+Added an optional halo argument to geothermal

  Added an optional argument to geothermal that will cause it to work on an
extended region beyond the computational domain, along with a pass_var call on
the static geothermal heat flux to enable this to work properly.  All answers
are bitwise identical, but there is a new optional argument to a publicly
visible subroutines.

src/parameterizations/vertical/MOM_geothermal.F90

@@ -5,6 +5,7 @@ module MOM_geothermal
 
 use MOM_diag_mediator, only : post_data, register_diag_field, safe_alloc_ptr
 use MOM_diag_mediator, only : register_static_field, time_type, diag_ctrl
+use MOM_domains,             only : pass_var
 use MOM_error_handler, only : MOM_error, FATAL, WARNING
 use MOM_file_parser, only : get_param, log_param, log_version, param_file_type
 use MOM_io, only : MOM_read_data, slasher
@@ -44,7 +45,7 @@ module MOM_geothermal
 !! the partial derivative of the coordinate density with temperature is positive
 !! or very small, the layers are simply heated in place.  Any heat that can not
 !! be applied to the ocean is returned (WHERE)?
-subroutine geothermal(h, tv, dt, ea, eb, G, GV, CS)
+subroutine geothermal(h, tv, dt, ea, eb, G, GV, CS, halo)
   type(ocean_grid_type),                    intent(inout) :: G  !< The ocean's grid structure.
   type(verticalGrid_type),                  intent(in)    :: GV !< The ocean's vertical grid
                                                                 !! structure.
@@ -69,6 +70,7 @@ subroutine geothermal(h, tv, dt, ea, eb, G, GV, CS)
   type(geothermal_CS),                      pointer       :: CS !< The control structure returned by
                                                                 !! a previous call to
                                                                 !! geothermal_init.
+  integer,                        optional, intent(in)    :: halo !< Halo width over which to work
   ! Local variables
   real, dimension(SZI_(G)) :: &
     heat_rem,  & ! remaining heat (H * degC)
@@ -105,6 +107,9 @@ subroutine geothermal(h, tv, dt, ea, eb, G, GV, CS)
 
 
   is = G%isc ; ie = G%iec ; js = G%jsc ; je = G%jec ; nz = G%ke
+  if (present(halo)) then
+    is = G%isc-halo ; ie = G%iec+halo ; js = G%jsc-halo ; je = G%jec+halo
+  endif
 
   if (.not. associated(CS)) call MOM_error(FATAL, "MOM_geothermal: "//&
          "Module must be initialized before it is used.")
@@ -377,6 +382,7 @@ subroutine geothermal_init(Time, G, param_file, diag, CS)
       CS%geo_heat(i,j) = G%mask2dT(i,j) * scale
     enddo ; enddo
   endif
+  call pass_var(CS%geo_heat, G%domain)
 
   ! post the static geothermal heating field
   id = register_static_field('ocean_model', 'geo_heat', diag%axesT1,   &