Dataset: Carbonate chemistry and isotopes

Samples for carbonate chemistry analysis were collected from shipboard seawater intake (10 m depth) on basin-wide transects of the North Pacific between Hong Kong and Long Beach, California onboard the M/V OOCL Tianjin and the M/V OOCL Tokyo (each individual transect has a unique Cruise ID). Sea surface temperature and salinity at the time of sample collection were determined using a Sea-Bird Electronics SBE45 thermosalinograph installed in the ship’s seawater intake. To prevent biofouling that could cause respiration in the ship’s seawater lines [Juranek et al., 2010], intake lines between the anticorrosive sea chest and the sampling port were purged with bleach and freshwater between every cruise.

Samples for both dissolved inorganic carbon (DIC) and total alkalinity (TA) analysis were collected into 250 mL bottles with greased ground glass stoppers and poisoned with 100 μL of saturated mercuric chloride solution. DIC concentrations were determined in the laboratory through a combination of manometric measurements (DIC_SIL, Quay and Stutsman, 2003) and measurements with an Apollo SciTech AS-C3 IR-based DIC analyzer (DIC_IR). Certified reference materials (Andrew Dickson, UCSD) were used for calibration and determination of sample-specific measurement error for all DIC measurements using the AS-C3 analyzer (DIC_IR_uncert), with mean uncertainty of ± 4 μmol kg^-1 for the entire dataset. Comparison of duplicate samples analyzed both manometrically and with the AS-C3 analyzer (n = 111) agree to within 1 ± 9 μmol kg^-1 and indicate uncertainty of ± 8 μmol kg^-1 in the manometric measurements (DIC_SIL). δ¹³C of the DIC samples measured manometrically was determined following the methods detailed in Quay and Stutsman (2003). TA samples were measured using an automated, open-cell potentiometric titration system (Dickson et al., [2007]; SOP 3b), with sample-specific measurement error quantified based on certified reference materials (Andrew Dickson, UCSD) measured with each sample batch (TA_uncert, mean uncertainty of ± 2 μeq kg^-1 for the entire dataset).