diff --git a/cdds/cdds/common/plugins/cmip7/cmip7_grid.py b/cdds/cdds/common/plugins/cmip7/cmip7_grid.py
index eb2f638e9..202f46ca1 100644
--- a/cdds/cdds/common/plugins/cmip7/cmip7_grid.py
+++ b/cdds/cdds/common/plugins/cmip7/cmip7_grid.py
@@ -40,7 +40,7 @@ def from_name(cls, name: str) -> 'GridLabel':
     NATIVE = 'native', 'g100', False
     NATIVE_ZONAL = 'native-zonal', 'g100z', False
     REGRIDDED = 'regridded', 'g100', False
-    GLOBAL_MEAN = 'global-mean', 'g100m', False
+    GLOBAL_MEAN = 'global-mean', 'g100', False
     UGRID = 'ugrid', 'g100', True
     VGRID = 'vgrid', 'g100', True
     UVGRID = 'uvgrid', 'g100', True
diff --git a/mip_convert/mip_convert/plugins/base/data/processors.py b/mip_convert/mip_convert/plugins/base/data/processors.py
index 2de3b2fdc..3a47462d0 100644
--- a/mip_convert/mip_convert/plugins/base/data/processors.py
+++ b/mip_convert/mip_convert/plugins/base/data/processors.py
@@ -1172,6 +1172,11 @@ def calc_zostoga(thetao, thkcello, areacello, zfullo_0, so_0, rho_0_mean, deptho
         Intercomparison Project. Geoscientific Model Development,
         9(9), pp.3231-3296.
     """
+    # Ensure the vertical coordinate is named consistently before processing
+    for cube in [thetao, thkcello]:
+        if not cube.coords('depth'):
+            _z_axis(cube).rename('depth')
+
     rho_mean = iris.cube.CubeList()
 
     so_0 = iris.util.squeeze(so_0)
diff --git a/mip_convert/mip_convert/save/cmor/cmor_wrapper.py b/mip_convert/mip_convert/save/cmor/cmor_wrapper.py
index 745edfdeb..56c5a6463 100644
--- a/mip_convert/mip_convert/save/cmor/cmor_wrapper.py
+++ b/mip_convert/mip_convert/save/cmor/cmor_wrapper.py
@@ -113,5 +113,5 @@ def zfactor(self, *args, **kwargs):
         cmor.zfactor(*args, **kwargs)
 
     def set_frequency(self, frequency, **kwargs):
-        self._debug_on_args('frequency', frequency, kwargs)
+        self._debug_on_args('frequency', [frequency], kwargs)
         cmor.cmor.set_cur_dataset_attribute('frequency', frequency)
diff --git a/mip_convert/mip_convert/tests/test_functional/test_functional_cmip7/test_cmip7_mon_zostoga_tavg_u_hm_sea.py b/mip_convert/mip_convert/tests/test_functional/test_functional_cmip7/test_cmip7_mon_zostoga_tavg_u_hm_sea.py
new file mode 100644
index 000000000..3a1bfbfab
--- /dev/null
+++ b/mip_convert/mip_convert/tests/test_functional/test_functional_cmip7/test_cmip7_mon_zostoga_tavg_u_hm_sea.py
@@ -0,0 +1,64 @@
+# (C) British Crown Copyright 2026, Met Office.
+# Please see LICENSE.md for license details.
+import os
+
+import pytest
+
+from mip_convert.tests.test_functional.test_command_line import AbstractFunctionalTests
+from mip_convert.tests.test_functional.utils.configurations import Cmip7TestData, SpecificInfo
+from mip_convert.tests.test_functional.utils.directories import (ROOT_ANCIL_TESTING_DIR, get_cmor_log, get_output_dir,
+                                                                 MODEL_OUTPUT_DIR,
+                                                                 ROOT_OUTPUT_CASES_DIR)
+
+
+class TestCmip7_zostoga_tavg_u_hm_sea(AbstractFunctionalTests):
+
+    def get_test_data(self):
+        test_location = os.path.join(ROOT_OUTPUT_CASES_DIR, 'test_CMIP7_ocean_zostoga_tavg-u-hm-sea')
+        return Cmip7TestData(
+            mip_table='ocean',
+            variables=['zostoga_tavg-u-hm-sea'],
+            specific_info=SpecificInfo(
+                common={
+                    'test_location': test_location
+                },
+                cmor_setup={
+                    'cmor_log_file': get_cmor_log(test_location),
+                },
+                cmor_dataset={
+                    'output_dir': get_output_dir(test_location),
+                    'model_id': 'UKCM2-0-LL',
+                    'parent_model_id': 'UKCM2-0-LL',
+                    'variant_label': 'r2i1p1f1',
+                    'calendar': 'standard',
+                    'branch_date_in_child': "1850-01-01T00:00:00",
+                    'branch_date_in_parent': "1850-01-01T00:00:00",
+                },
+                request={
+                    'ancil_files': ' '.join([
+                        os.path.join(ROOT_ANCIL_TESTING_DIR, 'UKCM2-0-LL', 'ocean_zostoga.nc'),
+                        os.path.join(ROOT_ANCIL_TESTING_DIR, 'UKCM2-0-LL', 'ocean_constants.nc')
+                    ]),
+                    'model_output_dir': MODEL_OUTPUT_DIR,
+                    'run_bounds': '1900-01-01T00:00:00 1900-02-01T00:00:00',
+                    'suite_id': 'u-dv623',
+                    'mip_convert_plugin': 'UKCM2'
+                },
+                streams={
+                    'onm': {'CMIP7_ocean@mon': 'zostoga_tavg-u-hm-sea'}
+                },
+                halo_removal={
+                    'onm': '1:-1,1:-1'
+                },
+                other={
+                    'reference_version': 'v1',
+                    'filenames': ['zostoga_tavg-u-hm-sea_mon_glb_g100_UKCM2-0-LL_1pctCO2_r2i1p1f1_190001-190001.nc'],
+                    'ignore_history': True,
+                }
+            )
+        )
+
+    @pytest.mark.slow
+    def test_cmip7_mon_zostoga(self):
+        self.maxDiff = True
+        self.check_convert(plugin_id="CMIP7")
diff --git a/mip_convert/mip_convert/tests/test_functional/utils/directories.py b/mip_convert/mip_convert/tests/test_functional/utils/directories.py
index 50abbd82d..b041b9d92 100644
--- a/mip_convert/mip_convert/tests/test_functional/utils/directories.py
+++ b/mip_convert/mip_convert/tests/test_functional/utils/directories.py
@@ -12,6 +12,7 @@
 TEST_DIR_NAME_TEMPLATE = 'test_{project}_{mip_table}_{variable}'
 
 ROOT_ANCIL_DIR = os.path.join(CDDS_ETC, 'ancil')
+ROOT_ANCIL_TESTING_DIR = os.path.join(CDDS_ETC, 'ancil_testing')
 
 ROOT_MIP_TABLES_DIR = os.path.join(CDDS_ETC, 'mip_tables')
 CORDEX_MIP_TABLE_DIR = '{}/CORDEX/cordex-cmip6-cmor-tables/Tables'.format(ROOT_MIP_TABLES_DIR)