Scientists have confirmed Antarctic sea ice reached its third-lowest winter maximum in the satellite record, peaking at 17.59 million square kilometres on September 14.
Coverage fell about one million square kilometres short of the long-term average maximum. All four of the lowest winter peaks have occurred in the past four years. Satellite monitoring began in 1979.
Dr Walt Meier, a senior scientist at the National Snow and Ice Data Centre at the University of Colorado, said researchers delayed declaring the peak because ice coverage can fluctuate sharply.
Its subsequent decline convinced him that winter growth had ended. Dr Ariaan Purich, a Southern Ocean expert at Monash University in Melbourne, linked the repeated lows to a warming climate.
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“This is not a future problem. It’s a now problem.” Purich explained that reduced ice cover allows the Southern Ocean to absorb more solar energy as daylight returns after the polar winter.
Wind patterns have also affected ice growth. Purich identified El Niño-related wind changes as a likely contributor to losses in the Amundsen Sea in early August.
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However, Dr Phil Reid, who monitors Antarctic conditions at Australia’s Bureau of Meteorology, warned that similarly low coverage could have occurred without El Niño. Warmer water limits how much ice can form.
Floating sea ice does not directly raise sea levels when it melts. Its retreat can, however, expose ice shelves to ocean extremes and weaken structures that slow glaciers’ movement towards the sea.
Sea ice provides habitat for algae and krill. Emperor penguins also depend on stable ice to breed and raise their young.
