Only add runoff tracer flux to surface flux if it has not already bee…

…n added

config_src/external/GFDL_ocean_BGC/generic_tracer_utils.F90

@@ -28,6 +28,7 @@ module g_tracer_utils
     character(len=fm_string_len) :: obc_src_file_name !< Boundary condition tracer source filename
     character(len=fm_string_len) :: obc_src_field_name !< Boundary condition tracer source fieldname
     integer :: src_var_record !< Unknown
+    logical :: runoff_added_to_stf = .false. !< Has flux in from runoff been added to stf?
     logical :: requires_src_info = .false. !< Unknown
     real    :: src_var_unit_conversion = 1.0 !< This factor depends on the tracer. Ask Jasmin
     real    :: src_var_valid_min = 0.0 !< Unknown

src/tracer/MOM_generic_tracer.F90

@@ -512,7 +512,7 @@ subroutine MOM_generic_tracer_column_physics(h_old, h_new, ea, eb, fluxes, Hml,
     !
     g_tracer=>CS%g_tracer_list
     do
-      if (_ALLOCATED(g_tracer%trunoff)) then
+      if (_ALLOCATED(g_tracer%trunoff) .and. (.NOT. g_tracer%runoff_added_to_stf)) then
         call g_tracer_get_alias(g_tracer,g_tracer_name)
         call g_tracer_get_pointer(g_tracer,g_tracer_name,'stf',   stf_array)
         call g_tracer_get_pointer(g_tracer,g_tracer_name,'trunoff',trunoff_array)
@@ -521,6 +521,7 @@ subroutine MOM_generic_tracer_column_physics(h_old, h_new, ea, eb, fluxes, Hml,
         runoff_tracer_flux_array(:,:) = trunoff_array(:,:) * &
                  US%RZ_T_to_kg_m2s*fluxes%lrunoff(:,:)
         stf_array = stf_array + runoff_tracer_flux_array
+        g_tracer%runoff_added_to_stf = .true.
       endif
 
       !traverse the linked list till hit NULL