Climate modules

Several methods are available for forcing the GRISLI model climatically. Each method corresponds to a module, but some modules can be used for a wide range of applications. Climate modules are stored in the SOURCES/Climate_modules directory.

1. climat_forcage

• Climate forcing with GCM climate and index time forcing file
• Absolute or anomaly in respect of a reference climate
• Read climate snapshot files
• Possibility of using any snapshot you like

Exemple of a param file to use climat_forcage for a deglaciation in anomaly :

!----------------------------------------------------------
! module climat_forcage
&clim_forcage
clim_ref_file = 'climato_monthly_t2m_era_int_precip_GPCP_1979-1999_hemin40.nc'
ntr           = 2
ttr_temp      = -21000, 0.
forcage_file  = 'IPSL-CM5A-LR-lgm-hemin40.nc', 'IPSL-CM5A-LR-piControl-hemin40.nc'
typerun       = 0
lapserate     = 0.007
rappact       = 0.11
filforc       = 'forcage-429k-quiquet-et-al_CP2013_glacial-index_Waelbroeck_AMOC.dat'
pertbmb       = 1
coefT         = 1.
coefbmb       = 10.
r_atmvar      = 0.25
/

Description of the individual parameters

• clim_ref_file : reference climate file (climatology) with monthly t2m and precipitation (rain + snow)
• ntr : number of climate GCM snapshot used
• ttr_temp : date corresponding to each snapshot
• forcage_file : GCM climate snapshot file with temperature, precipitation (monthly) and surface altitude
• typerun : 1 for steady state using snap 1, 2 for steady state using snap 2, 0 for transient.
• lapserate : vertical temperature gradient (°/m)
• rappact : precipitation ratio to temperature change
• filforc : name of file whith climatic perturbation through time used if typerun = 0
• pertbmb : 0 : basal melt under ice-shelves not modified, 1 : basal melt modified
• coeft : coeficient to modify temperature
• coefbmb : if we modify the bmelt (pertbmb=1), we read a perturbation (based on dD, insolation, etc.) and apply this coefficient
• r_atmvar : a ratio to account fast atmos variability between the 2 snapshots (in %: 0=>no fast var,1=>only fast var)

2. climat_InitMIP_years_perturb

Module used to run ISMIP simulations. Read an smb file with 1 or many time snapshots.

There are several ways of varying the surface mass balance:

• fixed over time => massb_time = 0
• apply anomalies (asmb and abmb initMIP simulations) => massb_time = 1
• interpolation between snapshots => massb_time = 2
• interpolation between snapshots + vertical interpolation (lapserate) => massb_time = 3

This module must be used with module no_ablation, since smb is read directly from forcing files.

!----------------------------------------------------------
! module climat_InitMIP_years_perturb_mod
&clim_smb_T_gen
smb_file           = reference climate smb file (kg/m2/an)
coef_smb_unit      = coef water to ice/year (1/910 or 1/918)
temp_annual_file   = reference climate mean annual temperature (°C)

!----------------------------------------------------------
! module climat_InitMIP_years_perturb_mod
&smb_anom_initMIP
file_smb_anom      = SMB anomalies from GCM
file_lapse         = lapse rate SMB and Tann (optionnal, used for greenland ISMIP scenarios)
coef_smb_anom_unit = coef water to ice/year (1/910 or 1/918)
nb_snap            = number of GCM snapshots
time_depart_snaps  = time of the first climate snapshot
massb_time         = 0:fixe, 1:anomalies, 2:interp snapshots, 3:snapsh+interp vert

3. climat_forcage_insolation

Module that allows GRISLI to be forced with a matrix of climate snapshots corresponding to different insolations, CO2 and ice sheet states.

!----------------------------------------------------------
! module climat-forcage-insolation_mod
&snap_forcage_mois_JB
filtr_t     = file with temperature 
filtr_p     = file with precip
Seuil_haut  = high surface threshold for each climate snapshot 
Seuil_bas   = low surface threshold for each snapshot
summorb     = average summer insolation for each set of orbital parameters
palier_ice  = ice surface of each climate snapshot
surf_ice    = topo file for each snapshot
palier_CO2  = CO2 level for each snapshot
orb_file    = files with orbital parameters over time 
co2_file    = file with co2 levels over time