From c773b781499291b571001bbee496f1ae854d3614 Mon Sep 17 00:00:00 2001
From: Carolyn Begeman <cbegeman@lanl.gov>
Date: Wed, 25 Oct 2023 16:45:19 -0500
Subject: [PATCH] Add linear tide forcing option

---
 components/mpas-ocean/src/Registry.xml             | 14 +++++++++++++-
 .../mpas-ocean/src/shared/mpas_ocn_tidal_forcing.F |  4 ++++
 2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/components/mpas-ocean/src/Registry.xml b/components/mpas-ocean/src/Registry.xml
index 7008093f0826..0cf8b0b2ae60 100644
--- a/components/mpas-ocean/src/Registry.xml
+++ b/components/mpas-ocean/src/Registry.xml
@@ -797,7 +797,7 @@
 		/>
 		<nml_option name="config_tidal_forcing_model" type="character" default_value="off"
 					description="Selects the mode in which tidal forcing is computed."
-					possible_values="'off','monochromatic'"
+					possible_values="'off','monochromatic','linear'"
 		/>
 		<nml_option name="config_tidal_forcing_monochromatic_amp" type="real" default_value="2.0" units="m"
 					description="Value of amplitude of monochromatic tide."
@@ -815,6 +815,18 @@
 					description="Value of baseline monochromatic tide, e.g., sea level rise."
 					possible_values="Any positive real number."
 		/>
+		<nml_option name="config_tidal_forcing_linear_baseline" type="real" default_value="0.0" units="days"
+					description="Value of baseline linear tide, e.g., sea level rise."
+					possible_values="Any positive real number."
+		/>
+		<nml_option name="config_tidal_forcing_linear_min" type="real" default_value="-1.0" units="days"
+					description="Value of minimum tide."
+					possible_values="Any real number."
+		/>
+		<nml_option name="config_tidal_forcing_linear_rate" type="real" default_value="-8.0" units="days"
+					description="Value of tide rate of change in m per day."
+					possible_values="Any real number."
+		/>
 	</nml_record>
 	<nml_record name="self_attraction_loading" mode="init;forward">
 		<nml_option name="config_use_self_attraction_loading" type="logical" default_value=".false."
diff --git a/components/mpas-ocean/src/shared/mpas_ocn_tidal_forcing.F b/components/mpas-ocean/src/shared/mpas_ocn_tidal_forcing.F
index 98a6f99e77bd..35df6959441e 100644
--- a/components/mpas-ocean/src/shared/mpas_ocn_tidal_forcing.F
+++ b/components/mpas-ocean/src/shared/mpas_ocn_tidal_forcing.F
@@ -245,6 +245,10 @@ subroutine ocn_tidal_forcing_build_array(domain, meshPool, forcingPool, statePoo
             SIN(2.0_RKIND*pii/config_tidal_forcing_monochromatic_period * daysSinceStartOfSim - &
             pii*config_tidal_forcing_monochromatic_phaseLag/180.0_RKIND) - &
             config_tidal_forcing_monochromatic_baseline
+        elseif (trim(config_tidal_forcing_model) == 'linear') then
+           tidalHeight = max(config_tidal_forcing_linear_min, &
+                             config_tidal_forcing_linear_baseline + &
+                             config_tidal_forcing_linear_rate * daysSinceStartOfSim)
         !else if (trim(config_tidal_forcing_type) == 'data') then
         !  ! data option
         !  ! pass