WOA23¶

World Ocean Atlas 2023

Available

At a glance¶

Note on period: This is the period of the input observations. Temperature and salinity climatologies (by decade and by climate normal) use 1955–2022; dissolved oxygen and nutrient climatologies use all data for 1965–2022. The product is a static set of fixed-period mean states, not a continuous time series; the NCEI metadata gives the temporal extent as 1955-01-01 to 2022-12-31.

Overview¶

The World Ocean Atlas 2023 (WOA23) is a set of objectively analyzed, quality-controlled climatological fields of temperature, salinity, oxygen, phosphate, silicate and nitrate, built by NOAA NCEI from profile data in the World Ocean Database 2023 (WOD23). Temperature and salinity are provided on 0.25° and 1° grids for seven decades in 1955–2022 and for the 1971–2000, 1981–2010 and 1991–2020 climate normals; oxygen, AOU, percent oxygen saturation and nutrients are on a 1° grid. It is the most widely used reference for ocean model initial and boundary conditions, anomaly baselines, and the verification of models and satellite products.

What changes with the successor¶

WOA18 → WOA23¶

Transition: 2024-02

The successor to WOA18, built from the observations added to the World Ocean Database since then and updated quality control. Temperature and salinity now extend to 2022 instead of 2017, 1971–2000 and 1991–2020 climate normals were added, and new objectively analyzed standard deviation and standard error of the analysis fields are included. Density, conductivity and mixed layer depth, which were on the WOA18 data page, are not in the WOA23 variable list.

Sources: NCEI World Ocean Atlas product page · WOA23 Product Documentation (Reagan et al. 2023) · WOA18 Product Documentation · WOA18 data access page

Available variables¶

Based on the WOA23 data access page and the Product Documentation. File names follow woa23_[period][variable code][time code][grid].nc (e.g. woa23_decav91C0_t00_01.nc), and in-file variables follow [variable code]_[field code] (e.g. t_an). Variable codes: temperature t, salinity s, dissolved oxygen o, nitrate n, phosphate p, silicate i. Percent oxygen saturation uses code O and AOU uses code A (e.g. O_an, A_an).

instantaneous mean accumulated maximum minimum static — instantaneous: value at the time stamp · mean/accumulated/maximum/minimum: over the indicated interval · static: does not change with time

Objectively analyzed climatologies (main fields, *_an)¶

Statistical fields (temperature shown; other variables follow the same pattern)¶

Masks (WOA23/MASKS)¶

The full variable list is in the official documentation.

How to get the data¶

• NCEI WOA23 data access page — Web (choose variable, period, grid and format) No login needed
  • Offers CF-compliant netCDF, CSV, native ASCII and ArcGIS shapefiles. The Product Documentation discourages the legacy ASCII format because it does not explicitly give depth.
• NCEI HTTPS directory — HTTPS (wget / curl) No login needed
  • Layout is DATA/[variable]/netcdf/[period]/[grid]/, e.g. DATA/temperature/netcdf/decav91C0/1.00/woa23_decav91C0_t00_01.nc
• NCEI THREDDS (thredds-ocean) — THREDDS catalogue (HTTPServer download) No login needed
  • As of 2026-10-12, the file pages list only HTTPServer; no OPeNDAP service was shown.
• NCEI Archive (Accession 0270533) — HTTPS / FTP (complete package) No login needed
• WOA23 Figures — Web map viewer

Example code¶

Downloads the 1° annual temperature file for the 1991–2020 normal (about 80 MB) and looks at the surface values.

# pip install xarray netCDF4 requests
import requests
import xarray as xr

url = ("https://www.ncei.noaa.gov/data/oceans/woa/WOA23/DATA/temperature/netcdf/"
       "decav91C0/1.00/woa23_decav91C0_t00_01.nc")
with open("woa23_decav91C0_t00_01.nc", "wb") as f:
    f.write(requests.get(url, timeout=600).content)

# time is in 'months since 1955-01-01', which may not decode automatically, so turn decoding off
ds = xr.open_dataset("woa23_decav91C0_t00_01.nc", decode_times=False)
sst_clim = ds["t_an"].isel(time=0).sel(depth=0)
print(sst_clim.sel(lat=slice(30, 45), lon=slice(120, 135)).mean().values)

Practical tips¶

• Always check the period code in the file name. decav (average of the seven 1955–2022 decades), decav71A0/decav81B0/decav91C0 (30-year normals), 5564 to B5C2 (individual decades) and all (1965–2022 for oxygen and nutrients) are different products. For anomaly baselines, a climate normal such as decav91C0 is the usual choice.
• t_an is filled where there are no observations, using nearby data and the first-guess field. In data-sparse regions, at depth and in the early decades, read it together with t_dd (number of observations). The new objectively analyzed standard deviation and standard error of the analysis fields are also useful here.
• Monthly fields stop at 1500 m (800 m for nutrients); use seasonal or annual fields below that. Quarter-degree monthly fields exist only for the decades from 2005 and the three normals.
• The temperature data include the Cheng et al. (2014) XBT corrections and MBT corrections following Levitus et al. (2009) (Volume 1). Keep this in mind when comparing with products that use other bias corrections, such as EN4.
• The density, conductivity and mixed layer depth climatologies available in WOA18 are not on the WOA23 data page. If you need them, compute them from WOA23 temperature and salinity, or use WOA18 and cite it as the source.

