GLODAPv2.2022: the latest version of the global interior ocean biogeochemical data product

Abstract. The Global Ocean Data Analysis Project (GLODAP) is a
synthesis effort providing regular compilations of surface-to-bottom ocean
biogeochemical bottle data, with an emphasis on seawater inorganic carbon
chemistry and related variables determined through chemical analysis of
seawater samples. GLODAPv2.2022 is an update of the previous version,
GLODAPv2.2021 (Lauvset et al., 2021). The major changes are as follows: data
from 96 new cruises were added, data coverage was extended until 2021, and
for the first time we performed secondary quality control on all sulfur
hexafluoride (SF6) data. In addition, a number of changes were made to
data included in GLODAPv2.2021. These changes affect specifically the
SF6 data, which are now subjected to secondary quality control, and
carbon data measured on board the RV Knorr in the Indian Ocean in 1994–1995 which
are now adjusted using certified reference material (CRM) measurements made at the time. GLODAPv2.2022
includes measurements from almost 1.4 million water samples from the global
oceans collected on 1085 cruises. The data for the now 13 GLODAP core
variables (salinity, oxygen, nitrate, silicate, phosphate, dissolved
inorganic carbon, total alkalinity, pH, chlorofluorocarbon-11 (CFC-11), CFC-12, CFC-113, CCl4,
and SF6) 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 converted to World Ocean Circulation
Experiment (WOCE) exchange format and (ii) as a merged data product with
adjustments applied to minimize bias. For the present annual update,
adjustments for the 96 new cruises were derived by comparing those data with
the data from the 989 quality-controlled cruises in the GLODAPv2.2021 data
product using crossover analysis. SF6 data from all cruises were
evaluated by comparison with CFC-12 data measured on the same cruises. For
nutrients and ocean carbon dioxide (CO2) chemistry comparisons to
estimates based on empirical algorithms provided additional context for
adjustment decisions. The adjustments that we applied 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 µmol kg−1 in dissolved inorganic carbon, 4 µmol kg−1
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 CO2 fugacity
(fCO2), were not subjected to bias comparison or adjustments. The original data, their documentation, and DOI codes are available at the
Ocean Carbon and Acidification Data System of NOAA NCEI (https://www.ncei.noaa.gov/access/ocean-carbon-acidification-data-system/oceans/GLODAPv2_2022/, last access: 15 August 2022). 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 https://doi.org/10.25921/1f4w-0t92 (Lauvset et al.,
2022). These bias-adjusted product files also include significant ancillary
and approximated data, which were obtained by interpolation of, or
calculation from, measured data. This living data update documents the
GLODAPv2.2022 methods and provides a broad overview of the secondary quality
control procedures and results.
