There's something obviously hilarious about Carl burying the suitcase containing a million dollars out in the snow, and marking it with a windshield scraper. He thinks he's going to come back and get it, and live it up with his winnings, but the eeriness and futile atmosphere of the scene—the tiny scraper marking out the suitcase in the snowy endlessness—indicates to the viewer that no one's coming back for that suitcase. Carl's idiocy is making sure that he can't even hold onto this dumb stroke of good fortune.
We see this scene as the ultimate representation of futility in the film. You just know that, one way or another, that money is lost for good.
P.S. Do you watch the TV show Fargo? On the show, the suitcase is found by a similarly desperate character...and all that money doesn't help him in the long run.