Gustav became desperate once he came to the realization that he and his friends might not survive. They weren’t only dealing with cold water and ice here, but they were also dealing with temperatures that continued dropping, despite how illogical that may seem. Fire wasn't enough to keep them warm. He unleashed every bit of fire that he could, without having to kill his friends in the process, but they had felt the warmth of the burning fire only for a second, before the temperatures dropped back down to -50°C!
Things were not getting better. The only thing that would save them now, was if they escaped this icy trap, and fled. No matter how great a mage one could be, there were little ways to fight such intensive cold temperatures, and live to tell the tale! They had to act quickly.