The Polar Night is a natural phenomenon where the sun remains below the horizon for a continuous period exceeding 24 hours. This seasonal shift occurs exclusively within the Earth’s polar regions, north of the Arctic Circle and south of the Antarctic Circle. Svalbard, a Norwegian archipelago situated deep within the Arctic Ocean, is one of the most accessible places to experience this extended darkness. Its main settlement, Longyearbyen, serves as the reference point for charting this unique period where the sun’s absence alters the daily rhythm of life.
What Defines Polar Night?
Polar Night is an astronomical event caused by the planet’s axial tilt, approximately 23.5 degrees relative to its orbital plane. During the Northern Hemisphere winter, the Arctic is tilted away from the sun, causing the sun’s path to drop entirely below the horizon. This period of continuous darkness occurs anywhere above the Arctic Circle, located at roughly 66.5 degrees North. The duration of the Polar Night increases progressively the closer one travels toward the geographic North Pole.
The phenomenon is defined as the period when the sun’s center never rises above the horizon over a 24-hour cycle. Due to atmospheric refraction, the sun’s disc is still visible when its center is slightly below the horizon, making the actual period of continuous darkness slightly shorter than the theoretical duration. This definition marks the transition from twilight to a period where the sun is absent entirely. Regions near the Arctic Circle experience this for only a few days, while the poles endure a dark period lasting roughly six months.
The Duration of True Polar Night in Svalbard
Svalbard’s main town, Longyearbyen, is located at approximately 78 degrees North, placing it far inside the Arctic Circle. This northern position results in one of the longest dark periods in any permanently inhabited settlement. The sun officially dips below the horizon around October 26th and does not reappear until approximately February 15th of the following year.
The total duration of the sun remaining below the horizon in Longyearbyen is about 113 consecutive days. This period encompasses the entire winter season, where the landscape is continuously bathed in the unique light conditions of the Polar Night. The high latitude of the archipelago is the primary factor determining this extended length.
Distinguishing Between Night and Twilight
Despite the sun being below the horizon for 113 days, not all of that time is spent in total darkness. This distinction is based on the angle of the sun below the horizon, which defines three stages of twilight. The darkest phase is the astronomical night, which occurs when the sun is more than 18 degrees below the horizon and is generally only experienced at latitudes closer to the Pole.
Longyearbyen mostly experiences the Civil Polar Night, which runs from approximately November 14th to January 29th. During this period, the sun is between six and twelve degrees below the horizon, meaning there is no civil twilight. However, at midday, a faint blue glow from nautical twilight is often visible on the southern horizon, preventing absolute darkness.
Life and Adaptation in Perpetual Darkness
The absence of a regular light-dark cycle presents a challenge to the human body’s internal clock, or circadian rhythm. The primary environmental cue for regulating this rhythm is light, and its lack can delay the timing of sleep and activity patterns. Studies show that the secretion of melatonin, the sleep-regulating hormone, can be delayed during the Polar Night, but a rhythmic pattern is generally still maintained.
While true Seasonal Affective Disorder (SAD) is reported to be rare among residents, many experience symptoms like fatigue and changes in mood or sleep quality. Residents often rely on artificial light therapy and a strong social community to maintain their daily structure. The town adapts by becoming a haven for viewing the Northern Lights, which are frequently visible during the long nights.
Wildlife in Svalbard has developed strategies to cope with the extreme conditions of the perpetual night. Research shows that the Arctic Ocean remains a highly active ecosystem, contrary to the assumption that marine life becomes dormant. Zooplankton and tiny organisms continue to feed and reproduce, supporting seabirds like auks and guillemots that forage in the deep twilight.
The Svalbard reindeer, a subspecies endemic to the archipelago, shows adaptation to the darkness. Their eyes possess an adaptation that allows them to utilize more ultraviolet light, helping them discern plants beneath the snow in low-light conditions. They also change their internal clock, or circadian rhythm, to a much shorter cycle of feeding and resting, rather than adhering to a strict 24-hour pattern.