Adds new ocean to ice coupling fields for frazil ice formation by njeffery · Pull Request #460 · E3SM-Project/Omega

njeffery · 2026-07-06T20:03:10Z

Allows for the ocean model to compute the accumulated frazil mass, salt mass, and energy,
and passes to the sea ice model If mpas-seaice option, config_frazil_coupling_type = “omega-fluxes”.

Fioo_Frazils – total accumulated frazil salt mass per time
Fioo_Frazilh – total accumulated frazil energy per time (defined as positive to be consistent with ‘q’ the sea ice potential)

The new implementation has a requirement that the new frazil salinity be greater than 0.1 ppt.

Works with icepack https://github.com/E3SM-Project/Icepack/tree/njeffery/omega-coupling-frazil in E3SM-Project/Icepack#43

Includes updates from @erinethomas and @karapeterson (https://github.com/erinethomas/E3SM/tree/omega/ice-coupling)

Tested in mpas-ocean and confirmed BFB for default config_frazil_coupling_type = “external”
Stealth.

…i_cpl_indices.F,seq_flds_mod.F90

add index_x2i_Fioo_frazilh (frazil heat flux from ocean) add index_x2i_Fioi_frazil (frazil mass flux from sea ice) add index_x2i_Fioi_frazils (frazil salt flux from sea ice) add index_x2i_Fioi_frazilh (frazil heat flux from sea ice) All added to mpassi_cpl_indices.F and seq_flds_mod.F90. Fioi_frazil and Fioi_frazils added to ice_comp_mct.F

Updates Icepack submodule to frazil coupling branch Adds ocean-ice coupling fields: frazil salt flux (Fioo_frazils) frazil enthalpy flux (Fioo_frazilh) defined consistent with freezingMeltPotential To use, set config_frazil_coupling_type to ‘omega-fluxes’ Backwards compatible with mpas-ocean for config_frazil_coupling_type = ‘external’ Stealth

Sea ice initialize now allows for the config_frazil_coupling_type option: "omega-fluxes"

Sea ice initialize NOW allows for config_frazil_coupling_type option: “omega-fluxes”

Removes double counting of frazil energy in coupler budget. Corrects possible but in temperature tendency of frazil melt. nBFB

Adds optional formulation in frazil.

Revert to original formulation with comments.

njeffery · 2026-07-06T20:14:31Z

Test simulations here: https://e3sm.atlassian.net/wiki/spaces/pd/pages/6409257086/05282026.v3.GMPAS.frazil-omega-fluxes.pm-cpu

njeffery · 2026-07-06T20:20:38Z

And here: https://e3sm.atlassian.net/wiki/spaces/pd/pages/6450512447/06222026.v3.GMPAS.frazil-omega-fluxes4.pm-cpu

darincomeau · 2026-07-29T18:33:21Z

      !$omp         freezingEnergy, meltingEnergy, frazilSalinity, newFrazilIceThickness, &
      !$omp         newThicknessWeightedSaltContent, meltedFrazilIceThickness, &
-      !$omp         meltedThicknessWeightedSaltContent)
+      !$omp         meltedThicknessWeightedSaltContent, newFrazilEnergy, meltedFrazilEnergy)


typo here? is this line meant to end with ", &" rather than ")"?

also newFrazilEnergy appears twice here, this line and next.

njeffery · 2026-07-29T19:02:38Z

@darincomeau : Thanks for catching that!

darincomeau · 2026-07-29T20:35:50Z

With the above two fixes, and using E3SM-Project/Icepack#43, this passes e3sm_cryo_developer. Also passes

SMS_D_Ld1.TL319_IcoswISC30E3r5.GMPAS-JRA1p5-DIB-PISMF.chrysalis_intel.mpaso-jra_1958

with config_frazil_coupling_type = 'omega-fluxes' in user_nl_mpassi.

karapeterson

The PR looks good and builds and runs successfully after the changes that Darin suggested. The final change that needs to be committed before approval is to remove the extra 'newFrazilEnergy' on line 561 of mpas_ocn_frazil_forcing.F.

https://github.com/E3SM-Project/Omega/pull/460/changes#diff-aebe6a7f54022252cfe51bc70ac05a31798f2a92b02829d791f66cd8911647c6R561

Copilot

Pull request overview

This PR extends the MPAS-Ocean ⇄ MPAS-Seaice coupling to support an “omega-fluxes”
mode for frazil formation, adding separate coupling fields for frazil mass, salt, and
energy/enthalpy fluxes and updating driver diagnostics/metadata accordingly.

Changes:

Add new coupler fields for frazil salt and heat/enthalpy fluxes (ocean→ice) and frazil
mass/salt/heat fluxes (ice→ocean), including metadata registration in both MCT and
MOAB drivers.
Extend MPAS-Seaice coupling pools/Registry and driver import/export logic to pass and
use frazil fluxes when config_frazil_coupling_type="omega-fluxes".
Accumulate and export frazil latent energy in MPAS-Ocean and update conservation/
diagnostic bookkeeping.

