Definition of "icebound"

KGB had always been on the lookout for hard facts, but then reported those facts to people besotted with a dream, who then bent the truth in the service of that dream. When the truth had finally broken through, the dream had suddenly evaporated like a cloud of steam in a high wind, and reality had poured in like the flood following the breakup of an icebound river in springtime.

2001, Tom Clancy, The Bear and the Dragon