No-one knows if the trend will continue. If it does, the Arctic Ocean could be completely free of summer ice towards the end of this century. That could devastate the wildlife that relies on it for hunting, breeding, and protection from shipping. But for now, though, some species are positively booming. The polar bear population on Alaska's coast has doubled since the '70s, thanks largely to a hunting ban.
Researchers say they have never seen such big and healthy animals.
That may be because at the other end of the food chain, plankton are thriving in warmer waters. At the edge of the solid ice, the spring thaw is beginning and a whale count is under way. Research teams work round the clock monitoring the bowhead whales, which surface in open areas to breathe. Retreating pack ice may also be helping them. A team of researchers has also been monitoring the local polar bears from a helicopter.