Dissolved organic carbon in the water column of the Strait of Gibraltar over 2008-2015: database generated at the GIFT (Gibraltar Fixed Time Series)

During the cruises, a temperature and salinity profile was obtained with a Seabird 911 Plus CTD probe. The accuracy of CTD measurements for temperature and salinity were 0.004 ºC and 0.005, respectively. Seawater was subsequently collected for biogeochemical analysis using Niskin bottles immersed in an oceanographic rosette platform at variable depths (from 5 to 8 levels) depending on the instant position of the interface between the Atlantic and Mediterranean flows that was identified by CTD profiles. The biogeochemical variables shown in the database are Dissolved Organic Carbon (DOC), Dissolved Oxygen (DO) and inorganic nutrients (nitrate, NO3−; Silicate, SiO44−; phosphate, PO43-). DO concentration was obtained through automated potentiometric modification of the original Winkler method using the Titroprocessor. Upon collection, flasks were sealed, stored in darkness and measured within 24 h, with an accuracy of 0.5 micromol/kg. Seawater samples for DOC determination were collected in 0.25 L acid–cleaned glass bottles and immediately filtered through precombusted (450 °C, 4 h) Whatman GF/F filters with an acid–cleaned all–glass filtration system previously rinsed with about 50 mL of the sample. Aliquots of 20 mL were collected for DOC analysis in precombusted (450 °C, 12 h) 24 mL glass vials. After acidification with H3PO4 (85%) to pH <2, they were sealed with Teflon-lined caps and stored in the dark at 4 °C until analysed in the shore-based laboratory with a commercial Shimadzu TOC-VCPH organic carbon analyser according to Alvarez-Salgado & Miller (1998). Water samples (5 mL, two replicates) for inorganic nutrients determination were collected, filtered immediately (Whatman GF/F, 0.7 μm) and stored frozen for later analyses in the shore-based laboratory with a continuous flow auto-analyzer using standard colorimetric techniques (Hansen & Koroleff 1999). Chlorophyll analysis was conducted by filtering 0.5 L samples through Whatman GF/F filters, extracting in 90% acetone, and measuring concentration by standard fluorometric methods (Parsons et al., 1984) using a Turner Designs Model 10 fluorometer.

[General Notes] The data are provided under an Attribution-ShareAlike 4.0 International license. However, if you use the data, so as to support the authors, please consider citing the above mentioned article where data collection and analytical techniques are given in detail. Here we only give a brief details and a guide to the contents of the data files. Data files are in UTF8 encoding, plain text format with comma used as the delimiter. All data files have column titles as the first line. One column is written for each measured parameter. Missing data are filled with -9. All variables but temperature have a quality flag associated with them. The values each digit can assume and their meanings follows:

This research was supported by the COMFORT project that has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 820989 (project COMFORT, "Our common future ocean in the Earth system – quantifying coupled cycles of carbon, oxygen, and nutrients for determining and achieving safe operating spaces with respect to tipping points).” Other European grants providing financial support were CARBOOCEAN (FP6-511176), CARBOCHANGE(FP7-264879), SESAME (FP6-036949) and PERSEUS (FP7-287600).

[Biogeochemical variables] GIFT_dissolved_organic_carbon_2008-2015.csv provides data from cruises conducted between 2008 and 2015. Temperature and salinity were measured in situ with a Seabird 911 Plus CTD probe. Concentrations of oxygen, dissolved organic carbon, chlorophyll and dissolved nutrients were measured in the laboratory.

This data set includes data collected between 2008 and 2015 that have been used to estimate the exchange of dissolved organic carbon between the Atlantic Ocean and the Mediterranean Sea through the Strait of Gibraltar (Long:-5.345, Lat: 36.137, Datum:WSG84) and to assess the seasonality of the fluxes.

The database provides measurements of carbon system parameters in water samples collected at 3 stations that form the marine time series GIFT during 12 oceanographic campaigns conducted over 2008-2015. Some physical data (i.e. pressure, temperature and salinity) are also included.

The data is provided as [space] delimitated plain text file within a compressed folder that also includes a single README file (in PDF format) containing a detailed description of the data structure.

Quality Indicators: Flag Meaning, 1 not quality controled, 2 good data, 3 suspect (i.e. questionable) data, 4 bad data, 5 missing data, 9 variable not measured during this cast.

The dataset is subject to a Creative Commons License Attribution-ShareAlike 4.0 International.

Peer reviewed