To say "Antarctica is cold" will surprise nobody, but just how cold it can get might. Researchers from the National Snow and Ice Data Center (NSIDC) at the University of Colorado Boulder have now identified the coldest places on the planet, where the mercury plummets to almost -100° C (-148° F) under specific conditions.

The area in question is the East Antarctic Plateau, a huge, empty expanse the size of Australia that starts right near the South Pole. Sitting some 3,500 m (11,500 ft) above sea level, the air over the Plateau is extremely still, dry and thin, and while that makes it a perfect spot for future observatories, it also helps it rank among the chilliest places on Earth.

In 1983, a Russian weather station measured a record-low air temperature of -89° C (-128° F) there, and in 2013 satellite data revealed certain pockets could get as cold as -93° C (-135° F). For the new study, the team behind the latter project set out to check if it gets even colder.

To do so, they analyzed data from NASA's Terra and Aqua satellites, as well as the NOAA's Polar Operational Environmental Satellites, gathered during the Antarctic winters between 2004 and 2016. In this data, the team found that snow surface temperatures below -90° C (-130° F) were a regular winter occurrence across the Plateau, while almost 100 spots bottomed out at -98° C (-144° F).

Interestingly, these locations are spread out over hundreds of kilometers but all have the same lowest temperature. According to the team, all of the cold spots are found in shallow dips in the ice sheet, where in still weather the colder, denser air can drop and sit for days at a time. The longer it's there, the colder the air and the surface snow gets, until the wind picks up again and disturbs it.

"In this area, we see periods of incredibly dry air, and this allows the heat from the snow surface to radiate into space more easily," says Ted Scambos, lead author of the study.

The absolute coldest temperatures were found in those pockets of air that sat still for several days, and the team says that for the mercury to drop much further those conditions would need to remain still for a few weeks at a time. Since that's unlikely, the team says this temperature might just be the coldest it could possibly get anywhere on the Earth's surface.

It's worth keeping in mind that the satellite data is measuring the snow surface temperatures. To measure the air temperature requires a ground-based weather station, but using the data on hand the team estimated that the air above those coldest pockets would be around -94° C (-137° F). To get a more accurate reading, the researchers plan to visit some of the sites in the next few years (during summer, of course) and deploy instruments.

The research was published in the journal Geophysical Review Letters.

Source: NSIDC

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