Australian Broadcasting Corporation: A year ago US scientists caused alarm when they predicted the Arctic Ocean could be free of summer ice by 2030, but now researchers say those estimates were too conservative. A US-based team has told a conference in California that the northern polar waters could be ice-free in summer by 2013. This year’s northern summer melt in the Arctic reduced the ice cover to just over 4 million square kilometres, the smallest ever amount recorded in modern times. It is this kind of …