Antarctic ice melts to January record low

The amount of sea ice around Antarctica has melted to a record low for January, scientists announced last week.

As of January 1, there was 5.4 million square kilometres of sea ice around the continent, the smallest January area since records began in 1978, according to the National Snow and Ice Data Centre.

Sea ice is frozen ocean water that melts each summer, then refreezes each winter. Antarctic sea ice is typically at its smallest in late February or early March, toward the end of summer in the Southern Hemisphere.

‘‘Antarctic sea ice extent is astonishingly low this year, not just near the Ross Ice Shelf, but around most of the continent,’’ Cecilia Bitz, a polar scientist at the University of Washington, told Grist.

Specifically, the area of sea ice around Antarctica on January 1 was 30,000 square kilometres below the previous record low for that date, set in 2017. It was 1.8 million square kilometres below average – an area roughly twice the size of the state of Texas.

With six to eight weeks remaining in the melt season, the ice centre said it remains to be seen whether the Antarctic sea ice will set its all-time record-low minimum.

Sea ice loss – especially in the Arctic and less so in the Antarctic – is one of the clearest signals of global warming, the National Climate Assessment reported last year.

In addition to human-caused warming of the Earth’s atmosphere and oceans, multiple factors – including the geography of Antarctica, the region’s winds, as well as air and ocean temperatures – affect the ice around Antarctica.

‘‘Although it is too soon for us to isolate what caused the rapid December decline and recent record low extents, it is likely that unusual atmospheric conditions and high sea surface temperatures – important factors in the 2016-2017 record lows – are playing a role,’’ according to a statement from the National Snow and Ice Data Center. – TNS