The Arctic Ocean will be ice-free in the summer within the next 30 years, a study says, which will result in "devastating consequences for the Arctic ecosystem," according to McGill University in Montreal. Sea ice is frozen ocean water that melts each summer, then refreezes each winter. The amount of summer sea ice in the Arctic has been steadily shrinking over the past few decades because of global warming. Since satellite records began in 1979, summer Arctic ice has lost 40% of its area and up to 70% of its volume, the Guardian said.