doc: correct Pstar units

[phil-blain]

PR checklist

• Short (1 sentence) summary of your PR:
  Correct units for Pstar in the doc.
• Developer(s):
  P. Blain
• Suggest PR reviewers from list in the column to the right.
• Please copy the PR test results link or provide a summary of testing completed below.
  No tests; doc changes only.
• How much do the PR code changes differ from the unmodified code?
  • bit for bit
  • different at roundoff level
  • more substantial
• Does this PR create or have dependencies on Icepack or any other models?
  • Yes doc: correct 'Pstar' units Icepack#325
  • No
• Does this PR add any new test cases?
  • Yes
  • No
• Is the documentation being updated? ("Documentation" includes information on the wiki or in the .rst files from doc/source/, which are used to create the online technical docs at https://readthedocs.org/projects/cice-consortium-cice/. A test build of the technical docs will be performed as part of the PR testing.)
  • Yes
  • No, does the documentation need to be updated at a later time?
    • Yes
    • No
• Please provide any additional information or relevant details below:

I checked the units for Pstar in Hibler's 1979 paper for #475, but it appears Hibler made a mistake in his table!
@JFLemieux73 pointed that to me offline.

[JFLemieux73]

Philippe,

When looking at the change I just saw that you write N/m\ :math:^2 while just above for k2 it is written as N/m\ :math:^3. Could you please correct one of them (I guess k2 is not done properly)?

[eclare108213]

I agree. We have P as N/m in other parts of the documentation (which should probably be changed because the value is hardwired in the doc)
https://cice-consortium-icepack.readthedocs.io/en/master/science_guide/sg_mechanical.html
(and if you look at eq 14 there, P has units of kg/s^2, which converts to N/m). Since Pstar includes a factor of thickness h, it needs to be N/m^2.

[phil-blain]

@JFLemieux73 I've fixed the RST syntax for k2.

@eclare108213 I fixed another occurence of "N/m" for Pstar in doc/source/cice_index.rst.

I went to the output of git grep --recurse-submodules 'N/m' and found two occurences in Icepack: the one you note in sg_mechanical.rst and another one in icepack/doc/source/icepack_index.rst:350.

I'll do a separate Icepack PR for these. Maybe we'll want to merge the Icepack PR so that this here PR can reference the new Icepack commit ? this would be cleaner, I think.

[eclare108213]

Fixing Icepack and merging it with this PR would be cleaner, yes, though not essential. Either way, thanks for doing this.

[phil-blain]

I've just pushed an additional commit updating Icepack to the latest master.

[apcraig]

I will run a full test suite with this PR. Now that icepack is updated, we should do that testing first.

[phil-blain]

thanks @apcraig. I agree.

[apcraig]

The test results are https://github.com/CICE-Consortium/Test-Results/wiki/cice_by_hash_forks#2e2cb0afe0fa8570d870eafec14c94d3f9d83eaa. This is fine. There are several regression failures due to the upgrade in Icepack, but this is expected. These come from code changes in CICE-Consortium/Icepack#320 and are documented clearly there.