 2019, a daily MIN-MAX test (Gourrion et al, 2020) has been implemented at Coriolis to compare float profiles with a climatology of minimum and maximum values computed from Argo delayed-mode data and high-quality CTD data This aids in the identification of sensor drift at an early stage. In Argo delayed-mode salinity analysis, two separate reference databases are used: a first one that is based on shipboard CTD data, and a second one that is based on Argo profiles that have been judged as accurate and needing no adjustment Both databases are updated periodically to include more recentlyacquired reference data, so as to account for temporal changes in the global ocean. Analysis of delayed-mode salinity data from 10,048 Argo floats showed that for the first 2 years after deployment (about 72 cycles), < 10% of the floats required any kind of sensor drift adjustment (Figure 10). Advances in ML algorithms should provide an important resource to the Argo community to help to meet the challenge of maintaining the quality of its data from ever more floats and diversified missions

DISCUSSION AND CONCLUSION

Findings

DATA AVAILABILITY STATEMENT