Field Notes · Ice
Polar daylight: what 24-hour sun does to a schedule
Above the Arctic Circle the day is a variable that can take any value from zero to twenty-four hours, and it changes by the week. Here is what the geometry does, what it does to sleep, and how the Daylight Simulator turns it into a plan.
The earth is tilted at 23.4 degrees, which is why there are seasons and why anywhere above 66.6 degrees of latitude has at least one day a year when the sun does not set and one when it does not rise. Longyearbyen at 78 degrees has four months of each. Ilulissat at 69 has two months of midnight sun and about six weeks of polar night. The Antarctic Peninsula at 65 degrees never quite reaches either but gets close in December, when the sun dips for a couple of hours and the sky stays bright.
The speed of change
The strange part is not the extremes but the transitions. Around the equinoxes, the day length at 78 degrees changes by about forty minutes a week. A traveller who arrives in Svalbard on 10 March has a short day with a low sun; one who arrives on 10 April has fifteen hours of light. The Daylight Simulator draws this as a chart of weeks around your date, and the chart is the reason to be precise about dates in the polar realm in a way that does not matter at the equator, where the day is twelve hours every day of the year.
What it does to sleep
Nobody sleeps properly in the midnight sun. The light through the curtain at two in the morning tells the body it is afternoon, and the town’s habit of a walk at midnight makes it worse. The practical answers are an eye mask, a routine tied to meals rather than to the sky, and acceptance. In the polar night the problem inverts: the body wants to sleep at three in the afternoon, and the answer is a head torch, bright indoor light in the morning and the same routine tied to meals.
What it does to the plan
In the light season everything is possible at any hour and the guides use it: boat trips that leave at ten in the evening, the walk to the icefjord at midnight when the bergs go pink. The photographs that people bring back from Ilulissat are mostly taken between eleven and one at night. In the sled season, March and April, the light is the resource: low, long, gold from early morning to late afternoon, and gone by seven. The plan books the long trips in the middle of the day and keeps the evenings for the sauna.
The Antarctic version
Ships on the peninsula in December run on nearly twenty hours of light, and the expedition teams use it: a landing at six in the morning, a Zodiac cruise at nine at night, the ice going pink behind the stern at half past eleven. The passengers stop sleeping and do not seem to mind. The Journey Simulator for the peninsula shows the daylight per day, and in midsummer the number is the reason the trip feels twice as long as its calendar.
Questions people ask
When exactly does the sun not set in Svalbard?
From about 20 April to 22 August in Longyearbyen. The polar night, when it never rises, runs from about 26 October to 15 February. The Daylight Simulator gives the dates for any latitude.
Is the polar night completely dark?
No. In November and January there is a blue twilight at midday; in December there is not. The aurora, the moon on snow and the town’s lights make it a strange, beautiful season rather than a black one.
