You can’t copy Time Machine backups around as they are not only actual files but also special timestamped links as well (easy explained), so if you try the Mac OS will give you errors and prevent you from doing that. If you should be able to do it in some strange way the backup will probably be of no use anymore.
With this fast Tunderbolt drive you should start a new TM backup as it will go very fast.
If your OS X is of the later versions you can just add a new drive to backup to and it will use both drives if present or jut one or the other whichever is in use at the time.
