diff --git a/pysurfex/cli.py b/pysurfex/cli.py
index c3fffae..7740e01 100644
--- a/pysurfex/cli.py
+++ b/pysurfex/cli.py
@@ -167,6 +167,13 @@ def run_first_guess_for_oi(**kwargs):
                 fileformat = kwargs["sd_format"]
             if "sd_converter" in kwargs and kwargs["sd_converter"] is not None:
                 converter = kwargs["sd_converter"]
+        elif var == "sea_ice_thickness":
+            if "icetk_file" in kwargs and kwargs["icetk_file"] is not None:
+                inputfile = kwargs["icetk_file"]
+            if "icetk_format" in kwargs and kwargs["icetk_format"] is not None:
+                fileformat = kwargs["icetk_format"]
+            if "icetk_converter" in kwargs and kwargs["icetk_converter"] is not None:
+                converter = kwargs["icetk_converter"]
         elif var == "cloud_base":
             if "cb_file" in kwargs and kwargs["cb_file"] is not None:
                 inputfile = kwargs["cb_file"]
diff --git a/pysurfex/cmd_parsing.py b/pysurfex/cmd_parsing.py
index dc1d09e..0dcd135 100644
--- a/pysurfex/cmd_parsing.py
+++ b/pysurfex/cmd_parsing.py
@@ -618,6 +618,26 @@ def parse_args_first_guess_for_oi(argv):
         choices=["none", "sweclim", "swe2sd", "sdp"],
     )
 
+    parser.add_argument(
+        "-icetk_file", type=str, default=None, help="Ice thickness file", nargs="?"
+    )
+    parser.add_argument(
+        "-icetk_format",
+        type=str,
+        default=None,
+        help="Ice thickness file format",
+        nargs="?",
+        choices=["fa"],
+    )
+    parser.add_argument(
+        "--icetk_converter",
+        type=str,
+        default="none",
+        help="",
+        nargs="?",
+        choices=["none"],
+    )
+
     parser.add_argument(
         "-cb_file", type=str, default=None, help="Cloud base file", nargs="?"
     )
@@ -721,6 +741,7 @@ def parse_args_first_guess_for_oi(argv):
             "air_temperature_2m",
             "relative_humidity_2m",
             "surface_snow_thickness",
+            "sea_ice_thickness",
             "cloud_base",
             "surface_soil_moisture",
         ],
diff --git a/pysurfex/netcdf.py b/pysurfex/netcdf.py
index 10c8da1..c5fb157 100644
--- a/pysurfex/netcdf.py
+++ b/pysurfex/netcdf.py
@@ -643,6 +643,7 @@ def create_netcdf_first_guess_template(
         "relative_humidity_2m": "relative_humidity",
         "altitude": "altitude",
         "surface_snow_thickness": "surface_snow_thickness",
+        "sea_ice_thickness": "sea_ice_thickness",
         "surface_soil_moisture": "surface_soil_moisture",
         "cloud_base": "cloud_base",
         "land_area_fraction": "land_area_fraction",
@@ -652,6 +653,7 @@ def create_netcdf_first_guess_template(
         "relative_humidity_2m": "Screen level relative humidity (RH2M)",
         "altitude": "Altitude",
         "surface_snow_thickness": "Surface snow thickness",
+        "sea_ice_thickness": "Sea ice thickness",
         "surface_soil_moisture": "Surface soil moisture",
         "cloud_base": "Cloud base",
         "land_area_fraction": "Land Area Fraction",
@@ -661,6 +663,7 @@ def create_netcdf_first_guess_template(
         "relative_humidity_2m": "1",
         "altitude": "m",
         "surface_snow_thickness": "m",
+        "sea_ice_thickness": "m",
         "surface_soil_moisture": "m3/m3",
         "cloud_base": "m",
         "land_area_fraction": "1",
@@ -670,6 +673,7 @@ def create_netcdf_first_guess_template(
         "relative_humidity_2m": "9.96921e+36",
         "altitude": "9.96921e+36",
         "surface_snow_thickness": "9.96921e+36",
+        "sea_ice_thickness": "9.96921e+36",
         "surface_soil_moisture": "9.96921e+36",
         "cloud_base": "9.96921e+36",
         "land_area_fraction": "9.96921e+36",