FAMILY of polar bears huddle together on a tiny iceberg as their world melts before their eyes - causing them to starve.  The mother and her two six-month-old cubs were marooned 60 miles out to sea in Svalbard, Norway, in the Arctic Circle.  The cubs are seen clambering on to the floating ice sheet, while their mother plans their next move.  The blocks of ice sprawled hundreds of miles into the Greenland Sea.  Rising temperatures caused by global warming has seen the polar bear's natural habitat fall apart.  Photographer Dennis Bromage, 37, from Stockton-on-Tees said:  "It's tragic. The baffled bears just stared into the water as if to say, 'where did all the ice go?' "The family were on the ice when it was one big sheet, but then it just broke up around them and they were left stranded."  Dennis, who was only ten feet away from the bears on a boat, said:  "Their main sources of food are out to sea. If forced ashore, they will starve for the summer because there is just nothing for them to eat. "The ice is breaking up earlier and earlier every year. But the bears will cling on to the ice for as long as they can."