Calving of icebergs based on ice shelf flux through static ice front

-This commit is the coupler contribution to calving of icebergs based
on the ice-shelf flux through a static ice-shelf front. This flux is
passed from MOM6 --> coupler --> SIS2 --> icebergs.
-To use, simply add calve_ice_shelf_bergs=True to the coupler nml (and
use the SIS2 and MOM6 commits that include ice-shelf calving).
-"Calving" based on frozen discharge from the land model can also be
used simultaneously, as long no cell has both nonzero
frozen-discharge-based and ice-shelf calving. For example,
land-discharge-based calving can be used for Greenland (without an
ice-sheet component) and ice-shelf calving for Antarctica
(with an ice-sheet component).
-Note that the data_override variable for ice-shelf calving is
Ocean_Ice_boundary%IS_calving to differentiate from the land-model
discharge-calving override Land_Ice_Boundary%calving.

full/coupler_main.F90

@@ -373,6 +373,7 @@ program coupler_main
   use ice_model_mod,           only: ice_data_type_chksum, ocn_ice_bnd_type_chksum
   use ice_model_mod,           only: atm_ice_bnd_type_chksum, lnd_ice_bnd_type_chksum
   use ice_model_mod,           only: unpack_ocean_ice_boundary, exchange_slow_to_fast_ice
+  use ice_model_mod,           only: unpack_ocean_ice_boundary_calved_shelf_bergs
   use ice_model_mod,           only: ice_model_fast_cleanup, unpack_land_ice_boundary
   use ice_model_mod,           only: exchange_fast_to_slow_ice, update_ice_model_slow
 
@@ -512,6 +513,8 @@ program coupler_main
   logical :: do_debug=.FALSE.       !< If .TRUE. print additional debugging messages.
   integer :: check_stocks = 0 ! -1: never 0: at end of run only n>0: every n coupled steps
   logical :: use_hyper_thread = .false.
+  logical :: calve_ice_shelf_bergs = .false. !< If true, flux through a static ice front is converted
+                                             !!to point bergs
 
   namelist /coupler_nml/ current_date, calendar, force_date_from_namelist,         &
                          months, days, hours, minutes, seconds, dt_cpld, dt_atmos, &
@@ -521,7 +524,8 @@ program coupler_main
                          concurrent, do_concurrent_radiation, use_lag_fluxes,      &
                          check_stocks, restart_interval, do_debug, do_chksum,      &
                          use_hyper_thread, concurrent_ice, slow_ice_with_ocean,    &
-                         do_endpoint_chksum, combined_ice_and_ocean
+                         do_endpoint_chksum, combined_ice_and_ocean,               &
+                         calve_ice_shelf_bergs
 
   integer :: initClock, mainClock, termClock
 
@@ -751,6 +755,10 @@ program coupler_main
         call fms_mpp_clock_begin(newClock10e)
         call exchange_fast_to_slow_ice(Ice)
         call fms_mpp_clock_end(newClock10e)
+        call fms_mpp_clock_begin(newClock10f)
+        if (Ice%slow_ice_pe .and. calve_ice_shelf_bergs) &
+          call unpack_ocean_ice_boundary_calved_shelf_bergs(Ice, Ocean_ice_boundary)
+        call fms_mpp_clock_end(newClock10f)
       endif
 
       if (Ice%fast_ice_pe) then
@@ -1004,6 +1012,10 @@ program coupler_main
         call fms_mpp_clock_begin(newClock10e)
         call exchange_fast_to_slow_ice(Ice)
         call fms_mpp_clock_end(newClock10e)
+        call fms_mpp_clock_begin(newClock10f)
+        if (Ice%slow_ice_pe .and. calve_ice_shelf_bergs) &
+          call unpack_ocean_ice_boundary_calved_shelf_bergs(Ice, Ocean_ice_boundary)
+        call fms_mpp_clock_end(newClock10f)
       endif
 
       !   ------ slow-ice model ------
@@ -1800,7 +1812,8 @@ subroutine coupler_init
       endif
       call fms_mpp_clock_begin(id_ocean_model_init)
       call ocean_model_init( Ocean, Ocean_state, Time_init, Time, &
-                             gas_fields_ocn=gas_fields_ocn  )
+                             gas_fields_ocn=gas_fields_ocn, &
+                             calve_ice_shelf_bergs=calve_ice_shelf_bergs)
       call fms_mpp_clock_end(id_ocean_model_init)
 
       if (concurrent) then

full/ice_ocean_flux_exchange.F90

@@ -88,13 +88,17 @@ subroutine ice_ocean_flux_exchange_init(Time, Ice, Ocean, Ocean_state, ice_ocean
     !frazil and sea_level are optional, if not present they should be nullified
     allocate( ocean_ice_boundary%frazil(is:ie,js:je) )
     allocate( ocean_ice_boundary%sea_level(is:ie,js:je) )
+    allocate( ocean_ice_boundary%calving(is:ie,js:je) )
+    allocate( ocean_ice_boundary%calving_hflx(is:ie,js:je) )
     ! initialize boundary fields for override experiments (mjh)
     ocean_ice_boundary%u=0.0
     ocean_ice_boundary%v=0.0
     ocean_ice_boundary%t=273.0
     ocean_ice_boundary%s=0.0
     ocean_ice_boundary%frazil=0.0
     ocean_ice_boundary%sea_level=0.0
+    ocean_ice_boundary%calving=0.0
+    ocean_ice_boundary%calving_hflx=0.0
 
