Version 3 (modified by mathiot, 7 years ago) (diff)

Last edited Timestamp?


Author : Mathiot

ticket : #1331

Branch : dev_r4650_UKMO2_ice_shelves


Description

Dynamics for the top layer beneath the ice shelves:

  • top partial step
  • top friction (same option as for the bottom friction)
  • Correction of the divergence locally (as for runoff fresh water flux)

Thermodynamics used to compute the melt rate:

  • ISOMIP formulation (2 equation formulation)
  • 3 equation formulation (Jenkins et al. 1991)
  • Forcing mode (prescribed melt rate) is available.
  • Losh top boundary layer (Losch et al., 2008)

Validation configuration: ISOMIP

ISOMIP is a closed rectangular basin of uniform depth 900 m, spanning 15° of longitude, and latitudes 80° South to 70° South. The whole basin is covered with an ice shelf, with the ice draft rising linearly from 700 m at 80° South to 200 m at 76° South, and remaining constant at 200 m from 76° South to 70° South. The geometry is uniform in the east-west direction. All the model setup and geometry is fully described in J.R. Hunter, 2006.

Bibliography:

  • Hunter, J.R.: Specification for test models of ice shelf cavities, technical report, Antarctic Climate & Ecosystems Cooperative Research centre, version 7, 2006.
  • Jenkins, A., Hellmer, H.H. and D.H. Holland: The Role of Meltwater Advection in the Formulation of Conservative Boundary Conditions at an Ice–Ocean Interface, Journal of physical oceanography, 31, 2001.
  • Losch, M. Modeling ice shelf cavities in a z coordinate ocean general circulation model Journal of Geophysical Research: Oceans, 2008, 113

Reviewers:

  • System reviewer: Andrew Coward
  • Science reviewer: Gurvan Madec

Testing

Testing could consider (where appropriate) other configurations in addition to NVTK].

NVTK Tested'''YES/NO'''
Other model configurations'''YES/NO'''
Processor configurations tested[ Enter processor configs tested here ]
If adding new functionality please confirm that the
New code doesn't change results when it is switched off
and ''works'' when switched on
'''YES/NO/NA'''

(Answering UNSURE is likely to generate further questions from reviewers.)

'Please add further summary details here'

  • Processor configurations tested
  • etc——

Bit Comparability

Does this change preserve answers in your tested standard configurations (to the last bit) ?'''YES/NO '''
Does this change bit compare across various processor configurations. (1xM, Nx1 and MxN are recommended)'''YES/NO'''
Is this change expected to preserve answers in all possible model configurations?'''YES/NO'''
Is this change expected to preserve all diagnostics?
,,''Preserving answers in model runs does not necessarily imply preserved diagnostics. ''
'''YES/NO'''

If you answered '''NO''' to any of the above, please provide further details:

  • Which routine(s) are causing the difference?
  • Why the changes are not protected by a logical switch or new section-version
  • What is needed to achieve regression with the previous model release (e.g. a regression branch, hand-edits etc). If this is not possible, explain why not.
  • What do you expect to see occur in the test harness jobs?
  • Which diagnostics have you altered and why have they changed?Please add details here……..

System Changes

Does your change alter namelists? YES
Does your change require a change in compiler options? NO

If any of these apply, please document the changes required here……. Namelist changes:

 !-----------------------------------------------------------------------
 &namsbc        !   Surface Boundary Condition (surface module)
 !-----------------------------------------------------------------------
   nn_isf      = 1         !  0=no isf / 1 = presence of ISF / 2 = bg03 parametrisation / 3 = rnf file for isf / 4 = prescribed melt rate 
 /
 !-----------------------------------------------------------------------
 &namsbc_isf    !  Top boundary layer (ISF)
 !-----------------------------------------------------------------------
 !              ! file name ! frequency (hours) ! variable ! time interpol. !  clim   ! 'yearly'/ ! weights  ! rotation !
 !              !           !  (if <0  months)  !   name   !    (logical)   !  (T/F)  ! 'monthly' ! filename ! pairing  !
 ! nn_isf == 4
   sn_qisf      = 'rnfisf' ,         -12      ,'sohflisf',    .false.      , .true.  , 'yearly'  ,  ''      ,   ''
   sn_fwfisf    = 'rnfisf' ,         -12      ,'sowflisf',    .false.      , .true.  , 'yearly'  ,  ''      ,   ''
 ! nn_isf == 3
   sn_rnfisf    = 'runoffs' ,         -12      ,'sofwfisf',    .false.      , .true.  , 'yearly'  ,  ''      ,   ''
 ! nn_isf == 2 and 3
   sn_depmax_isf = 'runoffs' ,       -12        ,'sozisfmax' ,   .false.  , .true.  , 'yearly'  ,  ''      ,   ''
   sn_depmin_isf = 'runoffs' ,       -12        ,'sozisfmin' ,   .false.  , .true.  , 'yearly'  ,  ''      ,   ''
 ! nn_isf == 2
   sn_Leff_isf = 'rnfisf' ,       0          ,'Leff'         ,   .false.  , .true.  , 'yearly'  ,  ''      ,   ''
 ! for all case
   ln_divisf   = .true.  ! apply isf melting as a mass flux or in the salinity trend. (maybe I should remove this option as for runoff?)
 ! only for nn_isf = 1 or 2
   rn_gammat0  = 1.0e-4   ! gammat coefficient used in blk formula
   rn_gammas0  = 1.0e-4   ! gammas coefficient used in blk formula
 ! only for nn_isf = 1
   nn_isfblk   =  1       ! 1 ISOMIP ; 2 conservative (3 equation formulation, Jenkins et al. 1991 ??)
   rn_hisf_tbl =  30.      ! thickness of the top boundary layer           (Losh et al. 2008)
                          ! 0 => thickness of the tbl = thickness of the first wet cell
   ln_conserve = .true.   ! conservative case (take into account meltwater advection)
   nn_gammablk = 0        ! 0 = cst Gammat (= gammat/s)
                          ! 1 = velocity dependend Gamma (u* * gammat/s)  (Jenkins et al. 2010)
                          !     if you want to keep the cd as in global config, adjust rn_gammat0 to compensate
                          ! 2 = velocity and stability dependent Gamma    Holland et al. 1999
/
!-----------------------------------------------------------------------
&nambfr        !   bottom/top friction
!-----------------------------------------------------------------------
   rn_tfri1    =    4.e-4  !  top drag coefficient (linear case)
   rn_tfri2    =    2.5e-3 !  top drag coefficient (non linear case). Minimum coeft if ln_loglayer=T
   rn_tfri2_max =   1.e-1  !  max. top drag coefficient (non linear case and ln_loglayer=T)
   rn_tfeb2    =    0.0    !  top turbulent kinetic energy background  (m2/s2)
   rn_tfrz0    =    3.e-3  !  top roughness [m] if ln_loglayer=T
   ln_tfr2d    = .false.   !  horizontal variation of the top friction coef (read a 2D mask file )
   rn_tfrien   =    50.    !  local multiplying factor of tfr (ln_tfr2d=T)
/

Resources

''Please ''summarize'' any changes in runtime or memory use caused by this change……''


IPR issues

Has the code been wholly (100%) produced by NEMO developers staff working exclusively on NEMO?'''YES/ NO '''

If No:

  • Identify the collaboration agreement details
  • Ensure the code routine header is in accordance with the agreement, (Copyright/Redistribution? etc).Add further details here if required……….