Answer changes were due to aggressive compiler optimizations on works…

…tation. adding -fp-model precise and -fp-model source now leaves answers unchanged in a small suit of test cases. Some typos were fixed, but otherwise this code should work fine.

src/core/MOM.F90

@@ -213,7 +213,7 @@ module MOM
   type(time_type) :: Z_diag_interval !< amount of time between calculating Z-space diagnostics
   type(time_type) :: Z_diag_time     !< next time to compute Z-space diagnostics
   type(time_type), pointer :: Time   !< pointer to ocean clock
-  real :: rel_time = 0.0             !< relative time (sec) sinc.e start of current execution
+  real :: rel_time = 0.0             !< relative time (sec) since start of current execution
   real :: dtbt_reset_period          !< The time interval in seconds between dynamic
                                      !! recalculation of the barotropic time step.  If
                                      !! this is negative, it is never calculated, and
@@ -1002,7 +1002,6 @@ subroutine step_MOM(fluxes, state, Time_start, time_interval, CS)
 
       call cpu_clock_begin(id_clock_tracer)
 
-      ! Post fields used for offline tracer model
       call advect_tracer(h, CS%uhtr, CS%vhtr, CS%OBC, CS%dt_trans, G, GV, &
                          CS%tracer_adv_CSp, CS%tracer_Reg)
       call tracer_hordiff(h, CS%dt_trans, CS%MEKE, CS%VarMix, G, GV, &

src/parameterizations/vertical/MOM_diabatic_driver.F90

@@ -256,8 +256,7 @@ subroutine diabatic(u, v, h, tv, fluxes, visc, ADp, CDp, dt, G, GV, CS)
     dSV_dS, &    ! and salinity in m^3/(kg K) and m^3/(kg ppt).
     cTKE,   &    ! convective TKE requirements for each layer in J/m^2.
     u_h,    &    ! zonal and meridional velocities at thickness points after
-    v_h,    &    ! entrainment (m/s)
-    hloss_boundary ! Change in layer thickness because of freshwater fluxes at the surfac
+    v_h          ! entrainment (m/s)
 
   real, dimension(SZI_(G),SZJ_(G),CS%nMode) :: &
     cn       ! baroclinic gravity wave speeds (formerly cg1 - BDM)
@@ -1143,7 +1142,7 @@ subroutine diabatic(u, v, h, tv, fluxes, visc, ADp, CDp, dt, G, GV, CS)
     if (CS%useALEalgorithm) then
     ! For passive tracers, the changes in thickness due to boundary fluxes has yet to be applied
     ! so hold should be h_orig
-      call call_tracer_column_fns(h_prebound, h, eatr, ebtr, fluxes, dt, G, GV, tv, &
+      call call_tracer_column_fns(h_prebound, h, ea, eb, fluxes, dt, G, GV, tv, &
                                 CS%optics, CS%tracer_flow_CSp, CS%debug, &
                                 evap_CFL_limit = CS%diabatic_aux_CSp%evap_CFL_limit, &
                                 minimum_forcing_depth = CS%diabatic_aux_CSp%minimum_forcing_depth)
@@ -1186,7 +1185,7 @@ subroutine diabatic(u, v, h, tv, fluxes, visc, ADp, CDp, dt, G, GV, CS)
   else
     if (CS%useALEalgorithm) then
     ! For passive tracers, the changes in thickness due to boundary fluxes has yet to be applied
-      call call_tracer_column_fns(h_prebound, h, ea, eb, fluxes, dt, G, GV, tv, &
+      call call_tracer_column_fns(h_prebound, h, eatr, ebtr, fluxes, dt, G, GV, tv, &
                                   CS%optics, CS%tracer_flow_CSp, CS%debug, &
                                   evap_CFL_limit = CS%diabatic_aux_CSp%evap_CFL_limit, &
                                   minimum_forcing_depth = CS%diabatic_aux_CSp%minimum_forcing_depth)

src/tracer/MOM_tracer_hor_diff.F90

@@ -103,8 +103,7 @@ subroutine tracer_hordiff(h, dt, MEKE, VarMix, G, GV, CS, Reg, tv, do_online_fla
   logical,                           optional             :: do_online_flag
   real, dimension(SZIB_(G),SZJ_(G)), optional, intent(in) :: read_khdt_x
   real, dimension(SZI_(G),SZJB_(G)), optional, intent(in) :: read_khdt_y
-
-  logical                                                 :: do_online = .true.
+
 
   real, dimension(SZI_(G),SZJ_(G)) :: &
     Ihdxdy, &     ! The inverse of the volume or mass of fluid in a layer in a
@@ -128,7 +127,7 @@ subroutine tracer_hordiff(h, dt, MEKE, VarMix, G, GV, CS, Reg, tv, do_online_fla
     Kh_v          ! Tracer mixing coefficient at u-points, in m2 s-1.
 
   real :: max_CFL ! The global maximum of the diffusive CFL number.
-  logical :: use_VarMix, Resoln_scaled
+  logical :: use_VarMix, Resoln_scaled, do_online
   integer :: i, j, k, m, is, ie, js, je, nz, ntr, itt, num_itts
   real :: I_numitts  ! The inverse of the number of iterations, num_itts.
   real :: scale      ! The fraction of khdt_x or khdt_y that is applied in this
@@ -143,6 +142,7 @@ subroutine tracer_hordiff(h, dt, MEKE, VarMix, G, GV, CS, Reg, tv, do_online_fla
 
   is = G%isc ; ie = G%iec ; js = G%jsc ; je = G%jec ; nz = GV%ke
 
+  do_online = .true.
   if (present(do_online_flag)) do_online = do_online_flag
 
   if (.not. associated(CS)) call MOM_error(FATAL, "MOM_tracer_hor_diff: "// &