C-RAID autumn delivery 2022 – activity report

This document is the C-RAID project activity report in automn 2022

C-RAID drifters NetCDF format reference manual - NetCDF conventions and Reference Tables

This document specifies the NetCDF file format used to store the drifter data and meta-data processed in the framework of the C-RAID project

C-RAID drifters Quality Control Manual

This document is the quality control manual for drifter data processed in the framework of the C-RAID project. It is derived from “Argo Quality Control Manual for CTD and Trajectory Data” (http://dx.doi.org/10.13155/33951). Specific information about the drifting buoy was also recovered from the “Guide to Drifting Data Buoys”, UNESCO, 1988 (https://www.oceandocs.org/handle/1834/2734). The document describes two levels of quality control: - Real Time Quality Control (RTQC) tests that perform a set of agreed automatic checks; - Delayed-Mode Quality Control (DMQC) tests and procedures to be performed by an operator

Why did deep convection persist over four consecutive winters (2015-2018) southeast of Cape Farewell?

After more than a decade of shallow convection, deep convection returned to the Irminger Sea in 2008 and occurred several times since then to reach exceptional convection depths (> 1500 m) in 2015 and 2016. Additionally, deep mixed layers deeper than 1600 m were also reported southeast of Cape Farewell in 2015. In this context, we used Argo data to show that deep convection occurred southeast of Cape Farewell (SECF) in 2016 and persisted during two additional years in 2017 and 2018 with a maximum convection depth deeper than 1300 m. In this article, we investigate the respective roles of air-sea buoyancy flux and preconditioning of the water column (ocean interior buoyancy content) to explain this 4-year persistence of deep convection SECF. We analyzed the respective contributions of the heat and freshwater components. Contrary to the very negative air-sea buoyancy flux that was observed during winter 2015, the buoyancy fluxes over the SECF region during the winters of 2016, 2017 and 2018 were close to the climatological average. We estimated the preconditioning of the water column as the buoyancy that needs to be removed (B) from the end-of-summer water column to homogenize it down to a given depth. B was lower for the winters of 2016-2018 than for the 2008-2015 winter mean, especially due to a vanishing stratification from 600 down to similar to 1300 m. This means that less air-sea buoyancy loss was necessary to reach a given convection depth than in the mean, and once convection reached 600 m little additional buoyancy loss was needed to homogenize the water column down to 1300 m. We show that the decrease in B was due to the combined effects of the local cooling of the intermediate water (200-800 m) and the advection of a negative S anomaly in the 1200-1400 m layer. This favorable preconditioning permitted the very deep convection observed in 2016-2018 despite the atmospheric forcing being close to the climatological average

C‐RAID ‐ Final Activity Report

This activity rapport summarizes the actions carried out for the first phase of the C-RAID project (EEA work on Specific Contract 4 n° 3436_R0‐COPERNICUS_EEA.57652)

C-RAID– Phase 2

This activity rapport summarizes the actions carried out for the second phase of the C-RAID project (EEA work on Specific Contract 4 n° 3436_R0-COPERNICUS_EEA.57652)

Computing inventories of anthropogenic CO2 in the eastern subpolar North Atlantic using OVIDE data

The highest anthropogenic CO2 (Cant) inventories of all the oceans are found in the subpolar North Atlantic (SPNA). The OVIDE section crosses the SPNA from Greenland to Portugal and is repeated biennially since 2002. Therefore, OVIDE data allow evaluating the evolution of inventories of anthropogenic CO2 (Cant) in the SPNA. This oceanic region is known to host water formation and ventilation processes that change the water mass volumetric census year by year. Changes in the volumetric census cause differences in the Cant inventory estimates (Pérez et al., 2008). Consequently, Pérez et al. (2010) proposed a method for computing Cant inventory in the SPNA taking into account the volumetric census variability and a bathymetric adjustment. This method has been recently revised. The initial methodology and the recent improvements are detailed in this report.Les inventaires de CO2 anthropique (Cant) les plus hauts de tous les océans sont trouvés en Atlantique Nord subpolaire. La section OVIDE traverse l’Atlantique Nord Subpolaire du Groenland au Portugal ; elle est visitée tous les deux ans depuis 2002. Les données acquises pendant les campagnes OVIDE sont donc un outil très intéressant pour étudier l’évolution des inventaires de Cant dans l’Atlantique Nord subpolaire. Dans cette région océanique il y a des processus de ventilation et de formation de masses d’eau qui provoquent des changements de volume de masses d’eau d’une année à l’autre, et ces derniers causent des différences sur le calcul d’inventaires de Cant (Pérez et al., 2008). Donc Pérez et al. (2010) ont proposé une méthode pour calculer des inventaires de Cant en corrigeant la variabilité du volume des masses d’eau et en tenant compte de la bathymétrie du bassin. Cette méthode a était récemment révisée, et les améliorations de la méthode initiale sont détaillées et quantifiées dans ce rapport

LOCODOX: a Software for Argo Oxygen data correction

<p>A few modifications from C. Kermabon and T. Reynaud</p>If you use this software, please cite it as below

LOCODOX: a Software for Argo Oxygen data correction - User Manual

LOCODOX is a MATLAB based interactive software that corrects dissolved oxygen concentration data acquired by Argo profiling floats. The correction schemes are based on Takeshita et al (2013) and Bittig and Kortzinger (2018). Three types of correction are proposed : a pressure dependent correction, a time drift correction and a slope/ offset correction (also called Gain correction). LOCODOX works with Argo v3.1 netcdf files and provides files with corrected and well formatted delayed mode Argo data compliant with the Argo format (Argo Data Management Team, 2019).  LOCODOX corrects only oxygen data available in the vertical profiles. This document describes the methodology and the strategy followed by the tool, and it explains how to install and use LOCODOX.LOCODOX est un logiciel interactif développé sur la base du progiciel MATLAB pour corriger les valeurs de concentration d’oxygène dissous dans l’eau de mer acquises par les profileurs dérivants ARGO. Les schémas de correction sont basés sur les travaux de Takeshita et al (2013) and Bittig et Kortzinger (2018). Ces schémas proposent des corrections de la dépendance à la pression, de la dérive temporelle et du gain. LOCODOX lit les fichiers netcdf au format ARGO v3.1 et produit en sortie des fichiers temps différé compatible au format ARGO (Argo Data Management Team, 2019). LOCODOX ne corrige que les données des profils verticaux. Ce document décrit la méthodologie et la stratégie suivies dans ce logiciel, il explique aussi la procédure d’installation et d’utilisation de LOCODOX