Essential Ocean Variables

To be able to deliver ocean forecasts and early warnings, climate projections and assessments and protect ocean health and its benefits, it is vital to measure Essential Ocean Variables (EOVs).

They help us interpret the connection between the ocean and elements such as the atmosphere, biosphere, hydrosphere, cryosphere, and anthroposphere.

Critical EOVs for us include those linked to ocean circulation and the distribution of and transport of heat, salt and other water properties

Because EOVs are perennial, they allow the observing system to change and develop around them as technology and capability evolve.

Focusing on EOVs enables ocean observations that cut across different observing platforms and offer the best, most cost effective plan for providing an optimal global view for each EOV.

Our GOOS Expert Panels identify the EOVs to use, based on:

  • Impact: the variable addresses climate, operational ocean services and ocean health and also contributes to understanding from a scientific perspective or application from a service perspective.
  • Feasibility: it is technically, politically and economically feasible to observe or derive the variable on a global scale using proven, scientifically understood methods.

When EOVs are identified, our Expert Panels create and share a series of recommendations. These include what measurements are made, observing options and data management guidelines.

The majority of EOVs are also Essential Climate Variables (ECVs) defined by the Global Climate Observing System. ECVs cover atmospheric, oceanic, and terrestrial domains. A number of OCG networks measure atmospheric and oceanic ECVs.

EOV specification sheets

Click to download each EOV specification sheet for details on requirements, tracing through from applications to phenomena to observing, and for authors for queries. The columns indicate the GOOS expert panel that has lead responsibility for each EOV.

Download the 2023 EOV specification sheet template here.


Biochemistry Biology and Ecosystems
Sea state
Ocean surface stress
Sea ice
Sea surface height
Sea surface temperature
Subsurface temperature
Surface currents
Subsurface currents
Sea surface salinity
Subsurface salinity
Ocean surface heat flux
Ocean bottom pressure
Turbulent diapycnal fluxes (*pilot)
Inorganic carbon
Transient tracers
Particulate matter
Nitrous oxide
Stable carbon isotopes
Dissolved organic carbon
Phytoplankton biomass and diversity
Zooplankton biomass and diversity
Fish abundance and distribution
Marine turtles, birds, mammals abundance and distribution
Hard coral cover and composition
Seagrass cover and composition
Macroalgal canopy cover and composition
Mangrove cover and composition
Microbe biomass and diversity (*pilot)
Invertebrate abundance and distribution (*pilot)
Cross-disciplinary (including human impact)
Ocean colour
Marine debris (*pilot)
Ocean sound

Where next?

Who makes up GOOS

Find out about the Global Ocean Observing System community.

Click here

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