Scientists have discovered the coldest place in the world
The National Snow and Ice Data Center (NSIDC) is part of the Cooperative Institute for Research on Environmental Sciences at the University of Colorado Boulder
Tiny valleys near the Antarctic ice sheet reach temperatures of almost -1
After spotting data from several Earth observation satellites, scientists announced in 2013 that they have found a surface temperature of -93 degrees Celsius at several locations on the East Antarctic Plateau, a high snow-capped plateau in central Antarctica that covers the South Pole includes. This preliminary study has been revised with new data showing that the coldest locations actually reach -98 degrees Celsius. Temperatures are mainly observed during the southern polar night in July and August.
When the researchers first announced that they had found the coldest temperatures on earth five years ago, they discovered that persistently clear skies and light winds are needed for temperatures. But the new study adds a twist to the story: not only is clear sky necessary, but the air must also be extremely dry, as water vapor blocks the heat loss from the snow surface.
The researchers observed the ultra-low temperatures in small depressions or shallow depressions in the Antarctic ice sheet, where cold, dense, descending air gathers above the surface and can remain there for several days. This allows the surface and the air above it to continue to cool until the clear, quiet and dry conditions collapse and the air mixes with warmer air in the atmosphere.
"In this area, we see periods of unbelievably dry air, and this makes it easier to radiate heat from the snow surface into space," said Ted Scambos, senior scientist at the National Snow and Ice Data Center at the University of Colorado Boulder and lead author the study.
According to the researchers, the record of -98 degrees Celsius is about as cold as it is possible to reach the Earth's surface. For the temperature to be so low, clear skies and dry air must persist for several days. Temperatures could be a little lower if conditions lasted for several weeks, but that's extremely unlikely, Scambos said.
The high altitude of the East Antarctic Plateau and its proximity to the South Pole give it the coldest climate in any region of the world. The lowest air temperature ever measured by a weather station (-89 degrees Celsius) was measured there in July 1983 at the Russian station Wostok.
But weather stations can not measure temperatures everywhere. For example, in 2013, Scambos and his colleagues decided to analyze data from several Earth observation satellites to see if they found even lower temperatures on the plateau than in Vostok.
In the new study, they analyzed satellite data from the winter of the Southern Hemisphere between 2004 and 2016. They used data from the MODIS instrument aboard NASA's Terra and Aqua satellites, as well as data from NOAA's Polar Operational Environmental Satellites. The researchers observed that snowmelt temperatures regularly dropped below -90 degrees Celsius (-130 degrees Fahrenheit) almost every winter in a wide region of the plateau, more than 3,500 meters (11,000 feet) above sea level. Within this broad region, they found dozens of locations that were much colder. Nearly 100 sites reached surface temperatures of -98 ° C.
The atmosphere in this region can sometimes have less than 0.2 mm of total water above the surface. But even when it's so dry and cold, the air catches some of the heat and sends it back to the surface. This means that the cooling rates are very slow as the surface temperatures approach the recorded values. The conditions do not last long enough – it could take weeks – until the temperatures fall below the observed levels. The temperature measured by satellites, however, is the temperature of the snow surface, not the air above it. The study also estimated air temperatures using nearby automatic weather stations and satellite data.
Interestingly, although the coldest locations were spread over hundreds of miles, the lowest temperatures were almost all the same. That made them wonder, is there any limit to how cold it can get on the plateau?
Using the difference between the satellite measurements of the lowest snow temperatures in Vostok and three automated stations and the air temperatures at the same location and time, the researchers concluded that the air temperatures at the very coldest locations (where there are no stations) are probably -94 Degrees Celsius or about -137 degrees Fahrenheit.
The research team has also developed a set of tools to survive and measure winter temperatures in the coldest places and to measure both the temperature of snow and that of air. They plan to use the instruments over the next year or two in the Antarctic summer, when temperatures are comparatively mild -30 degrees Celsius.
Credit: Ted Scambos, NSIDC / Cover Images