Coldest of the cold
Earth’s most frigid region, under certain circumstances, is even colder than Mars
For several years, scientists have known that the coldest weather on Earth was tucked in the valleys near the top of Antarctica’s ice sheet. Weather satellites had detected temperatures there that could tumble as low as -93 C. But a new analysis of satellite data finds the planet’s coldest spot is even more frigid, and can see temperatures plunge as low as nearly minus 100 degrees at night during Antarctic winter.
The authors of the new study, published in Geophysical Research Letters, found “approximately 100” sites that posted low temperatures of around -144 during the winters of 2004 to 2016. Most frequently, these temperatures, colder than the average temperature on Mars (around -76), were observed in dips and hollows near the top of the East Antarctic Ice Sheet. They occurred at elevations of about 3,800 metres to 4,000 metres, mostly during July and August.
Prior to analysis of satellite data, the coldest temperature measured on Earth had been -89, recorded on the East Antarctic Plateau at Russia’s Vostok Station in July 1983. The satellite data analysis published in 2013 analyzed 32 years’ worth of data to find that colder temperatures were present, closer to -135. This latest study recalibrated satellite data using more up-to-date weather station data and concluded that the coldest temperatures were 5 degrees lower than that.
The locations where the -144 air was analyzed shared similar characteristics.
“They occurred in small hollows 2 to 3 metres deep in the surface of the ice, on the southern side of high ridges on the plateau,” the study’s news release explained. Remarkably, the lowest temperatures observed at all of these hollows on the ice sheet was right around -144, even though some of them were spaced tens of kilometres apart. In other words, the
scientists found that -144 seemed to represent the floor or the theoretical minimum for how cold it can get.
Such a frigid temperature reading is possible only under very specific weather conditions, the study found.
The sky must be clear and winds calm to allow for any residual heat to radiate away from the Earth’s surface back into space. It must also be as dry as possible, as water vapour, which is a greenhouse gas, can retain heat in the atmosphere.
If the air was extremely dry for a long period of time, it’s possible the temperature could go lower than -144, but not by much. “There’s a limit to how long the conditions persist to allow it to cool to these ultra-low temperatures, and a limit to how much heat you can actually get through the atmosphere, because water vapour has to be almost nonexistent in order to emit heat from the surface at these temperatures,” said Ted Scambos, a scientist at the National Snow and Ice Data Center and study lead author.
Will climate warming due to increasing concentrations of greenhouse gases in the atmosphere from human activity raise the floor for this minimum temperature? Scambos says it’s possible. “Going forward in time, I think we could see that the lower limit might slowly start to rise, as we put more carbon dioxide in the air, and water vapour in the stratosphere starts to increase,” he said.