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Notes: WORLD OCEAN DATABASE (WOD)

The WOD18 is an NCEI product and an IODE (International Oceanographic Data and Information Exchange) project.

For any questions about this product, please e-mail OCLhelp desk.


WOD18 was released on September 20, 2018. It contains all data in the World Ocean Database up to unique cast 18,604,996, roughly all data added up to December 31, 2017. There are some plankton tows added after that date (and unique cast number). These plankton tow data are from accession numbers 0051894, 0051914, and 0046299. There are also 3,209 casts from the Argo program with latter unique casts higher than the above cast number. A list of these casts can be found here. It is important to note the exact data set of WOD18 as it is the input, both data and quality flagging for the World Ocean Atlas 2018 (WOA18) prerelease.

Some major additions for WOD18 are the inclusion of BioArgo data, the addition of more than one million glider cycles, and the change of oxygen, nutrient, and tracer units from per liter to per kilogram.

Table 1 gives a list of the changed units

Oceanographic variableOld units (before WOD18)WOD18 units
OxygenMilli-liter per liter (ml/l)Micro-mole per kilogram (µmol/kg)
PhosphateMicro-mole per liter (µmol/l)Micro-mole per kilogram (µmol/kg)
SilicateMicro-mole per liter (µmol/l)Micro-mole per kilogram (µmol/kg)
Nitrate and Nitrate+NitriteMicro-mole per liter (µmol/l)Micro-mole per kilogram (µmol/kg)
HeliumNano-mole per liter (nmol/l)Nano-mole per kilogram (nmol/kg)
ArgonNano-mole per liter (nmol/l)Nano-mole per kilogram (nmol/kg)
NeonNano-mole per liter (nmol/l)Nano-mole per kilogram (nmol/kg)
CFC-11Pico-mole per liter (pmol/l)Pico-mole per kilogram (pmol/kg)
CFC-12Pico-mole per liter (pmol/l)Pico-mole per kilogram (pmol/kg)
CFC-113Pico-mole per liter (pmol/l)Pico-mole per kilogram (pmol/kg)

Table 1 notes:
1 mole=106 µmol=109 nmol=1012 pmol
1 ml/l of O2 is approximately 43.570 µmol/kg (assumes a molar volume of O2 of 22.392 l/mole and a constant seawater potential density of 1025 kg/m3).
The conversion of units on a per-volume (e.g., per liter) to a per-mass (e.g., per kilogram) basis assumes a constant seawater potential density of 1025 kg/m3.

Please note that BioArgo was added during the last quarterly update of WOD (May, 2018). The data were in the WOD18 units, but the unit label still noted the old unit. Further, over the last two updates (Jan, 2018; May, 2018) data from the GLODAPv2 project were added to WOD. In that process some values of Nitrate+Nitrite and pH were corrupted. This problem has been rectified with the release of WOD18.

At this time, WOD18 contains prerelease data and flags for the WOA18. The final release of WOD18 data and flags will coincide with the final released fields of WOA18 (later 2018/early 2019), at which time the quality flags will reflect the full set of quality assurance which went into the calculations of WOA18.

More information about WOD18 can be found in:
Boyer, T. P., O. K. Baranova, C. Coleman, H. E. Garcia, A. Grodsky, R. A. Locarnini, A. V. Mishonov, C. R. Paver, J. R. Reagan, D. Seidov, I. V. Smolyar, K. Weathers, M. M. Zweng,(2018): World Ocean Database 2018. A. V. Mishonov, Technical Editor, NOAA Atlas NESDIS 87.