Even Winter Light Changes For Inuit b/c of Climate Shift, Temp. Inversions

"Inuit have no word for twilight. For centuries, people felt no need for such a word in the Arctic communities where the sun stays in the sky all summer and disappears below the horizon all winter. New vocabulary became necessary in the past few years, however, as hazy light started lingering on the southern horizon deep into the months when the sky normally would contain nothing but stars.

Residents of Nunavut struggle for words when asked to describe the phenomenon. "It's like dawn," said Marty Kuluguqtuq, a municipal worker in Grise Fiord. "It's like a glimmer on the horizon." Philip Manik, a board member for the Hunters and Trappers Association in Resolute Bay, 1,700 kilometres south of the geographic North Pole, said the light has grown steadily brighter over the past decade. "Right now, the horizon is rainbow-coloured. It covers almost the whole horizon, even at the darkest time of year."

At first, scientists were skeptical about the natives' reports of unnatural brightness in winter. Climate data showed the Arctic getting warmer, and the rules of physics suggested that such low-density air would make the winter darkness even more profound. But the sliver of light at the edge of the sky grew brighter each year, and locals kept calling the weather station in Resolute Bay for some kind of explanation. "A lot of Inuit were reporting this across the North, which contradicted my original thinking," said Wayne Davidson, a fluent speaker of Inuktitut and the town's Environment Canada station operator for nearly two decades.


EDIT

Mr. Davidson guessed the strange twilight is a mirage, a little-known effect of climate change in which thermal inversions carry light from the South into the dark North. He tested the theory by floating a weather balloon into the sky in Resolute Bay on a November day more than a week after the winter night began, and the sky showed an unnatural glow. The balloon recorded the temperature near the ground at -27. Climbing to 285 metres, it warmed up to -15, and at 657 metres it reached -12. "That's a very steep inversion, one of the steepest I've ever measured." With help from the Dutch physicist Siebren van der Werf, Mr. Davidson developed a detailed explanation: The sharp difference between the cold air on the ground and the warmer air above makes a prism that reflects light hundreds of kilometres away.

EDIT

http://www.theglobeandmail.com/servlet/story/RTGAM.20041202.wxtwilight02/BNStory/specialScienceandHealth/

because the sun runs nearly parallel to the horizon, it takes ages to dip very far below it - which is when twilight is. There's a calulator here

eg In Barrow in December, civil twilight (sun between 0 and 6 degrees below the horizon) lasts between 3 and 4.5 hours each day. Compare that to Miami, where you get less than half an hour before sunrise, and less than half an hour after sunset. In November, Barrow gets 6 hours a day.