An updated version of the global interior ocean biogeochemical data product, GLODAPv2.2020

• Main Authors: A. Olsen, N. Lange, R. M. Key, T. Tanhua, H. C. Bittig, A. Kozyr, M. Álvarez, K. Azetsu-Scott, S. Becker, P. J. Brown, B. R. Carter, L. Cotrim da Cunha, R. A. Feely, S. van Heuven, M. Hoppema, M. Ishii, E. Jeansson, S. Jutterström, C. S. Landa, S. K. Lauvset, P. Michaelis, A. Murata, F. F. Pérez, B. Pfeil, C. Schirnick, R. Steinfeldt, T. Suzuki, B. Tilbrook, A. Velo, R. Wanninkhof, R. J. Woosley
• Format: Article
• Language: English
• Published: Copernicus Publications 2020-12-01
• Series: Earth System Science Data
• Online Access: https://essd.copernicus.org/articles/12/3653/2020/essd-12-3653-2020.pdf
• ISSN: 1866-3508; 1866-3516

<p>The Global Ocean Data Analysis Project (GLODAP) is a synthesis effort providing regular compilations of surface-to-bottom ocean biogeochemical data, with an emphasis on seawater inorganic carbon chemistry and related variables determined through chemical analysis of seawater samples. GLODAPv2.2020 is an update of the previous version, GLODAPv2.2019. The major changes are data from 106 new cruises added, extension of time coverage to 2019, and the inclusion of available (also for historical cruises) discrete fugacity of <span class="inline-formula">CO₂</span> (<span class="inline-formula"><i>f</i>CO₂</span>) values in the merged product files. GLODAPv2.2020 now includes measurements from more than 1.2 million water samples from the global oceans collected on 946 cruises. The data for the 12 GLODAP core variables (salinity, oxygen, nitrate, silicate, phosphate, dissolved inorganic carbon, total alkalinity, pH, CFC-11, CFC-12, CFC-113, and <span class="inline-formula">CCl₄</span>) have undergone extensive quality control with a focus on systematic evaluation of bias. The data are available in two formats: (i) as submitted by the data originator but updated to WOCE exchange format and (ii) as a merged data product with adjustments applied to minimize bias. These adjustments were derived by comparing the data from the 106 new cruises with the data from the 840 quality-controlled cruises of the GLODAPv2.2019 data product using crossover analysis. Comparisons to empirical algorithm estimates provided additional context for adjustment decisions; this is new to this version. The adjustments are intended to remove potential biases from errors related to measurement, calibration, and data-handling practices without removing known or likely time trends or variations in the variables evaluated. The compiled and adjusted data product is believed to be consistent to better than 0.005 in salinity, 1 % in oxygen, 2 % in nitrate, 2 % in silicate, 2 % in phosphate, 4 <span class="inline-formula">µmol kg⁻¹</span> in dissolved inorganic carbon, 4 <span class="inline-formula">µmol kg⁻¹</span> in total alkalinity, 0.01–0.02 in pH (depending on region), and 5 % in the halogenated transient tracers. The other variables included in the compilation, such as isotopic tracers and discrete <span class="inline-formula"><i>f</i>CO₂</span>, were not subjected to bias comparison or adjustments.</p> <p>The original data and their documentation and DOI codes are available at the Ocean Carbon Data System of NOAA NCEI (<span class="uri">https://www.nodc.noaa.gov/ocads/oceans/GLODAPv2_2020/</span>, last access: 20 June 2020). This site also provides access to the merged data product, which is provided as a single global file and as four regional ones – the Arctic, Atlantic, Indian, and Pacific oceans – under <a href="https://doi.org/10.25921/2c8h-sa89">https://doi.org/10.25921/2c8h-sa89</a> (Olsen et al., 2020). These bias-adjusted product files also include significant ancillary and approximated data. These were obtained by interpolation of, or calculation from, measured data. This living data update documents the GLODAPv2.2020 methods and provides a broad overview of the secondary quality control procedures and results.</p>