Satellite data has shown that the sea-ice surrounding Antarctica is well below any previous recorded winter level, a worrying new benchmark for a region that once seemed resistant to global warming. An unstable Antarctica could have far-reaching consequences, polar experts warn: its huge ice expanse regulates the planet's temperature, as the white surface reflects the sun's energy back into the atmosphere and also cools the water beneath and near it. Without its ice cooling the planet, Antarctica could transform from Earth's refrigerator to a radiator. The ice that floats on the Antarctic Ocean's surface now measures less than 17 million sq km - that is 1.5 million sq km of sea-ice less than the September average, and well below previous winter record lows. That is an area of missing ice about five times the size of the British Isles. Since the 1990s, the loss of land ice from Antarctica has contributed 7.2mm to sea-level rise: even modest increases in sea levels can result in dangerously high storm surges that could wipe out coastal communities.