Circumpolar describes something that circles around one of Earth's poles, the North Pole or South Pole.

When astronomers talk about circumpolar stars, they mean stars that never dip below the horizon as Earth rotates. If you live in Alaska and watch the night sky, you'll see certain stars circle around the North Star without ever setting. These stars are circumpolar from your location. The farther north you live, the more stars become circumpolar. At the North Pole itself, half of all visible stars are circumpolar because they never sink below the horizon.

Scientists also use circumpolar to describe regions near the poles. The circumpolar Arctic includes the frozen ocean and lands surrounding the North Pole, home to polar bears, Arctic foxes, and Indigenous peoples who have thrived in extreme cold for thousands of years. Similarly, the circumpolar Antarctic refers to the continent and ocean around the South Pole.

Ocean currents can be circumpolar too. The Antarctic Circumpolar Current flows endlessly eastward around Antarctica, the only ocean current that circles the entire globe. It's the largest current on Earth, moving more water than all the world's rivers combined.