Photos: At -144 degrees, scientists found the coldest place on Earth

Scientists have discovered the coldest place on Earth

The National Snow and Ice Data Center (NSIDC) is part of the world's largest watershed. Cooperative Institute for Environmental Science Research at the University of Colorado. Boulder

Tiny valleys near the top of the Antarctic ice cap reach temperatures of nearly -100 degrees Celsius, according to a new study published this week (June 25) in 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 reviewing data from several Earth observation satellites, temperatures of -93 degrees Celsius (-135 degrees Fahrenheit) at several locations on the East Antarctic Plateau, a high snowy plateau in central Antarctic which 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 it needed a clear, persistent sky 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 even further, until clear, calm and dry conditions degrade and the air mixes with the air and water. warmer air 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 of -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 temperatures could drop a bit if conditions lasted several weeks, but this is highly unlikely.

The high altitude of the Antarctic Plateau of the East and its proximity to the South Pole give it the coldest climate on Earth. 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 MODIS instrument data aboard NASA's Terra and Aqua satellites, as well as data from NOAA polar operational meteorological satellites.

Researchers observed surface temperatures consistently falling 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 in this region can sometimes have 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 rates are very slow as surface temperatures approach the recorded values. Conditions do not persist long enough – it can take weeks – for temperatures to plummet below record levels. However, the temperature measured by the satellites is the temperature of the surface of the snow, and not the air above. Thus, the study also estimated the air temperature using nearby automatic weather stations and satellite data.

Interestingly, even though the coldest sites spanned hundreds of kilometers, the lowest temperatures were almost identical. This leads them to wonder if there is a limit to the cold on the set.

Using the difference between satellite measurements of the lowest snow temperatures in Vostok and three automated stations, and air temperatures at the same place and 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 also developed a set of instruments designed to survive and operate in the coldest places during the winter and measure both the snow and the temperature of the sea. 39; air. They plan to deploy the instruments in the next year or two, during the Antarctic summer when temperatures are relatively mild -30 degrees Celsius (-22 degrees Fahrenheit).

Source: Ted Scambos, NSIDC / Cover Images