How does Axel describe their life after this journey at the very end of the novel?

As a result of his travels, Lidenbrock becomes a great man. He deposits Saknussemm’s document in an archive and tells the story of the expedition to all. He is modest in his glory. The writings, though, are translated into every language and attain considerable fame.

One occurrence that Axel and Lidenbrock parse out is the movement of the compass. They realize that during the storm on the Lidenbrock Sea (as they named the great subterranean body of water) the fireball magnetized the iron on the raft and disoriented their compass; this event is what, apparently, reversed the poles.