If it's the cast on and bound off ends that you want to seam you can unpick the cast on end in a manner similar to the one shown here
. You'll just be doing it at the first or second row in order to create live sts. Create live sts on the bound off end by just unraveling the bind off and you're ready to graft the two ends together.
There's a wonderful discussion and instructions for grafting k2p2 rib by Amy on this website (the KnittingHelp site) if you search for "grafting k2p2 rib". Good luck with the cowl.