| Summary: | The database provides discrete measurements of carbon system parameters in water samples collected at 3 stations that form the marine time series GIFT during 33 oceanographic campaigns conducted over 2005–2021. Geographic coordinates of sampling stations are provided. Some physical data (i.e. pressure, temperature and salinity) are also included. Moreover, pH data obtained with a SAMI-pH sensor (Sunburst Sensors, LLC)) attached to a mooring line deployed in the Strait of Gibraltar for the years 2016 and 2017 are provided. During the cruises, a temperature and salinity profile was obtained with a Seabird 911Plus CTD probe. 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 pH in total scale at 25 °C (pHT25), total alkalinity (AT), and inorganic nutrients (phosphate, PO43and Silicate, SiO44−). pHT25 data were obtained by the spectrophotometric method with m-cresol purple as the indicator (Clayton & Byrne 1993). Samples were taken directly from the oceanographic bottles in 10 cm path-length optical glass cells and measurements were carried out with a Shimadzu UV-2401PC spectrophotometer containing a 25 °C-thermostated cells holder. Samples for AT analysis were collected in 500-ml borosilicate bottles, and poisoned with 100 μl of HgCl2-saturated aqueous solution and stored until measurement in the laboratory. AT was measured by potential titration according to Mintrop et al. (2000) with a Titroprocessor (model Metrohm 794 from 2005-2020 and model Metrothm 888 for 2021). Water samples (5 mL, two replicates) for inorganic nutrients determination were taken, filtered immediately (Whatman GF/F, 0.7 μm) and stored frozen for later analyses in the shore-based laboratory. Nutrients concentrations were measured with a continuous flow auto-analyzer using standard colorimetric techniques (Hansen & Koroleff 1999). 2. Methods for processing the data: 3. Instrument- or software-specific information needed to interpret/reproduce the data, please indicate their location: 4. Standards and calibration information, if appropriate: 5. Environmental/experimental conditions: 6. Describe any quality-assurance procedures performed on the data: 7. People involved with sample collection, processing, analysis and/or submission, please specify using CREDIT roles https://casrai.org/credit/: Chief Scientists -I.Emma Huertas/Susana Flecha; Hydro: Who -Susana Flecha/David Roque/Silvia Amaya-Vías/Angélica Enrique; Nuts: Who -Manuel Arjonilla/ Status - final; Silicate and Phosphate Autoanalizer Hansen and Koroleff (1999) 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).” Funding was also provided by the European projects CARBOOCEAN (FP6-511176), CARBOCHANGE (FP7-264879), PERSEUS (FP7-287600) and the Junta de Andalucía TECADE project (PY20_00293). The dataset is subject to a Creative Commons License Attribution-ShareAlike 4.0 International. F.F.P. was supported by the BOCATS2 (PID2019-104279GB-C21) project funded by MCIN/AEI/10.13039/501100011033. SAV was supported by a pre-doctoral grant FPU19/04338 from the Spanish Ministry of Science, Innovation and Universities. Peer reviewed
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