This monitoring station disappeared toward the end, or shortly after, a major Russian naval exercise involving almost all of their northern fleet.
The US has moved an aircraft carrier, the Harry S Truman, near the coast of Norway, perhaps to observe Russian activity.
The Russians have two diesel-electric boats, both Kilo class, in the Baltic. Apparently, one of them has been out of commission for a while. The rumour is that they're significantly upgrading their Baltic submarine fleet.
While no passive sonar function has been disclosed for this station, it is fairly new, expensive and high-tech. It was deployed recently as an upgrade to the German data collection system in Kiel Bay.
Perhaps the Russians wished to transfer nuclear submarines to the Baltic to upgrade their fleet, and this station was seen as a concern.