The appearance of blue clouds over Antarctica came substantially earlier this year, and had, in fact, tied for the earliest time noctilucent clouds were spotted over the South Pole since NASA first started tracking data on the clouds.
Noctilucent clouds, or night-shining clouds, usually appear in late November or early December. According to NPR, these are wispy clouds that shine a bluish-white light when viewed from the ground but appear in a far more intense shade of blue when viewed from space. About a decade ago, NASA had launched a satellite that is capable of snapping photos of the ice crystals that form these clouds and based on the space agency’s data, those blue clouds appeared over Antarctica much earlier than usual, with the first sighting this year recorded in mid-November.
Satellite images posted Friday on NASA’s website show that noctilucent clouds were first seen over Antarctica on November 17, and the clouds forming between that date and November 28. This is based on the agency’s Aeronomy of Ice in the Mesosphere (AIM) spacecraft, which was deployed in 2007 in an effort to determine the ins and outs of this unusual event in the South Pole, and to further understand Earth’s mesosphere, which can be found about 50 miles above the surface, separating our atmosphere from outer space.
In an article posted on the NASA website and written in 2003, University of Colorado professor Gary Thomas explained the history of the noctilucent blue clouds that form over Antarctica.
“Noctilucent clouds are a relatively new phenomenon. They were first seen in 1885,’ about two years after the powerful eruption of Krakatoa in Indonesia, which hurled plumes of ash as high as 80 km into Earth’s atmosphere.”
In another NASA blog post cited by the Christian Science Monitor, the agency’s Lina Tran explained that the clouds provide scientists with information regarding the mesosphere’s links to other atmospheric, weather, and climate features. They normally appear in the summer and can be seen over the Arctic in July and August. Conversely, the phenomenon takes place in Antarctica in November and December, and Tran added that that’s the time of the year when the mesosphere is at its most humid, but also when it is the “coldest place on Earth,” with temperatures reaching as low as minus 210 degrees Fahrenheit.
Tran also explained why noctilucent clouds appear as blue clouds when seen above Antarctica, and even more so when observed from space. She said that the “shocking blue” hue is a result of the clouds reflecting sunlight, and of space dust from disintegrating meteors seeding the clouds.
A third NASA article, published in December 2013, explained that noctilucent clouds, or NLCs, have spread out to other parts of the world, and aren’t mainly restricted to polar regions anymore.
“In recent years NLCs have intensified and spread. When noctilucent clouds first appeared in the 19th century, you had to travel to polar regions to see them. Since the turn of the century, however, they have been sighted as close to the equator as Colorado and Utah.”
With AIM having spotted the blue clouds forming over Antarctica much sooner than usual, scientists believe this may have something to do with an “earlier seasonal change at lower altitudes,” according to Phys.org.
“Winter to summer changes in the Antarctic lower atmosphere sparked a complex series of responses throughout the atmosphere – one of which is an earlier noctilucent cloud season,” the publication wrote.
“In the Southern Hemisphere, AIM has observed seasons beginning anywhere from Nov. 17 to Dec. 16.”
Another possible theory behind the earlier appearance of the blue clouds in Antarctica this year is the continuing presence of greenhouse gases in the atmosphere, wrote Gizmodo Australia.
[Featured Image by NASA/Getty Images]