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Tiny valleys near the top of the Antarctic ice sheet reach temperatures near -100 degrees Celsius, according to a new study published this week in the AGU journal Geophysical Research Letters. The discovery could change scientists' understanding of how low temperatures can reach the Earth's surface, and how that happens, according to the researchers.
After examining data from several Earth observation satellites, scientists reported temperatures of -93 degrees Celsius (-135 degrees Fahrenheit) at several locations on the East Antarctic Plateau. , a high snowy plateau in central Antarctic that encompasses the South Pole. This preliminary study has been revised with new data showing that the coldest sites actually reach -98 degrees Celsius (-144 degrees Fahrenheit). Temperatures are observed during the southern polar night, especially in July and August.
When the researchers announced that they had found the coldest temperatures on Earth five years ago, they determined that a clear sky and persistent soak it down. But the new study adds a twist to the story: not only is clear skies needed, but the air must also be extremely dry, as water vapor blocks heat loss from the surface snow.
Temperatures in small depressions or shallow troughs in the Antarctic Ice Sheet where cold, dense, and descending air is present above the surface and may remain for several days. This allows the surface and air above to cool further, until the clear, calm, dry conditions degrade and the air mixes with the air. warmer air higher in the atmosphere
. "This allows the heat of the snow surface to radiate more easily into space," says Ted Scambos, principal investigator at the National Snow and Ice Data Center at the University of Colorado Boulder. and lead author of the study.
The record -98 degrees Celsius is about as cold as it is possible to reach the Earth's surface, according to the researchers. In order for the temperature to fall so low, clear skies and dry air must persist for several days. Scambos said the temperatures could drop a bit if the conditions lasted several weeks, but this is very unlikely,
Finding the coldest place
The high altitude of the Eastern Antarctic plateau and its proximity with The South Pole gives it the coldest climate of all regions of the planet. The lowest air temperature ever measured by a weather station, -89 degrees Celsius (-128 degrees Fahrenheit), was recorded at the Russian Vostok station in July 1983.
But weather stations do not can measure temperatures everywhere. Thus, in 2013, Scambos and his colleagues decided to analyze data from several Earth observation satellites to see if they could find temperatures even lower than those recorded at Vostok
. They used data from the MODIS instrument aboard NASA's Terra and Aqua satellites, as well as data from NOAA polar operational meteorological satellites
Researchers observed snow surface temperatures consistently below -90 degrees. Celsius (-130 degrees Fahrenheit) almost every winter in a large area of the plateau, more than 3500 meters (11 000 feet) above sea level. Within this vast region, they discovered that dozens of sites had much colder temperatures. Nearly 100 places reached surface temperatures of -98 degrees Celsius
. The atmosphere of this region can sometimes contain less than 0.2 mm of total precipitable water above the surface. But even when it is dry and cold, the air traps some of the heat and returns it to the surface. This means that cooling speeds are very slow as surface temperatures approach the recorded values.
Conditions do not persist long enough – it can take weeks – for temperatures to drop below observed records. However, the temperature measured by the satellites is the temperature of the surface of the snow, and not the air above. The study also estimated the air temperature using nearby automatic weather stations and satellite data.
Interestingly, even though the coldest sites extended over hundreds of kilometers, the lowest temperatures were almost identical. This made them wonder: Is there a limit to the cold on the set?
How cold is it?
Using the difference between the satellite measurements of the lowest snow temperatures at Vostok and three automated stations, and the air temperatures at the same place and at the same time, the researchers deduced that the temperatures of the The air at the coldest places (where no station exists) is probably around -94 degrees Celsius, or about -137 degrees Fahrenheit. ] The research team has also developed a set of instruments designed to survive and operate in the coldest places in the winter and measure the temperatures of the snow and air. They plan to deploy the instruments in the next year or two, during the Antarctic summer when temperatures are relatively mild of -30 degrees Celsius (-22 degrees Fahrenheit).
Research Document
Related Links
University of Colorado at Boulder
Beyond the Ice Age
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The Spongy Interior of the Earth quickly gives birth to Antarctica
Paris (ESA) June 25, 2018
Parts of the Earth's crust grow very slowly due to postglacial rebound, but using GPS, researchers found that Western Antarctica is growing faster than almost everywhere else in the world. In addition, ESA's gravity mission GOCE helped them understand that the coat below is exceptionally fluid.
About 20,000 years ago, vast expanses of the Earth's surface were covered with thick ice. In some places, the ice was 3 km thick – just like Central Antarctica and Greenland today.
Earth's hard r … read more
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