Sea ice in the Antarctic winter is at historic lows.

Satellite data reveals that the sea ice surrounding Antarctica is well below any previously seen winter level, setting a troubling new standard for an area that previously appeared to be impervious to global warming.

Walter Meier, who monitors sea-ice for the National Snow and Ice Data Centre, said it is "so far outside anything we've seen, it's almost mind-blowing."

The vast area of ice that makes up Antarctica controls the planet's temperature by reflecting the Sun's energy back into the atmosphere.

Polar specialists have feared that an unstable Antarctica might have far-reaching effects.