Usage of "sea" vs "ocean" in names

Currently there is a mix of variable names using "ocean" and "sea", without a clear concept of what, if anything, is the difference between the two. Or if one word was chosen over the other for any reason other than etymology. "Sea" seems to be the more prevalent of the two.

We know not every sea is an ocean, but is every ocean a sea? If so, is standardizing on "sea" preferable, being the more general word?

For the name skin_temperature_at_surface_over_ocean, the people in my sphere would prefer to use "sea" instead of "ocean". Why was "ocean" chosen here?

Is there ever a use case for using "water", if the lake/sea/ocean distinction is unimportant? Currently there is both lake_depth and sea_water_depth. (And the description of sea_water_depth is "The depth of the ocean floor below the surface of the sea," which highlights the interchangeability of the two words.)

If we want to continue to use a mix of the two words, it would be nice to have a clearer description of why and when each should be used.

@svahl991

@svahl991 After staring at the CF conventions a little bit, I think I've come to a conclusion on how to define the usage of "sea" vs "ocean". This is not explicitly defined anywhere in the CF conventions, but seems to be true just from observing the distribution of these terms in existing names.

The CF names use a mix of “sea” and “ocean”, but it doesn't seem to be arbitrary; it seems to be split by the type of word/part of speech being used for the term:

In the context of some specific adjective phrases, "sea" is used (and this seems to be an exhaustive list):
- sea_water
- sea_ice
- sea_level
- sea_salt
- sea_surface
- sea_floor
- sea_binary_mask (this is a one-off but does fit)
- sea_area (this is the only one that's a bit iffy with the above definition, but it is used consistently)
In other contexts, mostly when a noun, "ocean" is used
- ocean_heat_y_transport
- ocean_meridional_overturning_mass_streamfunction
- ocean_sigma_coordinate
- etc., the examples are a lot more varied

There are a very small number of exceptions to this rule (to be specific exactly two: tendency_of_surface_snow_amount_due_to_drifting_into_sea and mass_flux_of_nitrogen_compounds_expressed_as_nitrogen_into_sea_from_rivers) but overall the rule seems to hold very well. And best of all, this would require only two changes to the existing ESM standard names from what I can tell: lower_bound_for_depth_of_sea_temperature_for_nsstm --> lower_bound_for_depth_of_ocean_temperature_for_nsstm, and upper_bound_for_depth_of_sea_temperature_for_nsstm --> upper_bound_for_depth_of_ocean_temperature_for_nsstm

Based on this information, I would propose adding the following stanza to StandardNamesRules.rst:

Unless otherwise specified, `water` refers to all types of water in any phase (e.g. solid, liquid, gas,
fresh water, salt water, etc.). The terms `sea` and `ocean` are synonymous, though new names
should default to using `ocean` unless part of one of the following common phrases:
   - sea_water
   - sea_ice
   - sea_level
   - sea_salt
   - sea_surface
   - sea_floor
   - sea_binary_mask
   - sea_area

If you approve of this definition, I can open a PR to add it and update the few out-of-spec names.

Yes, this all seems pretty clear and reasonable. Except for maybe sea_surface, which intersects with issue #150. It feels to me like ocean_temperature_at_surface is more consistent with other names in the convention than sea_surface_temperature. I suppose the same case could be made regarding sea_floor--that instead it should be ocean_XXX_at_floor or *_at_bottom. However, I don't know if this consistency is worth changing names that are already widely used and accepted.

I would agree with Mike's rules. I would be reluctant to use the word ocean except in the context of a coupled model. sea_surface_temperature should be preserved as a common term for an atmosphere-only boundary condition.

…

On Mon, Aug 31, 2026 at 9:42 AM Steve Vahl ***@***.***> wrote: *svahl991* left a comment (ESCOMP/ESMStandardNames#156) <#156 (comment)> Yes, this all seems pretty clear and reasonable. Except for maybe sea_surface, which intersects with issue #150 <#150>. It feels to me like ocean_temperature_at_surface is more consistent with other names in the convention than sea_surface_temperature. I suppose the same case could be made regarding sea_floor--that instead it should be ocean_XXX_at_floor or *_at_bottom. However, I don't know if this consistency is worth changing names that are already widely used and accepted. — Reply to this email directly, view it on GitHub <#156?email_source=notifications&email_token=AEIZ77EMMBH7TKDZJ6MKP5L5MWMHTA5CNFSNUABFM5UWIORPF5TWS5BNNB2WEL2JONZXKZKDN5WW2ZLOOQXTKNBYGA3TGMRZGUZ2M4TFMFZW63VKON2WE43DOJUWEZLEUVSXMZLOOSWGM33PORSXEX3DNRUWG2Y#issuecomment-5480732953>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AEIZ77GS5SGUUFZE6OHFIVD5MWMHTAVCNFSNUABFKJSXA33TNF2G64TZHMZDINJUHE3DSMRWHNEXG43VMU5TIOJWGI2DKOBYHA4KC5QC> . You are receiving this because you are subscribed to this thread.Message ID: ***@***.***>

Resolve ambiguity in terminology for "surface", "ocean vs sea", "skin…

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Usage of "sea" vs "ocean" in names #156

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mkavulich commented on Aug 28, 2026

svahl991 commented on Aug 31, 2026

dudhia commented on Aug 31, 2026

mkavulich commented on Oct 8, 2026

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