Why Is the Sky Pink in Winter in AK

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Pink sky in January in Interior Alaska

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In December and January, the daylight in Interior Alaska is salmon pink. Thus, when you see an OOTD outfit photo taken in the Arctic in winter on a clear day, it looks like someone applied a kitschy filter or like you are looking thru pink colored shades. But actually these pinkish colors are the natural beauty of winter in the sub-Arctic. This post explains the phenomenon and features a new look of the day. Read why the sky is pink.

Contents

What Is The Physics behind the Color of the Sky?
Air Pollution Can Be a Cause For Why the Sky Is Pink
Why to Wear Sunglasses When the Sky Is Pink
Is It Dark All Winter In Alaska
References

What Is The Physics behind the Color of the Sky?

When you live in mid-latitudes, you may have seen pink skies only during sunrise and sunset. However, at high latitudes, in winter, the sun barely comes above the horizon. Like in mid latitudes during sunrise/set, the sun beams have to travel a very long way thru the atmosphere at in Polar Regions in winter. This long distance increases the likelihood that visible light beams are scattered by gases.

graphic of length of the path a sun beam travels thru the atmosphere — At solar noon, the distance that a beam travels thru the atmosphere is the shortest (blue arrows). When the Sun is low in the sky, the light travels a comparably longer distance thru the atmosphere (red arrows) even though the distance Earth-Sun is about the same (dotted line). Consequently, the light can be scattered at more gas molecules.

The visible light ranges from ultra violet over blue, green, yellow, orange to red. You can see this when light is split into its components by a prism or the raindrops of a rainbow.

Rayleigh Scattering: Pink vs. Blue Sky

The atmospheric molecules scatter UV and blue light over and over again (Rayleigh Scattering). This makes the sky look blue when the Sun is high above the horizon. Then the distance that the light travels thru the atmosphere is relatively short. It is the shortest at solar noon, when the Sun is in the zenith. However, at low sun zenith angle during sunrise/set in mid- and low latitudes, the light travels a long distance thru the atmosphere. The blue frequencies are scattered away. Only the orange and red frequencies of the sun beam reach the eyes. Thus, everything seems to be in a light reddish-orange hue. In Fairbanks during daylight in winter, the Sun is very low in the sky. Like in mid- and low latitudes during sunrise/set, the light has to travel a long way thru the atmosphere.

Schematic view explaining Rayleigh scattering — The blue color of the sky is caused by Rayleigh scattering of sunlight by the gases in the Earth’s atmosphere. CC BY-SA 3.0 via Wikimedia Commons. The above image shows the degree to which Rayleigh scattering scatters blue light more intensely than red light. The scattering curve shown is calculated for sunlight passing vertically through the atmosphere and is based on Buchholtz (1995). Other details, such as scattering from dust and absorption of some light by greenhouse gases are not shown.

Air Pollution Can Be a Cause For Why the Sky Is Pink

You can also see read skies in Alaska during times of severe wildfires and volcanic eruptions. These events lead to the emission of particles of various size. Aerosols can also build naturally in the air by gas-to-particle conversion. They are also emitted from anthropogenic sources. The more particles/aerosols are in the atmosphere, the deeper the orange and red become. The aerosols scatter the light as well. Consequently, during air pollution from wildfires or when ash from volcanic eruption is in the air, the Sun may look red and the sky orange.

Pastel pinks mean relatively few, saturated orange and reds comparatively more aerosols.

seemingly pink trees in Interior Alaska — Pink trees due to the low sun zenith angle in December and January in Interior Alaska.

Why to Wear Sunglasses when the Sky Is Pink

Think of these beautiful sunrises and sunsets above the ocean. Like over the ocean, you also have a lot of glare as the snow also reflects the light. This glare is the reasons why there is no problem to find nice sunglasses in Alaska. Sunglasses sell like hotcakes.

In Polar Regions, you really need polarized sunglasses year round.

Is It Dark in Alaska All Winter?

At winter solstice, the Sun is still 2^o above the horizon in Fairbanks at noon. There are about 3:42 hours of daylight on December 21. However, you only have to drive north, maybe a seven hour drive, depending on the road conditions, to Wiseman (67°26′0″N 150°5′40″W) on December 21 to have no sunrise. In Utqiagvik (formerly Barrow), the farthest north Alaskan community, the polar night starts on November 18. The Sun remains below the horizon for 66 (!) days. The Sun rises again on January 22 at 1:16 PM, just to set again at 2:02 PM. This means after 66 days of darkness, Utqiagvik has about 46 minutes of pink light, if the sky is cloud-free!
On the contrary, at Amatignak Island (in the Aleutian Chain), which is the southernmost point of Alaska (51.262222 N, 179.108611 W), daylight and night conditions are more comparable to those in Leipzig, Germany (51.3397 N, 12.3731 E), London, UK (51.5074 N, 0.1278 W) or Calgary, Canada (51.0447 N, 114.0719 W).