Reviewed changes

Copilot reviewed 18 out of 18 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
driver-moab/shr/seq_flds_mod.F90	Registers new frazil coupling fields/metadata for MOAB driver.
driver-mct/shr/seq_flds_mod.F90	Registers new frazil coupling fields/metadata for MCT driver.
driver-mct/main/seq_diag_mct.F90	Adds new budget terms for frazil heat/salt and prints salt budgets.
components/mpas-seaice/src/shared/mpas_seaice_initialize.F	Allows `omega-fluxes` as a valid frazil coupling type.
components/mpas-seaice/src/shared/mpas_seaice_icepack.F	Passes new frazil flux arrays into Icepack column call.
components/mpas-seaice/src/Registry.xml	Adds new ocean-coupling variables and exposes the new coupling type.
components/mpas-seaice/driver/mpassi_cpl_indices.F	Adds new MCT coupling indices for frazil flux fields.
components/mpas-seaice/driver/ice_comp_mct.F	Imports ocean frazil fluxes; exports ice-side frazil adjustment fluxes.
components/mpas-seaice/cime_config/buildnml	Adds new coupling vars to generated stream/IO lists.
components/mpas-seaice/bld/namelist_files/namelist_definition_mpassi.xml	Documents `omega-fluxes` as a valid namelist option.
components/mpas-ocean/src/shared/mpas_ocn_frazil_forcing.F	Accumulates frazil latent energy alongside mass/salinity.
components/mpas-ocean/src/Registry.xml	Adds `accumulatedFrazilIceEnergy` state variable.
components/mpas-ocean/src/analysis_members/Registry_conservation_check.xml	Fixes a typo in frazil heat-flux description text.
components/mpas-ocean/src/analysis_members/mpas_ocn_conservation_check.F	Updates conservation check to use accumulated frazil energy.
components/mpas-ocean/driver/ocn_comp_mct.F	Exports frazil salt and heat/enthalpy fluxes to the coupler.
components/mpas-ocean/driver/mpaso_cpl_indices.F	Adds new coupling indices for frazil salt/heat flux exports.

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           freezingMeltingPotential(i) = x2i_i(index_x2i_Fioo_q, n)

+           frazilSaltFlux(i)           = 0.0_RKIND
+           frazilEnthalpyFlux(i)       = 0.0_RKIND
+           frazilMassAdjust(i)         = 0.0_RKIND
+


+                write(logunit,FA1)    '   *SUM*'   ,sum(dataGpr(f_s:f_s_end,ica,ip)),sum(dataGpr(f_s:f_s_end,icl,ip)), &
+                     sum(dataGpr(f_s:f_s_end,icn,ip)),sum(dataGpr(f_s:f_s_end,ics,ip)),sum(dataGpr(f_s:f_s_end,ico,ip)), &
+                     sum(dataGpr(f_s:f_s_end,ica,ip))+sum(dataGpr(f_s:f_s_end,icl,ip))+ &
+                     sum(dataGpr(f_s:f_s_end,icn,ip))+sum(dataGpr(f_s:f_s_end,ics,ip))+sum(dataGpr(f_s:f_s_end,ico,ip))


+    attname  = 'Fioo_frazils'
+    call metadata_set(attname, longname, stdname, units)
+
+    ! Ocean frazil head flux


+    ! Ocean frazil salt production
+    call seq_flds_add(o2x_fluxes,"Fioo_frazils")
+    call seq_flds_add(x2i_fluxes,"Fioo_frazils")
+    longname = 'Ocean frazil salt production'
+    stdname  = 'ocean_frazil_salt_production'


1. Initialized frazilMassFlux to 0 for SOM 2. Corrected indexing of component-level salt budget sum 3. Type in comment 4. Corrected definition of Fioo_frazils in MOAB to be consistent with mct

karapeterson · 2026-08-18T18:09:18Z

Adding a note that a follow-up pull request will add a scaling factor in driver-mct/main/seq_diag_mct.F90, corresponding to the following line in E3SM master:

https://github.com/E3SM-Project/E3SM/blob/4314dbdcf4fd4f220dd7edb2cc83bf3621344bf8/driver-mct/main/seq_diag_mct.F90#L1998

erinethomas and others added 13 commits May 27, 2026 09:40

add index_x2i_Fioo_frazils (frazil salt flux) to ice_comp_mct.F,mpass…

eccb199

…i_cpl_indices.F,seq_flds_mod.F90

adding o2x_Fioo_frazilh/o2x_Fioo_frazils to mpaso

69be928

Add budgeting in mct coupler for new coupling fields.

32602c0

Fix bugs leading to build errors.

05142f5

Update sea ice config checks

9d12c7b

Sea ice initialize now allows for the config_frazil_coupling_type option: "omega-fluxes"

Corrects update sea ice config options

51b99ec

Sea ice initialize NOW allows for config_frazil_coupling_type option: “omega-fluxes”

Fixes salt flux units error

76e673e

Make frazil energy consistent with the ocean energy change

b4d14ac

Removes double counting of frazil energy in coupler budget. Corrects possible but in temperature tendency of frazil melt. nBFB

fixed type introduced in last commit

cd9595f

Corrections to ensure BFB

02ea1b6

Adds optional formulation in frazil.

Clean up ocean frazil routine

8630cdf

Revert to original formulation with comments.

njeffery requested review from alicebarthel, darincomeau, erinethomas, karapeterson and proteanplanet July 6, 2026 20:03

njeffery assigned jonbob Jul 6, 2026

njeffery added the enhancement New feature or request label Jul 6, 2026

darincomeau reviewed Jul 29, 2026

View reviewed changes

corrects typo in frazil routine

9ae18ee

darincomeau force-pushed the seaice-coupling branch from 978e56f to 0ae578b Compare August 10, 2026 22:19

karapeterson requested changes Aug 13, 2026

View reviewed changes

Remove redundant newFrazilEnergy

1c36669

njeffery requested a lite review from Copilot August 14, 2026 14:54

Copilot started reviewing on behalf of njeffery August 14, 2026 14:55 View session

Copilot AI reviewed Aug 14, 2026

View reviewed changes

Added copilot suggestions

58b8031

1. Initialized frazilMassFlux to 0 for SOM 2. Corrected indexing of component-level salt budget sum 3. Type in comment 4. Corrected definition of Fioo_frazils in MOAB to be consistent with mct

njeffery marked this pull request as ready for review August 18, 2026 16:21

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Adds new ocean to ice coupling fields for frazil ice formation - #460

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