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2020WP/TOP-01_rlod_Antarctic_ice_Sheet_Fe_Source – NEMO
wiki:2020WP/TOP-01_rlod_Antarctic_ice_Sheet_Fe_Source

Version 15 (modified by rlod, 20 months ago) (diff)

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Summary

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

Description

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

Implementation

Representation of the external source of biogeochemical tracers from iceberg and ice shelf. For instance, for dissoved Fe, a sediment content associated to a solubility fraction of sediment Fe is added to the freshwater fluxes of iceberg and ice shelf. For iceberg, a homogeneous distribution of the biogeochemical tracers until 120 m of depth is applied. For ice shelf, the biogeochemical tracer content is distributed homogeneously following the representation of the isf freshwater flux of Mathiot et al. (2017) whether the under ice shelf cavities are open or not.

File dependency: feshwater fluxes from ice shelf and iceberg:

  • runoff-icb_DaiTrenberth_Depoorter_eORCA1_JD.nc
  • runoff-icb_DaiTrenberth_Depoorter_eORCA025_JD.nc

This file dependency didn’t exist for ORCA2 configuration as the grid is not extended in Antarctica. Thus, there is no representation of ice shelf cavities which are needed to model the distribution of freshwater flux under ice shelves with the parameterizations of Mathiot et al. (2017). Thus, this module can not be activated in ORCA2, the external source of BGC tracers from the Antarctic Ice Sheet is consequently disabled in this configuration.

  • Activation in TOP:

Creation of the trcais routine controllable in TOP module, which allows to adjust the concentration of Fe, for now, and of other biogeochemical tracers (potentially later) associated with iceberg and ice shelf freshwater fluxes through a loop over all the biogeochemical tracers. The AIS tracers source can be activated with a boolean in the namelist_top:

ln_trcais = .false. ! Antarctic Ice Sheet nutrient supply

!-----------------------------------------------------------------------

&namtrc_ais ! Representation of Antarctic Ice Sheet tracers supply

!-----------------------------------------------------------------------

rn_trafac(14) = 4.476e-07 ! ( 0.5e-3 / 55.85 * 0.05 )

!

nn_ais_tr = 1 ! tracer concentration in iceberg and ice shelf

  • 0 is for null concentrations
  • 1 for prescribed concentrations

rn_icbdep = 120. ! Mean underwater depth of iceberg (m)

Warning: the isf source has to be activated in the namelist_cfg:

ln_isf = .true.

then chose one of the two options for isf melt:

ln_isfcav_mlt = .false. or ln_isfpar_mlt = .true.

and activate runoff from icebergs

ln_rnf_icb = .true. ! freshwater flux from icebergs

created routine:

  • trcais.F90

List of modified routines:

  • nemogcm.F90
  • sbcrnf.F90
  • trc.F90
  • trcini.F90
  • trcnam.F90
  • trctrp.F90

Documentation updates

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