The area covered by sea ice in Antarctica has fallen to its lowest level, according to records that began in the late 1970s.

The record, set on February 25, is the second sharp drop in ice coverage in just five years, Chinese researchers from Sun Yat-sen University in Guangzhou and the Laboratory of Southern Marine Science in Zhuhai report in the journal Advances in Atmospheric Sciences.

They have been investigating ocean currents and weather phenomena behind the melting, but are still faced with mysteries.

While ice in the Arctic is rapidly decreasing due to global warming, the ice surface in the Antarctic has tended to increase by about one per cent every decade since the 1970s.

After an unusual decline recorded in 2017, it happened again this year at the end of the summer in the southern hemisphere.

For the first time, the extent of Antarctic ice fell to less than two million square kilometres – about 30 per cent less than the average for the years 1981 to 2010.

The climate change service of the EU Copernicus program has also reported the daily measured extent of Antarctic sea ice this February had reached its lowest level since records began in 1979.