What is polar night?

ByKieran Mulvaney

Published February 1, 2024

In the HBO detective series True Detective: Night Country, a pair of police officers seek to solve mysterious deaths in the fictional Alaska town of Ennis against the backdrop of the long, cold polar night. 

But what exactly is the polar night? Where does it occur and why? And what does it mean for the people and wildlife who live through it?

Where polar night occurs 

Simply put, polar night refers to a period of time when the Sun does not rise above the horizon for more than 24 hours. It occurs in winter north of the Arctic Circle and south of the Antarctic Circle, which are circumpolar lines at latitude 66.6 degrees North and South respectively. The closer to the poles, the longer polar night lasts: at the North Pole, for example, the Sun sets a few days after the autumnal equinox in mid-September and does not rise again until mid-March, giving the top of the world a polar night of 179 days. Farther from the poles, polar night can occur for just 24 hours or so over the course of the winter solstice.

The Alaska town of Utqiagvik, the most northerly settlement in the United States and seemingly the one on which True Detective’s Ennis is modeled, experiences approximately 65 days of polar night each year, lasting from mid-November to mid-to-late January.

Despite its name, polar night is not one continuous block of pure nighttime. Sunlight is refracted over the horizon even when the sun has set, and so at many latitudes, most days may in fact be dominated by different phases of “polar twilight.”

As with anywhere else on Earth, the middle of the day can be lighter than other times as the Sun ascends toward and falls away from the horizon without ever rising above it: “civil twilight” may provide enough light for people to carry on with their outdoor activities, while “astronomical twilight” is so dark that the only natural lights are stars, the Moon, and the aurora borealis that dance and flicker across a clear sky.

Such semantics do little, however, to alter the fact that for those living in the Arctic (or the few residing at research stations in Antarctica), the polar night can be a profound challenge.

What is it like to live through polar night? 

The absence of familiar cues and day-night cycles can affect circadian rhythms and disrupt sleep, and the perpetual lack of daylight often saps energy. However, living through the long polar night is not universally miserable, and many residents embrace the experience. As one inhabitant of Svalbard, a Norwegian archipelago in the Barents Sea region, explained to NPR: “You have to see the beauty in [the darkness]. And to me, that’s not hard at all … I kind of feel even more immersed by nature when I walk out into the darkness.”

Arctic denizens do what they can to counter the long night blues, from using light therapy lamps that replicate the wavelengths of sunlight to simply maintaining routines, keeping physically active, and engaging in as many social pursuits as possible–although the latter two options are limited by the fact that the long twilight is accompanied by core-chilling cold.

January minimum temperatures in Utqgiavik, for example, average –18 degrees F, while the Norwegian municipality of Kautokeino recently saw the mercury drop below minus 40 on its coldest night in 25 years.

It isn’t just human inhabitants who have to adapt to the cold and the dark.

On land, lemmings and voles bury deep into the snowpack to feast on seeds left over from the previous year, while Arctic ground squirrels choose to hibernate and even polar bears may hunker down through the worst of winter,  a behavior known as “shelter denning.” Many animals adjust their daily rhythms, feeding and sleeping in small chunks of time throughout the day to conserve energy.

The eyes of reindeer shine blue in winter, an adaptation that enables them to find the lichen on which they feed more easily in months of darkness. In the sea, zooplankton continue their daily migration from deeper waters to the surface by following the light from the Moon.

Not immune to climate change 

Even the dark, cold polar regions feel the effects of climate change–which ironically, has been bringing both more and less light to the polar night. Sea ice thinned by warming temperatures is allowing more ships to pass through, and the accompanying light pollution may be affecting the behavior of marine organisms more than 600 feet below the surface.

And in some parts of the Arctic, such as Svalbard, warmer temperatures have led to reduced snow cover and even winter rain, making the darkest and most challenging of seasons even darker and more difficult to live in.

>>> Read full article>>>
Copyright for syndicated content belongs to the linked Source : National Geographic – https://www.nationalgeographic.com/environment/article/polar-night-arctic-antarctic