How about, the mixture is already pretty rich because of the ice restricting the air's passage past the butterfly, you introduce hot air, does the ice vanish immediately? nup, the hot air is less dense, the restriction remains( for a short while), therefore the mixture is enrichened further, cough cough sputter, The hot air melts the restrictive ice, air/ fuel ratio gets reasonable and you are laughing. Not laughing as much as I am when people tell me the coughing is chunks of ice going through the carby though.