Scientists reviewing over thirty years worth of data from a series of Earth observing satellites have found the coldest region on the planet. A thousand kilometer long ridge on the East Antarctica Plain has temperatures plummeting down to a blistering -93.2° Celsius, over 30° colder than the lowest temperature recorded in the coldest permanently inhabited town, in Siberia. The ridge lies between two peaks, Dome Argus and Dome Fuji, at an altitude of almost fourteen thousand feet – almost half as high as the peak of Mount Everest.
Ted Scambos, lead scientist at the National Snow and Ice Data Centre in Boulder, Colorado, had been studying snow dunes in Antarctica, vast dunes sculpted and polished by the Antarctic wind. As he looked closer at satellite imagery, he found that the snow between dunes was cracked, and speculated that as the temperature fell to new lows, the snow surface had shrunk and split. This led them to wonder just how cold it gets, so they began sifting through the accumulated data in thirty two years of observations from the Moderate Resolution Imaging Spectroradiometer (MODIS) instruments on NASA’s Terra and Aqua satellites and the Advanced Very High Resolution Radiometer (AVHRR) on several National Oceanic and Atmospheric Administration satellites. Having identified the frigid ridge between Dome Argus and Dome Fuji as the coldest region, they then narrowed the search by examining the area with the high resolution Thermal Infra-red Sensor (TIRS) aboard Landsat 8 to find the precise locations of the very lowest temperatures.
Anybody who has ever sat motionless under the open sky late at night has noticed how cold and dew-soaked it can get. Dew forms on a surface when it becomes cold enough to condense water vapour out of the air. This means that the surface has to be colder than the air itself, which happens due to radiative cooling. Thanks to the laws of thermodynamics, any object radiates its heat energy outwards in all directions. Objects on Earth normally receive as much heat from neighbouring objects (and even the sky itself) as they lose, but at night under a clear sky their heat energy has a clear path out to the vacuum of space. This happens all over the world, but conditions in Antarctica are special: Not only does the long Antarctic winter allow the ground to cool continuously for months without any exposure to the Sun to warm things up again, but the altitude is so high that there is very little insulating air between the ground and space.
As the ground chills, it cools the air directly above it, which then sinks, flowing downhill. This supercooled air then settles into various hollows on the ridge, further cooling the ground in those spots, adding the final ingredient to creating such numbing cold. “By causing the air to be stationary for extended periods, while continuing to radiate more heat away into space, you get the absolute lowest temperatures we’re able to find,” Scambos said. “We suspected that we would be looking for one magical site that got extremely cold, but what we found was a large strip of Antarctica at high altitude that regularly reached these record low temperatures.”
NASA’s Landsat 8 satellite was built at NASA’s Goddard Space Flight Centre in Greenbelt, Maryland, and launched on 11 February, 2013. It records hundreds of images every day of the Earth’s surface, and these images are distributed online as a free resource for the public. “With Landsat 8, we expect to see more accurate and more detailed maps of the landscape than we’ve ever been able to see,” said James Irons, the mission’s project scientist at Goddard. “If change is occurring, I think we’ll be able to detect it earlier and track it.”
“What we’ve got orbiting Earth right now is a very accurate and consistent sensor that can tell us all kinds of things about how the land surface of Earth is changing, how climate change is impacting the surface of Earth, the oceans of Earth, and the icy areas of Earth,” Scambos said. “Finding the coldest areas on Earth is just the beginning of the discoveries we’re going to be able to make with Landsat 8.”