A BGC-Argo Guide: Planning, Deployment, Data Handling and Usage

Abstract

The Biogeochemical-Argo program (BGC-Argo) is a new profiling-float-based, ocean wide, and distributed ocean monitoring program which is tightly linked to, and has benefited significantly from, the Argo program. The community has recommended for BGC-Argo to measure six additional properties in addition to pressure, temperature and salinity measured by Argo, to include oxygen, pH, nitrate, downwelling light, chlorophyll fluorescence and the optical backscattering coefficient. The purpose of this addition is to enable the monitoring of ocean biogeochemistry and health, and in particular, monitor major processes such as ocean deoxygenation, acidification and warming and their effect on phytoplankton, the main source of energy of marine ecosystems. Here we describe the salient issues associated with the operation of the BGC-Argo network, with information useful for those interested in deploying floats and using the data they produce. The topics include float testing, deployment and increasingly, recovery. Aspects of data management, processing and quality control are covered as well as specific issues associated with each of the six BGC-Argo sensors. In particular, it is recommended that water samples be collected during float deployment to be used for validation of sensor output.

A Regional Neural Network Approach to Estimate Water-Column Nutrient Concentrations and Carbonate System Variables in the Mediterranean Sea: CANYON-MED

“…Some variables are presently almost systematically measured regardless of the acquisition platform, for instance physical data (temperature, salinity, pressure) and dissolved oxygen concentration (O 2 ). However, measurements from these autonomous platforms remain limited to a small type of biogeochemical variables, owing to the high cost of some sensors and technological limitations (Bittig et al, 2019;Chai et al, 2020).…”

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

“…BGC-Argo is based on integrating new sensors onto standard float platforms to measure six BGC ocean variables: chlorophyll fluorescence, particle backscatter, dissolved oxygen, nitrate, pH, and irradiance, in addition to temperature and salinity. While Deep-Argo profiles require some increase in data management effort in terms of data processing and new quality control procedures, the introduction of BGC float data into the Argo data system has generated multiplicative challenges due to their complexity (Bittig et al, 2019). To minimize the impact of adding BGC data to the Argo data streams, the CTD and BGC data are stored in two separate profile data files: a Core-profile file, which contains the CTD data, and a BGC-profile file, which contains all the measured intermediate BGC parameters as well as the computed ocean state variables.…”

Preparing the New Phase of Argo: Scientific Achievements of the NAOS Project

“…Authors highlighted the specific behaviors of Mediterranean waters, largely on the basis of NAOS BGC-Argo data. More recently, Bittig et al (2019) reviewed the latest advancements in QC and deployment best practices for BGC-Argo floats. NAOS knowhow contributed to this synthesis, in particular with regard to deployment protocols and also the acquisition and processing of ancillary data required for QC.…”

“…Prior to deployment, data from RemA sensors (OCR504 and ECO triplet) were collected in dark conditions to evaluate their offset drift since factory calibration. A night profile was programmed as an in situ check of this offset down to 1000 m to cover a relatively large temperature range, which helped to determine the response of OCR to temperature (Bittig et al, 2019). Oxygen was measured by the optode with an individual factory multi-point calibration, as recommended by Bittig et al (2018a).…”

“…One major contribution of the NAOS project is its implementation of the procedure for managing oxygen data in the Argo data stream. This activity contributed to the BGC-Argo component (Biogeochemical-Argo Planning Group, 2016), and was conducted in close collaboration with European and international partners (Bittig et al, 2019). Through NAOS therefore, a manual describing oxygen data management processing was written and kept up-to-date (Thierry et al, 2018a), and in addition, the Real-Time and Delayed-Mode Quality Control procedure for oxygen data acquired by Argo floats was established (Schmechtig et al, 2016;Thierry et al, 2018b).…”