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Triple oxygen isotope measurements of sea water from CTD bottles and the ships non-toxic underway supply for cruise AMT16

Originator's Protocol for Data Acquisition and Analysis

This data originates from analyses on samples collected from CTD Niskin casts and from the non-de-aerated underway seawater supply between 20 May 2005 and 29 June 2005.

50 ml of each sample was collected in brown borosilicate glass bottles with double-rinsed clear plastic liners and red polypropylene screw caps. The bottles were shipped to the Institute of Earth Sciences at the Hebrew University of Jerusalem, Israel for analysis.

The 17O/16O and 18O/16O isotope ratios of seawater were obtained by flourination and mass spectrometry (See Barkan and Luz, 2010; 2000 and Luz et al., 1999). First, 2 µl of water was converted into O2 gas using CoF3 reagent. A Thermo-Finnigan Delta Plus isotope-ratio mass spectrometer (Thermo Scientific, Bremen, Germany) was used to measure the isotopic ratios. The reported isotopic ratios are averages of 3 runs and reported with respect to VSMOW. The mass spectrometer errors (standard error of the mean (n = 90) multiplied by Student's t factor for a 95% confidence limit) in d18O and d17O are 0.004 and 0.008 ‰, respectively.

References Cited

Luz, B. and Barkan, E., 2010. Variations of 17O/16O and 18O/16O in meteroic waters. Geochimica et Cosmochimica Acta 74, 6276-6286.

Luz, B. and Barkan, E., 2000. Assessment of oceanic productivity with the triple-isotope composition of dissolved oxygen. Science 288, 2028-2031.

Luz, B, Barkan, E. Bender, M.L., Thiemens, M.H., Boering, K.A., 1999. Triple-isotope composition of atmospheric oxygen as a tracer of biosphere productivity. Nature 400, 547-550.

Instrumentation Description

Not applicable for this data set.

BODC Data Processing Procedures

Data were submitted in pdf format in the journal article Luz and Barkan, 2010 and archived under BODC's accession number HUJ110030. Time, date, station, cast and Niskin were obtained from the crusie report, and matched to the dataset using the latitude, longitude and depth. Sample metadata (CTD cast, bottle number, depth, lat, lon) were checked against information held in the database. There were a number of discrepancies: some CTD sampling times mismatched as the data file contained times of analysis rather than collection. There were slight discrepancies between the lat and lon provided in the original data and in the cruise log. The data from the cruise log was loaded. Underway files were recored with a depth of 2 m in the original data, but loaded with 5 m according to the cruise log. The underway samples recorded in the originator file on 04 and 06 June 2005 at 11:18 and 10:43 respectively, were loaded with times of 04:46 and 05:13 respectively according to the central navigation log for the lat/lon positions supplied.

The data originator provided 17-O excess data. This data was not loaded as it is a derived parameter and can be calculated from the following formula: 17O excess = d17O - 0.528 d18O.

The isotopic enrichment data were provided in parts per thousand which is consistent with the BODC parameter code units, so no conversion was applied.

The data were reformatted and loaded in BODC's samples database under Oracle Relational Database Management System. Data were marked up with BODC parameter codes and loaded into the database. Individual samples were matched through rosette sampling bottle and depth.

A parameter mapping table is provided below;

Data Quality Report

BODC was not advised of any specific quality issues with the data. The data were checked visually and no values were flagged by BODC.

Problem Report

Not relevant to this data set.