Standard names: *Euphotic depth*

[RosmerySosaG]

Hello,

I am Rosmery SOSA from Mercator Ocean international working for Copernicus Marine service.
Date 20/05/2025

We plan to add new variables linked to MICRORYS product in the Copernicus Marine service and we would be happy to have your feedback on our proposal.

We therefore propose a variable that represents this depth and is dependent on time and position. Euphotic depth is important in marine biology models. In the MICRORYS product, it is used to determine the 3 pelagic layers we consider in the zooplankton and micronekton model configuration.

standard_name : euphotic_zone_depth

definition: The euphotic zone is the zone that extends to the depth at which the light intensity corresponds to 1% of that at the surface.

units: m

I can provide more information from my expert colleagues if needed,
Kind regards,
Rosmery SOSA

[github-actions]

Thank you for your proposal. These terms will be added to the cfeditor (http://cfeditor.ceda.ac.uk/proposals/1) shortly. Your proposal will then be reviewed and commented on by the community and Standard Names moderator.

[JonathanGregory]

Dear @RosmerySosaG

Thanks for your proposal.

Looking online, I see that the euphotic zone (also called "photic" or "sunlit") is sometimes defined as the zone where photosynthesis occurs, sometimes as the zone where photosynthesis exceeds respiration. Perhaps the latter is correct, and the former is a simplification?

That's a qualitative concept, which we should first state in the definition, I feel. Is your quantitative criterion in terms of light intensity universally employed, when precision is required about this?

As regards the standard name, we should use the word thickness, not depth, to be consistent with other standard names. Alternatively, it could be called depth_at_base_of_euphotic_zone. "Depth" is a coordinate, and "thickness" is a the vertical extent of a layer i.e. a difference between two depths.

Best wishes

Jonathan

[efisher008]

Dear Rosmery @RosmerySosaG,

Thank you for your proposal for a new standard name. The name has been added to the CF editor. I did have a longer comment to make, but I unfortunately lost this before posting, so will take some time to rewrite what I had down. The entry can be viewed here:

euphotic_zone_depth - https://cfeditor.ceda.ac.uk/proposal/5671

Thanks also to @JonathanGregory for your attention on this issue. I will come back to both of you soon.

Best wishes,
Ellie