Changed ice-shelf calving so that it is no longer cumulative over tim…

…e steps, which seems to have been an error that caused too many bergs to calve. Also fixed potential sign error for ice shelf calving hflx and unit scaling for ice shelf calving.

src/ice_shelf/MOM_ice_shelf.F90

@@ -854,7 +854,7 @@ subroutine ice_sheet_calving_to_ocean_sfc(CS,US,calving,calving_hflx)
   ISS => CS%ISS
   is = G%isc ; ie = G%iec ; js = G%jsc ; je = G%jec
 
-  calving = US%RZ_to_kg_m2 * ISS%calving(is:ie, js:je)
+  calving = US%RZ_T_to_kg_m2s * ISS%calving(is:ie,js:je)
   calving_hflx = US%QRZ_T_to_W_m2 * ISS%calving_hflx(is:ie,js:je)
 
   CS%calve_ice_shelf_bergs=.true.

src/ice_shelf/MOM_ice_shelf_dynamics.F90

@@ -1179,19 +1179,12 @@ subroutine ice_shelf_advect(CS, ISS, G, time_step, Time, calve_ice_shelf_bergs)
     call shelf_advance_front(CS, ISS, G, ISS%hmask, uh_ice, vh_ice)
     !add mass of the partially-filled cells to calving field, which is used to initialize icebergs
     !Then, remove the partially-filled cells from the ice shelf
-    !Note that the ocean_public_type calving and calving_hflx point
-    !to ISS%calving and ISS%calving_hflx, repectively
     do j=jsc,jec; do i=isc,iec
       if (ISS%hmask(i,j)==2) then
-        ISS%calving(i,j) = ISS%calving(i,j) + &
-          ISS%h_shelf(i,j) * ISS%area_shelf_h(i,j) * CS%density_ice / (G%areaT(i,j) * time_step) !kg/m2s
-        !is this correct (which Cp and T do you use?) See river definition of calving_hflx?
-        !see MOM_forcing_type.F90...why use heat capacity of seawater there.
-        !here, we use Cp_ice of freshwater, and dT is the shelf temperature (maybe should be
-        !shelf temperature - local seawater temperature?)
-        ISS%calving_hflx(i,j) = ISS%calving_hflx(i,j) + &
-          CS%Cp_ice * ISS%h_shelf(i,j) * ISS%area_shelf_h(i,j) * &
-          CS%density_ice * abs(CS%t_shelf(i,j)) / G%areaT(i,j)  !W/m2
+        ISS%calving(i,j) = ISS%h_shelf(i,j) * ISS%area_shelf_h(i,j) * &
+                           CS%density_ice / (G%areaT(i,j) * time_step)
+        ISS%calving_hflx(i,j) = CS%Cp_ice * ISS%h_shelf(i,j) * ISS%area_shelf_h(i,j) * &
+                                CS%density_ice * CS%t_shelf(i,j) / G%areaT(i,j)
         ISS%h_shelf(i,j) = 0.0; ISS%area_shelf_h(i,j) = 0.0; ISS%hmask(i,j) = 0.0
       endif
     enddo; enddo

src/ice_shelf/MOM_ice_shelf_state.F90

@@ -51,7 +51,7 @@ module MOM_ice_shelf_state
 
     !only active when calve_point_bergs_from_static_shelf_front=.true.:
     calving => NULL(), &       !< The mass per unit area of the ice shelf to convert to
-                               !!bergs [R Z ~> kg m-2].
+                               !!bergs [RZ_T ~> kg m-2 s-1].
     calving_hflx => NULL()     !< Calving heat flux [Q R Z T-1 ~> W m-2].
 end type ice_shelf_state