diff --git a/src/core_ocean/Registry.xml b/src/core_ocean/Registry.xml
index b182b7ac8a..1dc15a983a 100644
--- a/src/core_ocean/Registry.xml
+++ b/src/core_ocean/Registry.xml
@@ -943,6 +943,10 @@
 					description="Dimensionless bottom drag coefficient, $c_{drag}$."
 					possible_values="any positive real, typically 1.0e-3"
 		/>
+		<nml_option name="config_use_implicit_bottom_roughness" type="logical" default_value=".false." units="unitless"
+					description="If true, depends on bottom roughness z0"
+					possible_values=".true. or .false."
+		/>
 		<nml_option name="config_use_implicit_bottom_drag_variable" type="logical" default_value=".false." units="unitless"
 					description="If true, spatially-variable implicit bottom drag is used on the momentum equation."
 					possible_values=".true. or .false."
diff --git a/src/core_ocean/shared/mpas_ocn_vel_tidal_potential.F b/src/core_ocean/shared/mpas_ocn_vel_tidal_potential.F
index 57362b26e8..6d1c862e9a 100644
--- a/src/core_ocean/shared/mpas_ocn_vel_tidal_potential.F
+++ b/src/core_ocean/shared/mpas_ocn_vel_tidal_potential.F
@@ -218,7 +218,7 @@ subroutine ocn_compute_tidal_potential_forcing(err)!{{{
          conType        ! id for constituent type
 
       real (kind=RKIND) :: &
-         lon,&
+         lat, lon,&
          tArg,&
          ramp,&
          t, &
@@ -250,6 +250,11 @@ subroutine ocn_compute_tidal_potential_forcing(err)!{{{
          conType = tidalConstituentType(jCon)
          do iCell = 1, nCellsAll
            lon = lonCell(iCell)
+           lat = latCell(iCell)
+           latitudeFunction(iCell,1) = 3.0_RKIND*sin(lat)**2 -1.0_RKIND
+           latitudeFunction(iCell,2) = sin(2.0_RKIND*lat)
+           latitudeFunction(iCell,3) = cos(lat)**2
+
            tidalPotEta(iCell) = tidalPotEta(iCell) + &
                          ramp * tidalConstituentAmplitude(jCon) &
                               * tidalConstituentNodalAmplitude(jCon) &
diff --git a/src/core_ocean/shared/mpas_ocn_vmix.F b/src/core_ocean/shared/mpas_ocn_vmix.F
index 375d97ed52..d64ce6ba0f 100644
--- a/src/core_ocean/shared/mpas_ocn_vmix.F
+++ b/src/core_ocean/shared/mpas_ocn_vmix.F
@@ -821,7 +821,11 @@ subroutine ocn_vel_vmix_tend_implicit_spatially_variable_mannings(meshPool, forc
          end do
 
          ! average cell-based implicit bottom drag to edges and convert Mannings n to Cd
-         if (config_use_vegetation_drag .AND. config_use_vegetation_manning_equation) then
+         if (config_use_implicit_bottom_roughness) then
+           implicitCd = max(0.0025_RKIND, &
+                        min(0.1_RKIND, &
+                          0.16_RKIND/log(250.0_RKIND*(bottomDepth(cell1)+bottomDepth(cell2)))**2 ))
+         elseif (config_use_vegetation_drag .AND. config_use_vegetation_manning_equation) then
            implicitCd = gravity*(0.5_RKIND*(vegetationManning(cell1) + vegetationManning(cell2)))**2.0 * &
             (0.5_RKIND * (ssh(cell1) + ssh(cell2) + bottomDepth(cell1) + bottomDepth(cell2)))**(-1.0_RKIND/3.0_RKIND)
          else
@@ -1137,7 +1141,8 @@ subroutine ocn_vmix_implicit(dt, meshPool, statePool, forcingPool, scratchPool,
       if (config_use_implicit_bottom_drag_variable) then
         call ocn_vel_vmix_tend_implicit_spatially_variable(meshPool, bottomDrag, dt, kineticEnergyCell, &
           vertViscTopOfEdge, layerThickness, layerThickEdge, normalVelocity, err)
-      else if (config_use_implicit_bottom_drag_variable_mannings) then
+      else if (config_use_implicit_bottom_drag_variable_mannings.or. &
+               config_use_implicit_bottom_roughness) then
         ! update bottomDrag via Cd=g*n^2*h^(-1/3)
         call ocn_vel_vmix_tend_implicit_spatially_variable_mannings(meshPool, forcingPool, bottomDrag, &
           dt, kineticEnergyCell, &