I hope that someone can help me track down a story I read quite a few years ago. All I definitely remember is that there are creatures who live underneath an iceberg and they are attempting to propel it from one pole of the planet to the other in an attempt to take over the planet, but if the ice melts then the creatures die.
Edit (based on first comment): The story was in English, but I can't remember if it was a novel or a short-story. I read it in the 1990s (I am almost certain, but maybe late 1980s - definitely not in 2000s or later) but it could easily be an older story. The ice is prone to melting as it crosses the planet's equator and so speed is of the essence. I think (am not 100% certain) that there are also flying, land, and swimming creatures which are not evil (as the ones under the iceberg are), that some of the creatures under the iceberg are sacrificed (they lose their cover under the iceberg and die) as the iceberg melts but that the objective is only for at least some of them make it across, and that these animals are very (and differently) shaped, perhaps some of the land ones with wheels. That's all I can remember. Thanks again.