diff --git a/components/mpas-ocean/bld/build-namelist b/components/mpas-ocean/bld/build-namelist
index e35c24f8be26..c8e1c1e3a7a4 100755
--- a/components/mpas-ocean/bld/build-namelist
+++ b/components/mpas-ocean/bld/build-namelist
@@ -616,6 +616,8 @@ add_default($nl, 'config_use_cvmix');
add_default($nl, 'config_cvmix_prandtl_number');
add_default($nl, 'config_cvmix_background_scheme');
add_default($nl, 'config_cvmix_background_diffusion');
+add_default($nl, 'config_cvmix_background_diffusion_passive');
+add_default($nl, 'config_cvmix_background_diffusion_passive_enable');
add_default($nl, 'config_cvmix_background_viscosity');
add_default($nl, 'config_cvmix_BryanLewis_bl1');
add_default($nl, 'config_cvmix_BryanLewis_bl2');
diff --git a/components/mpas-ocean/bld/build-namelist-section b/components/mpas-ocean/bld/build-namelist-section
index 7acfc0c82307..b202284f3005 100644
--- a/components/mpas-ocean/bld/build-namelist-section
+++ b/components/mpas-ocean/bld/build-namelist-section
@@ -155,6 +155,8 @@ add_default($nl, 'config_use_cvmix');
add_default($nl, 'config_cvmix_prandtl_number');
add_default($nl, 'config_cvmix_background_scheme');
add_default($nl, 'config_cvmix_background_diffusion');
+add_default($nl, 'config_cvmix_background_diffusion_passive');
+add_default($nl, 'config_cvmix_background_diffusion_passive_enable');
add_default($nl, 'config_cvmix_background_viscosity');
add_default($nl, 'config_cvmix_BryanLewis_bl1');
add_default($nl, 'config_cvmix_BryanLewis_bl2');
diff --git a/components/mpas-ocean/bld/namelist_files/namelist_defaults_mpaso.xml b/components/mpas-ocean/bld/namelist_files/namelist_defaults_mpaso.xml
index 1a72035aba3b..248654ef10f5 100644
--- a/components/mpas-ocean/bld/namelist_files/namelist_defaults_mpaso.xml
+++ b/components/mpas-ocean/bld/namelist_files/namelist_defaults_mpaso.xml
@@ -275,6 +275,8 @@
1.0
'constant'
0.0
+0.0
+.false.
1.0e-4
8.0e-5
1.05E-4
diff --git a/components/mpas-ocean/bld/namelist_files/namelist_definition_mpaso.xml b/components/mpas-ocean/bld/namelist_files/namelist_definition_mpaso.xml
index 4be3335c7aab..cd8535a41587 100644
--- a/components/mpas-ocean/bld/namelist_files/namelist_definition_mpaso.xml
+++ b/components/mpas-ocean/bld/namelist_files/namelist_definition_mpaso.xml
@@ -747,6 +747,22 @@ Valid values: Any positive real value.
Default: Defined in namelist_defaults.xml
+
+Background vertical diffusion applied to passive tracer quantities
+
+Valid values: Any positive real value.
+Default: Defined in namelist_defaults.xml
+
+
+
+flag to enable using a different background vertical diffusion for passive tracers
+
+Valid values: .true. or .false.
+Default: Defined in namelist_defaults.xml
+
+
Background vertical viscosity applied to horizontal velocity
diff --git a/components/mpas-ocean/src/Registry.xml b/components/mpas-ocean/src/Registry.xml
index f4481a617dfe..475a2751def9 100644
--- a/components/mpas-ocean/src/Registry.xml
+++ b/components/mpas-ocean/src/Registry.xml
@@ -480,6 +480,14 @@
description="Background vertical diffusion applied to tracer quantities"
possible_values="Any positive real value."
/>
+
+
+