Version 10 (modified by rlod, 19 months ago) (diff)

Name and subject of the action

Last edition: 11/30/20 18:04:30 by aumont

The PI is responsible to closely follow the progress of the action, and especially to contact NEMO project manager if the delay on preview (or review) are longer than the 2 weeks expected.

  1. Summary
  2. Preview
  3. Tests
  4. Review


Action Implementation of iceberg and ice shelf Fe source in PISCES
PI(S) Renaud Person
Digest see person et al. (2019), doi: 10.5194/bg-16-3583-2019
Dependencies coupling with feshwater fluxes from ice shelf and iceberg
Branch source:/NEMO/branches/2020/dev_r{REV}_{ACTION_NAME}
Previewer(s) O.Aumont, C. Éthe
Reviewer(s) O.Aumont, C. Éthe
Ticket #2443


Based on the development done with NEMO 3.6 of the representation of the missing external source of Fe from iceberg and ice shelf in the PISCES model


Describe flow chart of the changes in the code.
List the Fortran modules and subroutines to be created/edited/deleted.
Detailed list of new variables to be defined (including namelists),
give for each the chosen name and description wrt coding rules.

Fe is actualized according to the external sources of Fe from iceberg and ice shelf. A sediment content associated to a solubility fraction of sediment Fe is added to the freshwater fluxes of iceberg and ice shelf. For ice shelf, the parameterization of Mathiot et al. (2017) is used for the distribution of Fe throughout the water column. For iceberg, a homogeneous distribution until 120 m of depth is applied.

File dependency: feshwater fluxes from ice shelf and iceberg from observations and model climatology:


This file dependency didn’t exist for ORCA2 grid. I have build one but roughly interpolated. Another issue with the ORCA2 configuration is that the grid is not extended in the Antarctic. There is no representation of ice shelf cavities which are needed to model the distribution of freshwater flux under ice shelves with the parameterization of Mathiot et al. (2017) used in the present development.

Consequently, this external of source Fe will be disabled in the ORCA2 configuration.

Two options are possible to implement the development of the AIS Fe source:

  • Activation in PISCES: namelist_pisces (originally developed)
  • Activation in TOP: namelist_top

We opt for the generic solution by creating a trc_ais routine controllable in the TOP module and allowing to adjust the concentration of Fe and of other nutrients as well as DIC and Alkalinity in icebergs and ice shelves through a loop over all the biogeochemical tracers. This AIS tracers source will be activated with a boolean in the namelist_top named, for instance, ln_aistrc.

Starting point to create the trc_ais routine (3 subroutines):

  • trc_sbc (trc_bc?) for the structure
  • trc_ice for initialization, calling/reading of the 24 bgc tracers
  • p4zsed for interpolation and read freshwater flux from icebergs and ice shelves

To be added in the namelist_top

  • isffeinput: Fraction of bioavailable iron in ice shelves
  • icbfeinput: Fraction of bioavailable iron in iceberg
  • icbdepth: surface distribution (0) or throughout the water column until 120 m (1)

Do we use the same value fraction of bioavailable iron for both sources?

Warning: the isf source has to be activated in the namelist_cfg: parameter nn_isf >0

Orginally (activated in namelist_pisces_cfg with boolean ln_ironice)

Modified routines:

  • p4zsbc.F90
  • p4zsed.F90

Intermediate variables created to compute ziron variable:

  • zironberg: iron from iceberg freshwater flux
  • zironisf: iron from ice shelf freshwater flux

Documentation updates

Using previous parts, define the main changes to be done in the NEMO literature (manuals, guide, web pages, …).


Since the preview step must be completed before the PI starts the coding, the previewer(s) answers are expected to be completed within the two weeks after the PI has sent the request to the previewer(s).
Then an iterative process should take place between PI and previewer(s) in order to find a consensus

Possible bottlenecks:

  • the methodology
  • the flowchart and list of routines to be changed
  • the new list of variables wrt coding rules
  • the summary of updates in literature

Once an agreement has been reached, preview is ended and the PI can start the development into his branch.


Once the development is done, the PI should complete the tests section below and after ask the reviewers to start their review.

This part should contain the detailed results of SETTE tests (restartability and reproducibility for each of the reference configuration) and detailed results of restartability and reproducibility when the option is activated on specified configurations used for this test

Regular checks:

  • Can this change be shown to produce expected impact (option activated)?
  • Can this change be shown to have a null impact (option not activated)?
  • Results of the required bit comparability tests been run: are there no differences when activating the development?
  • If some differences appear, is reason for the change valid/understood?
  • If some differences appear, is the impact as expected on model configurations?
  • Is this change expected to preserve all diagnostics?
  • If no, is reason for the change valid/understood?
  • Are there significant changes in run time/memory?


A successful review is needed to schedule the merge of this development into the future NEMO release during next Merge Party (usually in November).


  • Is the proposed methodology now implemented?
  • Are the code changes in agreement with the flowchart defined at preview step?
  • Are the code changes in agreement with list of routines and variables as proposed at preview step?
    If, not, are the discrepancies acceptable?
  • Is the in-line documentation accurate and sufficient?
  • Do the code changes comply with NEMO coding standards?
  • Is the development documented with sufficient details for others to understand the impact of the change?
  • Is the project literature (manual, guide, web, …) now updated or completed following the proposed summary in preview section?


Is the review fully successful? If not, please indicate what is still missing

Once review is successful, the development must be scheduled for merge during next Merge Party Meeting.

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