Methodology:
The methods used in all were based on simulated in situ incubations and productivity measured by uptake of radiocarbon. Methodology for all is largely the same, with some slight variations in the irradiance levels for incubation. Incubations lasted for 24 h and 7 depths per station were measured. A total of 449 stations are compiled that were sampled from 1983 to 2006. Details of the methodology are described in Smith et al. (2000). Any inconsistencies found within the 449 stations should be reported to the PI for correction. Additional details on data compilation are in the attached README file (PDF).

Sampling and Analytical Procedures:
Samples were obtained from CTD casts with attached Niskins on the rosette. Irradiance was determined largely using an in situ PAR sensor, but earlier cruises also used a Secchi disk. Samples had ca. 100 µCi ¹⁴C-bicarbonate added and placed in on-deck incubators flushed with flowing seawater. Most incubations lasted 24 h after which samples were filtered onto 25 mm GFF filters, rinsed with 5 mL 0.01N HCL in filtered seawater, placed in scintillation vials, and had ca. 7 mL scintillation cocktail added. Total activity added to each bottle was assessed by counting an unfiltered sample (100 µL) directly in LS cocktail. All samples were counted using a liquid scintillation counter after 24 h in darkness, and DPMs converted to absolute carbon units using known equations (Smith et al., 1977).

Chlorophyll was determined fluorometrically using standard JGOFS procedures. Samples were collected from known depths into amber polycarbonate bottles, known volumes filtered through 25 mm GFF filters under low vacuum, extracted for 24 h in 90% acetone in dark, cold conditions, and the fluorescence read before and after acidification.

Mixed layers were determined from the vertical profiles of density (sigma-t) determined from CTD profiles. A change of 0.01 kg m⁻³ from a stable surface layer reading was defined as the base of the mixed layer (Smith et al., 2013).

Integrated primary productivity and chlorophyll concentrations were determined using trapezoidal integrations through the 0.1 and 1.0% isolumes, respectively. Photosynthetically active radiation (PAR) were collected using a BioSpherical Sensor Model QSP-240 placed as close to the incubators as possible. All data were integrated from 1-minute values over the period of incubation. The integrated data by station are provided in the attached Supplemental File "Integrated Water Column Station Data" (.csv file).

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