     ! allocate fields for extra tracers in ocean_ice_boundary
     if (.not.fms_coupler_type_initialized(ocean_ice_boundary%fields)) &
@@ -221,7 +225,7 @@ end subroutine ice_ocean_flux_exchange_init
   !!        fprec = mass of frozen precipitation since last
   !!                  time step (Kg/m2)
   !!       runoff = mass of runoff since last time step (Kg/m2)
-  !!       runoff = mass of calving since last time step (Kg/m2)
+  !!       calving = mass of calving since last time step (Kg/m2)
   !!       p_surf = surface pressure (Pa)
   !! </pre>
   subroutine flux_ice_to_ocean ( Time, Ice, Ocean, Ice_Ocean_Boundary )
@@ -371,7 +375,9 @@ end subroutine flux_ice_to_ocean_finish
   !!        u_surf = zonal ocean current/ice motion (m/s)
   !!        v_surf = meridional ocean current/ice motion (m/s)
   !!        v_surf = meridional ocean current/ice motion (m/s)
-  !!       sea_lev = sea level used to drive ice accelerations (m)
+  !!        sea_lev = sea level used to drive ice accelerations (m)
+  !!        calving = ice-sheet calving flux to ocean (kg m-2 s-1)
+  !!        calving_hflx = heat flux associated with ice-sheet calving (W/m2)
   !! </pre>
   !!
   !! \throw FATAL, "Ocean_Ice_Boundary%xtype must be DIRECT or REDIST."
@@ -408,6 +414,23 @@ subroutine flux_ocean_to_ice ( Time, Ocean, Ice, Ocean_Ice_Boundary )
           endif
        endif
 
+       if( ASSOCIATED(Ocean_Ice_Boundary%calving) ) then
+          if(do_area_weighted_flux) then
+             Ocean_Ice_Boundary%calving = Ocean%calving * Ocean%area
+             call divide_by_area(data=Ocean_Ice_Boundary%calving, area=Ice%area)
+           else
+             Ocean_Ice_Boundary%calving = Ocean%calving
+          endif
+       endif
+       if( ASSOCIATED(Ocean_Ice_Boundary%calving_hflx) ) then
+          if(do_area_weighted_flux) then
+             Ocean_Ice_Boundary%calving_hflx = Ocean%calving_hflx * Ocean%area
+             call divide_by_area(data=Ocean_Ice_Boundary%calving_hflx, area=Ice%area)
+          else
+             Ocean_Ice_Boundary%calving_hflx = Ocean%calving_hflx
+          endif
+       endif
+
        ! Extra fluxes
        call fms_coupler_type_copy_data(Ocean%fields, Ocean_Ice_Boundary%fields)
 
@@ -438,6 +461,35 @@ subroutine flux_ocean_to_ice ( Time, Ocean, Ice, Ocean_Ice_Boundary )
           else
              call fms_mpp_domains_redistribute(Ocean%Domain, Ocean%frazil, Ice%slow_Domain_NH, Ocean_Ice_Boundary%frazil)
           endif
+        endif
+
+       if( ASSOCIATED(Ocean_Ice_Boundary%calving) ) then
+          if(do_area_weighted_flux) then
+             if (Ocean%is_ocean_pe) then
+               allocate(tmp(size(Ocean%area,1), size(Ocean%area,2)))
+               tmp(:,:) = Ocean%calving(:,:) * Ocean%area(:,:)
+             endif
+             call fms_mpp_domains_redistribute( Ocean%Domain, tmp, Ice%slow_Domain_NH, Ocean_Ice_Boundary%calving)
+             if (Ice%slow_ice_pe) &
+               call divide_by_area(data=Ocean_Ice_Boundary%calving, area=Ice%area)
+             if (Ocean%is_ocean_pe) deallocate(tmp)
+          else
+             call fms_mpp_domains_redistribute(Ocean%Domain, Ocean%calving, Ice%slow_Domain_NH, Ocean_Ice_Boundary%calving)
+          endif
+       endif
+       if( ASSOCIATED(Ocean_Ice_Boundary%calving_hflx) ) then
+          if(do_area_weighted_flux) then
+             if (Ocean%is_ocean_pe) then
+               allocate(tmp(size(Ocean%area,1), size(Ocean%area,2)))
+               tmp(:,:) = Ocean%calving_hflx(:,:) * Ocean%area(:,:)
+             endif
+             call fms_mpp_domains_redistribute( Ocean%Domain, tmp, Ice%slow_Domain_NH, Ocean_Ice_Boundary%calving_hflx)
+             if (Ice%slow_ice_pe) &
+               call divide_by_area(data=Ocean_Ice_Boundary%calving_hflx, area=Ice%area)
+             if (Ocean%is_ocean_pe) deallocate(tmp)
+          else
+             call fms_mpp_domains_redistribute(Ocean%Domain, Ocean%calving_hflx, Ice%slow_Domain_NH, Ocean_Ice_Boundary%calving_hflx)
+          endif
        endif
 
        ! Extra fluxes
@@ -469,6 +521,9 @@ subroutine flux_ocean_to_ice_finish( Time, Ice, Ocean_Ice_Boundary )
     call fms_data_override('ICE', 's',         Ocean_Ice_Boundary%s,         Time)
     call fms_data_override('ICE', 'frazil',    Ocean_Ice_Boundary%frazil,    Time)
     call fms_data_override('ICE', 'sea_level', Ocean_Ice_Boundary%sea_level, Time)
+    !Ice-shelf calving
+    call fms_data_override('ICE', 'IS_calving',      Ocean_Ice_Boundary%calving,      Time)
+    call fms_data_override('ICE', 'IS_calving_hflx', Ocean_Ice_Boundary%calving_hflx, Time)
     call fms_coupler_type_data_override('ICE', Ocean_Ice_Boundary%fields, Time)
 
     !  Perform diagnostic output for the ocean_ice_boundary fields