Notices and change history¶

References for your paper¶

Dataset citation¶

WOA23 dataset DOI (NCEI Accession 0270533) — DOI 10.25921/va26-hv25

@misc{woa23_dataset,
  author    = {Reagan, James R. and Boyer, Tim P. and Garc{\'i}a, Hern{\'a}n E. and Locarnini, Ricardo A. and Baranova, Olga K. and Bouchard, Courtney and Cross, Scott L. and Mishonov, Alexey V. and Paver, Christopher R. and Seidov, Dan and Wang, Zhankun and Dukhovskoy, Dmitry},
  title     = {World Ocean Atlas 2023},
  year      = {2023},
  publisher = {NOAA National Centers for Environmental Information},
  doi       = {10.25921/va26-hv25},
  note      = {NCEI Accession 0270533. Accessed DD MMM YYYY}
}

Reference papers¶

WOA23 Product Documentation — DOI 10.25923/a78k-gq49

@techreport{reagan2023woa23doc,
  author      = {Reagan, J. R. and Garcia, H. E. and Boyer, T. P. and Baranova, O. K. and Bouchard, C. and Cross, S. L. and Dukhovskoy, D. and Grodsky, A. and Locarnini, R. A. and Mishonov, A. V. and Paver, C. R. and Seidov, D. and Wang, Z.},
  title       = {World Ocean Atlas 2023: Product Documentation},
  institution = {NOAA National Centers for Environmental Information},
  year        = {2023},
  doi         = {10.25923/a78k-gq49}
}

Volume 1 — Temperature (NOAA Atlas NESDIS 89) — DOI 10.25923/54bh-1613

@techreport{locarnini2024woa23t,
  author      = {Locarnini, Ricardo A. and Mishonov, Alexey V. and Baranova, Olga K. and Reagan, James R. and Boyer, Timothy P. and Seidov, Dan and Wang, Zhankun and Garcia, Hernan E. and Bouchard, Courtney and Cross, Scott L. and Paver, Christopher R. and Dukhovskoy, Dmitry},
  title       = {World Ocean Atlas 2023, Volume 1: Temperature},
  institution = {NOAA National Centers for Environmental Information},
  type        = {NOAA Atlas NESDIS},
  number      = {89},
  year        = {2024},
  doi         = {10.25923/54bh-1613}
}

Volume 2 — Salinity (NOAA Atlas NESDIS 90) — DOI 10.25923/70qt-9574

@techreport{reagan2024woa23s,
  author      = {Reagan, James R. and Seidov, Dan and Wang, Zhankun and Dukhovskoy, Dmitry and Boyer, Timothy P. and Locarnini, Ricardo A. and Baranova, Olga K. and Mishonov, Alexey V. and Garcia, Hernan E. and Bouchard, Courtney and Cross, Scott L. and Paver, Christopher R.},
  title       = {World Ocean Atlas 2023, Volume 2: Salinity},
  institution = {NOAA National Centers for Environmental Information},
  type        = {NOAA Atlas NESDIS},
  number      = {90},
  year        = {2024},
  doi         = {10.25923/70qt-9574}
}

Volume 3 — Dissolved oxygen, AOU and oxygen saturation (NOAA Atlas NESDIS 91) — DOI 10.25923/rb67-ns53

@techreport{garcia2024woa23o,
  author      = {Garcia, Hernan E. and Wang, Zhankun and Bouchard, Courtney and Cross, Scott L. and Paver, Christopher R. and Reagan, James R. and Boyer, Timothy P. and Locarnini, Ricardo A. and Mishonov, Alexey V. and Baranova, Olga K. and Seidov, Dan and Dukhovskoy, Dmitry},
  title       = {World Ocean Atlas 2023, Volume 3: Dissolved Oxygen, Apparent Oxygen Utilization, and Dissolved Oxygen Saturation},
  institution = {NOAA National Centers for Environmental Information},
  type        = {NOAA Atlas NESDIS},
  number      = {91},
  year        = {2024},
  doi         = {10.25923/rb67-ns53}
}

Volume 4 — Nutrients (NOAA Atlas NESDIS 92) — DOI 10.25923/39qw-7j08

@techreport{garcia2024woa23n,
  author      = {Garcia, Hernan E. and Bouchard, Courtney and Cross, Scott L. and Paver, Christopher R. and Reagan, James R. and Boyer, Timothy P. and Locarnini, Ricardo A. and Mishonov, Alexey V. and Baranova, Olga K. and Seidov, Dan and Wang, Zhankun and Dukhovskoy, Dmitry},
  title       = {World Ocean Atlas 2023, Volume 4: Dissolved Inorganic Nutrients (phosphate, nitrate and nitrate+nitrite, silicate)},
  institution = {NOAA National Centers for Environmental Information},
  type        = {NOAA Atlas NESDIS},
  number      = {92},
  year        = {2024},
  doi         = {10.25923/39qw-7j08}
}

Acknowledgements¶

Cite the dataset DOI together with the Atlas volume for each variable you actually use (temperature Volume 1, salinity Volume 2, oxygen Volume 3, nutrients Volume 4). When you describe file formats or period codes, it also helps to cite the Product Documentation.

Information on the datasets used in this study was compiled with the help of the Korean Climate Data Navigator (KCDN) (Sim, 2026; https://doi.org/10.5281/zenodo.23300923).

Links¶

• NCEI World Ocean Atlas product page (all editions and documentation DOIs)
• WOA23 data access page
• WOA23 Product Documentation (PDF)
• WOA23 Volume 1 — Temperature
• NCEI archive metadata (Accession 0270533, version history)
• WOA18 data access page (previous edition)