As we approach spring, the arctic gradually comes out of its long winter night. And as polar winters get milder and milder every year, people started noticing something unusual: the Sun sometimes rises on the wrong day—and in the wrong place.

The polar sunrise happening weeks too early isn’t quite a new phenomenon. It’s called the Novaya Zemlya effect, from the name of an island in the far north of Russia where it was documented as early as the 1500s.

Air close to the ground there is extremely cold, especially after the ice has spent months in the winter dark. So it can sometimes happen that the air higher up is warmer. If you’ve ever looked at the tail of a plane in an airport, you’ve surely noticed that warm air bends light differently than cold air (it has a lower refraction index if you want to get fancy about it).

If the difference in temperature between cold and warm air is enough (which only happens in the extreme polar cold), the difference in how much light is bent makes the boundary between the two layers reflect light that comes from some angles below.

In the Novaya Zemlya effect, for example, it reflects the light from the Sun, making it appear to be above the horizon some days (or even a couple of weeks) before it actually rises for the first time. It’s an upside-down version of a classic mirage: instead of showing down on the ground a blurry reflection of the sky above, the polar mirage shows in the sky the reflection of something below it.

Cool, but what does climate change have to do with this? Rising temperatures in the atmosphere make the conditions for this curious mirage more likely. It’s unclear to what extent climate change is affecting the phenomenon, but it seems very likely to play a role. And though it’s far from the most dangerous of its effects, pushing the date of arctic sunrise sure is one of the most striking.

If you want more

• A similar story was told, with a bit more poetry, on This American Life 
• The basic effect is similar to what happens if you look up at certain angles when under water, or inside optic fibers [INTERNAL LINK].

Cover photo: CC0 Markus Distelrath/pixabay