Comment on essd-2026-496

Résumé fourni par la source

Abstract. The Global Ocean Data Analysis Project (GLODAP) is a synthesis effort providing surface-to-bottom ocean biogeochemical observations determined through chemical analysis of discrete bottle samples, with an emphasis on seawater inorganic carbon chemistry and related variables. Version 3 of GLODAP comprises data from 1181 cruises, spanning more than 50 years of observations (1972–2023). It includes all data from the previous GLODAPv2.2023 (Lauvset et al., 2024) together with newly added data from 57 cruises. For all cruises, 13 core variables (temperature, salinity, oxygen, nitrate, silicate, phosphate, dissolved inorganic carbon, total alkalinity, CFC-11, CFC-12, CFC-113, CCl₄, and SF6) have undergone extensive quality control with particular focus on the identification and removal of systematic differences between cruises. The data are available in two formats: (i) as submitted by the data originators, converted to World Ocean Circulation Experiment (WOCE) exchange format, and (ii) as a merged data product in which adjustments have been applied. These adjustments were determined using crossover analyses in combination with a newly developed global inversion method, the furthest-first routine. The applied adjustments are intended to remove systematic differences arising from differences in measurement methods, calibration, and/or data-handling practices, while preserving known or likely temporal trends and natural variability. The consistency of the adjusted data product is estimated to be 0.0013 for salinity, 0.7 % for oxygen, 0.4 % for nitrate, 0.5 % for silicate, 0.5 % for phosphate, 1.2 µmol kg⁻¹ for dissolved inorganic carbon, and 1.4 µmol kg⁻¹ for total alkalinity. Consistency estimates could not be derived for transient tracers, but they are believed to be consistent to better than 5 % (10 % for SF₆). The enhanced consistency enables different datasets to be used together with greater confidence. Newly introduced cruise-specific uncertainty estimates for all core variables provide more granular quantifications of remaining cruise-to-cruise inconsistencies. Additional variables, including pH, discrete CO₂ fugacity (fCO₂), isotopic tracers, and others, were not subjected to secondary quality control but are included in the data product. The original data, their documentation (metadata), and DOIs are available through the Ocean Carbon and Acidification Data System (OCADS) of NOAA’s National Centers for Environmental Information (NCEI), which also hosts the merged data product. All secondary quality control decisions and supporting information can be found in the online adjustment table (https://glodapv3.geomar.de, last accesses 26.06.2026). The product is distributed as a single global file and as four regional subsets (Arctic, Atlantic, Indian, and Pacific Oceans) under https://doi.org/10.25921/m6tp-mj50 (Lange et al., 2026). These adjusted files also include ancillary and approximated data obtained through interpolation or calculation from measured data.

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