diff --git a/components/mpas-ocean/cime_config/buildnml b/components/mpas-ocean/cime_config/buildnml
index a363c27883a3..b667f6880901 100755
--- a/components/mpas-ocean/cime_config/buildnml
+++ b/components/mpas-ocean/cime_config/buildnml
@@ -1006,7 +1006,7 @@ def buildnml(case, caseroot, compname):
             lines.append('        filename_interval="00-01-00_00:00:00"')
             lines.append('        reference_time="01-01-01_00:00:00"')
             lines.append('        output_interval="00-01-00_00:00:00"')
-            lines.append('        clobber_mode="append"')
+            lines.append('        clobber_mode="truncate"')
             lines.append('        packages="conservationCheckAMPKG">')
             lines.append('')
             lines.append('<var name="xtime"/>')