This name is a synonym of Juncus balticus subsp. ater (Rydb.) Snogerup.
The record derives from IOPI
(data supplied on 2012-03-23)
which reports it as a synonym (record 314412) with original publication details: Andersons's Fl. Alaska 611 1974.
This name was in version 1 of The Plant List, record kew-314412.