diff --git a/src/Makefile b/src/Makefile
index 04a7607f..850f13e7 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -108,7 +108,7 @@ all : gnu
 
 .PHONY: gnu
 gnu:
-	$(MAKE) -f $(MAKE_DIR)/Makefile $(LIB_DIR)/libmarbl-gnu$(MPISUF).a USE_DEPS=TRUE FC=gfortran FCFLAGS="-Wall -Werror -O2 -ffree-form -J $(OBJ_DIR)/gnu$(MPISUF) -cpp" OBJ_DIR=$(OBJ_DIR)/gnu$(MPISUF) INC_DIR=$(INC_DIR)/gnu$(MPISUF)
+	$(MAKE) -f $(MAKE_DIR)/Makefile $(LIB_DIR)/libmarbl-gnu$(MPISUF).a USE_DEPS=TRUE FC=gfortran FCFLAGS="-Wall -Wextra -Wno-compare-reals -Werror -O2 -ffree-form -J $(OBJ_DIR)/gnu$(MPISUF) -cpp" OBJ_DIR=$(OBJ_DIR)/gnu$(MPISUF) INC_DIR=$(INC_DIR)/gnu$(MPISUF)
 
 .PHONY: intel
 intel:
diff --git a/src/marbl_diagnostics_mod.F90 b/src/marbl_diagnostics_mod.F90
index 12a88535..9ca6ba6f 100644
--- a/src/marbl_diagnostics_mod.F90
+++ b/src/marbl_diagnostics_mod.F90
@@ -4293,16 +4293,6 @@ subroutine marbl_diagnostics_set_surface_forcing( &
     type(marbl_surface_forcing_internal_type) , intent(in)    :: surface_forcing_internal
     type(marbl_diagnostics_type)              , intent(inout) :: surface_forcing_diags
 
-    !-----------------------------------------------------------------------
-    !  local variables
-    !-----------------------------------------------------------------------
-    character(len=*), parameter :: subname = 'marbl_diagnostics_mod:marbl_diagnostics_set_surface_forcing'
-    !-----------------------------------------------------------------------
-
-    !-----------------------------------------------------------------------
-    !  calculate gas flux quantities if necessary
-    !-----------------------------------------------------------------------
-
     associate(                                                                                  &
          ind_diag          => marbl_surface_forcing_diag_ind,                                   &
          ind_forc          => surface_forcing_ind,                                              &
@@ -4355,6 +4345,10 @@ subroutine marbl_diagnostics_set_surface_forcing( &
          docr_ind          => marbl_tracer_indices%docr_ind                                     &
          )
 
+    !-----------------------------------------------------------------------
+    !  calculate gas flux quantities if necessary
+    !-----------------------------------------------------------------------
+
     if (lflux_gas_o2 .or. lflux_gas_co2) then
 
        diags(ind_diag%ECOSYS_IFRAC)%field_2d(:)     = ifrac(:)
@@ -4577,6 +4571,7 @@ subroutine store_diagnostics_autotrophs(marbl_domain, &
     real(r8) :: autotrophC_weight(marbl_domain%km)
     real(r8) :: autotrophC_zint_100m
     real(r8) :: limterm(marbl_domain%km)
+    !-----------------------------------------------------------------------
 
     associate(                                     &
          diags   => marbl_interior_diags%diags,    &
@@ -5759,21 +5754,11 @@ subroutine store_diagnostics_ciso_surface_forcing( &
     real (r8), dimension(num_elements) , intent(in)    :: eps_dic_g_surf ! equilibrium fractionation between total DIC and gaseous CO2
     type(marbl_diagnostics_type)       , intent(inout) :: marbl_surface_forcing_diags
 
-    !-----------------------------------------------------------------------
-    !  local variables
-    !-----------------------------------------------------------------------
-    character(len=*), parameter :: subname = 'marbl_diagnostics_mod:store_diagnostics_ciso_surface_forcing'
-    !-----------------------------------------------------------------------
-
     associate(                                          &
          diags => marbl_surface_forcing_diags%diags,    &
          ind   => marbl_surface_forcing_diag_ind        &
          )
 
-    !-----------------------------------------------------------------------
-    !    Tavg variables
-    !-----------------------------------------------------------------------
-
     diags(ind%CISO_DI13C_GAS_FLUX)%field_2d(:) = FLUX13(:)
     diags(ind%CISO_DI14C_GAS_FLUX)%field_2d(:) = FLUX14(:)
 
diff --git a/src/marbl_init_mod.F90 b/src/marbl_init_mod.F90
index 0a284ed0..dca94bda 100644
--- a/src/marbl_init_mod.F90
+++ b/src/marbl_init_mod.F90
@@ -227,8 +227,6 @@ subroutine marbl_init_tracer_metadata(marbl_tracer_metadata, marbl_tracer_indice
     !  local variables
     !-----------------------------------------------------------------------
 
-    character(len=*), parameter :: subname = 'marbl_init_mod:marbl_init_tracer_metadata'
-
     integer (int_kind) :: n        ! index for looping over tracers
     integer (int_kind) :: zoo_ind  ! zooplankton functional group index
     integer (int_kind) :: auto_ind ! autotroph functional group index
diff --git a/src/marbl_interface.F90 b/src/marbl_interface.F90
index 0567bcc5..0c7fa332 100644
--- a/src/marbl_interface.F90
+++ b/src/marbl_interface.F90
@@ -736,8 +736,6 @@ subroutine inquire_settings_metadata_by_id(this, id, sname, lname, units, dataty
     character(len=*), optional,    intent(out)   :: sname, lname, units
     character(len=*), optional,    intent(out)   :: datatype
 
-    character(len=*), parameter :: subname = 'marbl_interface:inquire_settings_metadata_by_id'
-
     call this%settings%inquire_metadata(id,                  &
                                         sname    = sname,    &
                                         lname    = lname,    &
diff --git a/tests/driver_src/Makefile b/tests/driver_src/Makefile
index b8f805e5..dcca9854 100644
--- a/tests/driver_src/Makefile
+++ b/tests/driver_src/Makefile
@@ -125,7 +125,7 @@ all: gnu
 
 .PHONY: gnu
 gnu:
-	$(MAKE) -f $(MAKE_DIR)/Makefile $(EXE) COMP_NAME=gnu$(MPISUF) FC=gfortran FCFLAGS="-Wall -Werror -O2 -ffree-form -cpp" INC="-J $(OBJ_ROOT)/gnu$(MPISUF)" INC2="-J $(OBJ_ROOT)/gnu$(MPISUF)/driver"
+	$(MAKE) -f $(MAKE_DIR)/Makefile $(EXE) COMP_NAME=gnu$(MPISUF) FC=gfortran FCFLAGS="-Wall -Wextra -Wno-compare-reals -Werror -O2 -ffree-form -cpp" INC="-J $(OBJ_ROOT)/gnu$(MPISUF)" INC2="-J $(OBJ_ROOT)/gnu$(MPISUF)/driver"
 
 .PHONY: intel
 intel: