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Ice in Antarctica (image from 2020)

Photo: Ueslei Marcelino / REUTERS

The sea extent fluctuates greatly throughout the year, usually reaching its minimum in February and its maximum in September. Now U.S. authorities report: The maximum extent of sea ice in Antarctica is likely to have reached a negative record level this year since records began.

According to satellite images, this year's largest ice cover in terms of area, at 16.96 million square kilometres, was probably reached on 10 September. This is the lowest value for this so-called maximum extent in 45 years, as the US space agency Nasa announced. By way of comparison, the average value for the years 1981 to 2010 is 18.71 million square kilometres.

The extent this year is more than one million square kilometers below the previous record low of 1986, said the U.S. National Snow and Ice Data Center (NSIDC) at the University of Colorado in Boulder. It works with NASA.

The current measurements are preliminary and could still be revised, Nasa and the NSIDC said. This is due to persistent winter conditions, which could further increase the extent of the ice, according to the NSIDC. The final analysis is to be published at the beginning of October.

The role of climate change unclear

Both NSIDC and Nasa do not give a reason for the small extent. According to experts, it is unclear whether this is mainly due to man-made climate change – or rather to natural variability.

The Alfred Wegener Institute recently wrote that some significant deviations from the long-term average had already been observed in the past. Compared to the Arctic, the Antarctic Sea has a wider range of maximum and minimum extent, largely due to geographical differences between the two regions. Nevertheless, the current low extent of Antarctic sea ice is unusual.