Earthly cold record
For the first time, researchers are measuring minus 98 degrees in sinks on the Antarctic PlateauRead out
On Earth, it can be colder than previously thought: In the Antarctic, researchers have measured using satellites temperatures of minus 98 degrees - a new cold record. These record highs occur in snowcaps of the Antarctic Plateau when the sky is clear and the air is very dry in the polar winter. Scientists suspect that these are the lowest temperatures that can ever occur on our planet.
How cold can it be on our planet? Researchers have been asking themselves this question for some time. It is known that the interior of the Antarctic offers the right conditions to achieve cold records. Only here, far away from the sea and in some places more than 3, 000 meters in height, the air in the polar winter cools down far enough. The Russian polar station Wostok lying on this plateau was therefore for a long time the record holder: There was 1983 a temperature of minus 89, 2 degrees measured.
Cold zone at the Antarctic Ice Sheath
In 2013, however, researchers discovered an even colder place: satellite data revealed that it could be down to minus 93.2 degrees Celsius in a series of dips between the two peaks, Dome Argus and Dome Fuji - a new record. This region on the ice shed of the Antarctic plateau is sometimes more than 3, 500 meters high.
The surprising thing is that this cold zone is almost a thousand kilometers long and in it there are amazingly many places with cold extremes. But why? To find out, Ted Scambos from the University of Colorado at Boulder and his team have once again analyzed satellite data on the thermal emissions of this area from 2004 to 2016. These high-resolution data compared them with weather data from on-site measurements.No region of the world is as cold as the more than 3, 000 meter high Antarctic polar plateau © Ted Scambos / NSIDC / CU Boulder
Minus 98.6 degrees Celsius - cold record
The result: The temperatures in this cold zone sink even lower in winter than previously thought. At around 100 sites, researchers measured values of less than minus 98 degrees an on the snow surface, several dozen times during the study period. The absolute cold record was reached on July 23, 2004: On that day, the satellites registered in one of the sinks even minus 98.6 degrees, as Scambos and his colleagues report. display
"This temperature seems to be about as deep as it is possible at all, " say the researchers. They suggest that these values are close to the absolute minimum for our planet. They therefore consider it unlikely that further, significantly lower Czech records will be measured in the future not least because of climate change.
Clear skies and extremely dry air
But how does the record cold come about? The astonishing uniformity of the values provided a first indication: Although the Antarctic cooling zone is 900 kilometers long and around 100 kilometers wide, the minimum temperatures in the snow banks hardly vary. "The narrow range of minimum temperatures in such a large area suggests that there is a physical factor that limits temperatures, " the researchers speculate.The cold, dry atmosphere allows the air to emit a lot of heat over the snowpack. In sinks, it collects and continues to cool. NASA / GSFC
Further analysis of terrain and weather data revealed that extreme colds always occur when the sky is clear for several days and the air is extremely dry. And this is exactly where the researchers see the reason for the cooling zone: water vapor in the air absorbs heat and can therefore act like an electric blanket. But otherwise dry air: "It makes it easier for the snow surface to radiate its heat to space, " explains Scambos. "And there are periods of incredibly dry air in this area."
Schneesenken as a cold trap
As the researchers explain, the dry air and clear skies ensure that the snowpack in this cooling zone can emit a lot of heat. The cold air then flows down the slopes of the ridge and collects in the snowcaps. There it continues to cool, reaching record levels of 98 degrees and just below.
Could there be even lower temperatures in these valleys than previously measured? In theory, this would be possible if the clear, dry conditions last for several weeks, as Scambos explains. That is very unlikely. "There is a limit to how long these conditions will last and also an upper limit for the heat that can radiate through the atmosphere, " says the researcher. (Geophysical Research Letters, 2018; doi: 10.1029 / 2018GL078133)
(American Geophysical Union, University of Colorado, 27.06.2018 - NPO)