Water isotopes of sea water analyzed since 1998 at LOCEAN
|Temporal extent||1998 -2020|
|Contributor(s)||Reverdin Gilles, Pierre Catherine, Akhoudas Camille, Aloisi Giovanni, Benetti Marion, Bourlès Bernard, Demange Jérôme, Diverrès Denis, Gascard Jean-Claude, Le Goff Hervé, Lherminier Pascale, Lo Monaco Claire, Mercier Herle, Metzl Nicolas, Morisset Simon, Naamar Aïcha, Sallée Jean-Baptiste, Thierry Virginie, Holliday Penny, Kanzow Torsten, Yashayaev Igor, Olafsdottir Solveig, Houssais Marie-Noëlle, Waelbroeck Claire, Massé Guillaume|
LOCEAN has been in charge of collecting sea water for the analysis of water isotopes on a series of cruises or ships of opportunity mostly in the equatorial Atlantic, in the North Atlantic, in the southern Indian Ocean, in the southern Seas, Nordic Seas, and in the Arctic. The LOCEAN data set of the oxygen and hydrogen isotope (δ18O and δD)
of marine water covers the period 1998 to 2019, but the effort is ongoing. Most data prior to 2010 (only δ18O) were analyzed using isotope ratio mass spectrometry (Isoprime IRMS) coupled with a Multiprep system (dual inlet method), whereas most data since 2010 (and a few earlier data) were obtained by cavity ring down spectrometry (CRDS) on a Picarro CRDS L2130-I, or less commonly on a Picarro CRDS L2120-I. Occasionally, some data were also run by Marion Benetti on an Isoprime IRMS coupled to a GasBench (dual inlet method) at the university of Iceland (Reykjavik). On the LOCEAN Picarro CRDS, most samples were initially analyzed after distillation, but since 2016, they have often been analyzed using a wire mesh to limit the spreading of sea salt in the vaporizer. Some of the samples on the CRDS were analyzed more than once on different days, when repeatability for the same sample was not sufficient or the daily run presented a too large drift.
Accuracy is best when samples are distilled, and for δD are better on the Picarro CRDS L2130-I than on the Picarro CRDS L2120-I. Usually, we found that the reproducibility of the δ18O measurements is within ± 0.05 ‰ and of the δD measurements within ± 0.30 ‰, which should be considered an upper estimate of the error on the measurement on a Picarro CRDS.
The water samples were kept in darkened glass bottles (20 to 50 ml) with special caps, and were often (but not always) taped afterwards. Once brought back in Paris, the samples were often stored in a cold room (with temperature close to 4°C), in particular if they were not analyzed within the next three months. There is however the possibility that some samples have breathed during storage. We found it happening on a number of samples, more commonly when they were stored for more than 5 years before being analyzed. We also used during one cruise bottles with not well-sealed caps (M/V Nuka Arctica in April 2019), which were analyzed within 3 months, but for which close to one third of the samples had breathed. We have retained those analyses, but added a flag ‘3’ meaning probably bad, at least on d-excess (outside of regions where sea ice forms or melts, for the analyses done on the Picarro CRDS, excessive evaporation is usually found with a d-excess criterium (which tends to be too low); for the IRMS analyses, it is mostly based when excessive scatter is found in the S- δ18O scatter plots or between successive data, in which case some outliers were flagged at ‘3’). In some cases when breathing happened, we found that d-excess can be used to produce a corrected estimate of δ18O and δD (Benetti et al., 2016). When this method was used a flag ‘1’ is added, indicating ‘probably good’ data, and should be thought as not as accurate as the data with no ‘correction’, which are flagged ‘2’ or ‘0’.
We have adjusted data to be on an absolute scale based on the study of Benetti et al. (2017), and on further tests with the different wire meshes used more recently. We have also checked the consistency of the runs in time, as there could have been changes in the internal standards used. On the Isoprime IRMS, it was mostly done using different batches of ‘Eau de Paris’ (EDP), whereas on the Picarro CRDS, we used three internal standards kept in metal tanks with a slight overpressure of dry air). The internal standards have been calibrated using VSMOW and GISP, and were also sent to other laboratories to evaluate whether they had drifted since the date of creation (as individual sub-standards have typically stored for more than 5-years). These comparisons are still not fully statisfactory to evaluate possible drifts in the sub-standards.
Individual files correspond to regional subsets of the whole dataset. The file names are based on two letters for the region (see below) followed by –Wisotopes and a version number (-V0, …): example SO-Wisotopes-V0; the highest version number corresponds to the latest update of the regional data set. The region two letters are the followings:
The files are in csv format reported, and starting with version V1, it is reported as:
it, is, io2, iO, iD, id are quality indices equal to:
The method type is 1 for IRMS measurements, 2 for CRDS measurement of a saline water sample, 3 for CRDS measurement of a distilled water sample.
|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)|
|Acknowledgments||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), 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. Suroit, Thalassa, Atalante, Marion Dufresne 2. Some data were collected during research cruises on non-French vessels, such as MIDAS in 2013 and BOCATS in 2016 on the Spanish R/V Sarmiento de Gamboa, HUD2014007 on Canadian R.V. Hudson, 2014 JR302 in 2014 and 2017 JR16004 cruises on U.K. HMS James Clarke Ross, the Arctic cruises in 2006-2008 and 2013 on French S.V. Tara, the Nordic seas MIZEX cruises in 2002-2004 on Swedish R.V. Oden, and the 2018 east Greenland cruise MSM76 on German R.V Maria S. Merian. The SURATLANT data were collected on merchant vessels with support of EIMSKIP in Iceland and the Nuka Arctica data set was collected on the merchant vessel Nuka Arctica from company RAL in Greenland. The WAPITI project received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program (grant agreement 637770).|