Isotopic composition of dissolved inorganic carbon in sea water analyzed since 1990 at LOCEAN (DICisotopes)
|Contributor(s)||Racapé Virginie, Reverdin Gilles, Pierre Catherine, Lo Monaco Claire, Metzl Nicolas, Leseurre Coraline, Bourlès Bernard, Demange Jérôme, Naamar Aïcha, Lherminier Pascale, Mercier Herle, Perez Fiz, Jeandel Catherine|
LOCEAN has been in charge of analyzing the isotopic composition of the dissolved inorganic carbon (DIC) in sea water collected during a series of cruises or ships of opportunity mostly in the southern Indian Ocean , the North Atlantic, and the equatorial Atlantic, but also in the Mediterranean Sea and in the equatorial Pacific.
The LOCEAN sea-water samples for δ13CDIC were collected in 125 ml glass bottles and poisoned with HgCl2 (1 ml of saturated solution) before storage in a dark room à 4°C until their measurement. The DIC was extracted from the seawater by acidification with phosphoric acid (H3PO4 85%) and CO2 gas that was produced was collected in a vacuum system following the procedure described by Kroopnick (1974). The isotopic composition of CO2 was determined using a dual inlet-isotopic ratio mass spectrometer (SIRA9-VG) by comparing the 13C/12C ratio of the sample to the 13C/12C ratio of a reference material, the Vienna-Pee Dee Belemnite (V-PDB). The isotopic composition is expressed in the δ-unit defined by Craig (1957)(method type 2). Experience showed that samples older than 3-4 years are likely to have experienced conservation issues and have been dismissed. The mass spectrometer has worked very well until 2014-2015. Afterwards, its aging as well as the aging of the preparation line resulted in more data loss, and often less accurate results. The preparation line was renovated in 2019, and analyses in 2020 were run manually, often repeating the measurement a second time for each sample.
Up to 2007-2008, δ13CDIC values have a precision of±0.01 ‰ (Vangriesheim et al.,2009) and a reproducibility of±0.02 ‰. After an interlaboratory comparison exercise led by Claire Normandeau (Dalhousie University), results suggest that recent LOCEAN samples have a slightly poorer reproducibility (±0.04 ‰ ) as well as an offset of -0.13‰ (details available in Reverdin et al., ESSD 2018) that is confirmed by Becker et al. 2016 work by comparison with other cruises after removing the anthropogenic signal. Recent comparisons in early May 2021 with Orsay GEOPS facility samples suggest that the current offset is much smaller and might be +0.03‰.
To improve data quality, LOCEAN is in the process of installing a cavity ring down spectrometry (CRDS) by coupling a Picarro G2131-I CRDS with a CO2 extractor (Apollo SciTech) that will measure at the same time DIC (method type 3).
Part of the data set, as well as a scientific context and publications are also presented on the WEB site https://www.locean-ipsl.upmc.fr/oceans13c.
Individual files correspond to regional subsets of the whole dataset. The file names are based on two letters for the region followed by (-) the cruise or project name (see below) followed by –DICisotopes, followed by either -s (surface data) or -b (subsurface data), and a version number (-V0, …): example SI-OISO-DICisotopes-s-V0; the highest version number corresponds to the latest update of the cruise/project data set, and can be directly downloaded. Earlier versions can be obtained on request, but are not recommended. The region two letters are the followings:
- SI: station and surface data in the Southern Indian Ocean that include cruises :
INDIGO I (1985 – stn) (https://doi.org/10.17600/85000111)
ANTARES (1993 – stn & surf) (https://doi.org/10.17600/93000600)
- EA: station and surface data in the Tropical Atlantic Ocean that include cruises :
EQUALANT (1999 & 2000 – surf) (https://doi.org/10.18142/98)
EGEE (2005 to 2007 – stn & surf) (https://doi.org/10.18142/95)
PIRATA (since 2013 – stn & surf) (https://doi.org/10.18142/14)
- NA : station and surface data in the North Atlantic Subpolar gyre that include cruises :
RREX (2017 – stn & surf) (https://doi.org/10.17600/17001400)
- MS: station data in the Mediterranean sea that include cruises :
ALMOFRONT 1 (1991 – stn) (https://doi.org/10.17600/91004211)
VICOMED 3 (1990 – stn) (https://doi.org/10.17600/90000711)
- PO: tropical Pacific that include cruises :
PANDORA (2012 – stn) (https://doi.org/10.17600/12010050)
(*) The values for cruises OISO19, 21 and 22 are doubtful (for some, too low) and will require further investigation to find whether adjusted values can be proposed.
(**) Some of the OVIDE cruises are also referred to as or GEOVIDE (in 2014), and BOCATS (in 2016). The values of the OVIDE 2010 stations are doubtful (too low), but no particular error was found, and they have been left in the files.
The files are in csv format reported as:
Temperature qc, salinity qc, d13CDIC qc are quality indices equal to:
|Utilisation||Data are published without any warranty, express or implied. The user assumes all risk arising from his/her use of data. Data are intended to be research-quality and include estimates of data quality and accuracy, but it is possible that these estimates or the data themselves contain errors. It is the sole responsibility of the user to assess if the data are appropriate for his/her use, and to interpret the data, data quality, and data accuracy accordingly. Authors welcome users to ask questions and report problems (to be communicated to Gilles Reverdin).|
|Acknowledgements||CISE-LOCEAN is housed by the LOCEAN laboratory and is part of the OSU ECCE Terra analytical facilities. Support by OSU ECCE Terra, by LOCEAN, and by various French national institutes and programs is gratefully acknowledged (including INSU/CNRS, IFREMER, IRD, IPEV, LEFE program, ANR GEOVIDE, IPSL), as well as support of different French ‘Services nationaux d’Observation’, such as PIRATA, SSS and OISO/CARAUS. Many of the data originate from cruises on French Research vessels: R.V. Noroit, Suroit, Thalassa, Atalante, Marion Dufresne 2. Some data were collected during research cruises on non-French vessels, such as BOCATS in 2016 on the Spanish R/V Sarmiento de Gamboa. The SURATLANT data were collected on merchant vessels with support of EIMSKIP in Iceland.|