You should be able to use the m3tools program m3edhdr to change a time dependent file to a time independent file.
https://www.cmascenter.org/ioapi/documentation/all_versions/html/M3EDHDR.html
The steps would be something like this:
setenv INFILE /path/to/your/file.nc
m3edhdr << EOF
INFILE
4
(hit enter twice)
0
10
EOF
After doing that, TSTEP of your file should be 0 which indicates a time independent file.