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IT JUST gets bigger. The extent of the sea ice around Antarctica has hit a record high – for the third year running. Counter-intuitively, global warming is responsible.

Since satellite records began in 1979, the winter maximum sea ice cover around Antarctica has been . This year has long been on track for a new annual record, with 150 daily records already set.

The record was finally , according to data from the US analysed by Australia’s Bureau of Meteorology in Hobart.

More sea ice may seem odd in a warmer world, but new records are expected every few years, says of the Antarctic Climate and Ecosystems Cooperative Research Centre in Hobart. That’s because the southern hemisphere warms more slowly than the north, as it has less landmass, boosting the winds that circle Antarctica and pulling cold air onto the sea ice.

The melting of ice on the Antarctic mainland may also be creating more sea ice, by dumping easily frozen fresh water into the ocean, says of the Australian National University in Canberra.

The extra sea ice is a good thing, as it reflects sunlight and slows global warming. But the sea ice is expected to shrink eventually. “By 2100 we will see dramatic reductions,” says Lieser. “Once it goes belly-up it’s not good for the rest of the world.”

This article appeared in print under the headline “Record Antarctic sea ice”