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In some ways, the Arctic Circle is an imaginary place.

It includes a very real ocean with floating sea ice and caribou who move across the permafrost.

The four million people who live within the circle also exist. The chilly winter wind is also real.

But unlike a landmass you can point to, the Arctic Circle is not defined by physical borders.

It's an imaginary circle of latitude around 66 degrees north.

It's a circle that slices the top of the world and runs through eight countries, including the U.S.,

and it is undergoing real and profound change.

But before we talk about how climate change is

affecting the circle north of 66 degrees and the greater polar region we call the Arctic, how it's

warming four times faster than the rest of the planet and what it's like to witness changes

to one of the last wild places, we'll share what it was like to be there when its

cold climate was stable. A naturalist describes his youthful experience in the Arctic and what he

saw when he returned 30 years later. Welcome to Big Picture Science. I'm Molly Bentley,

and this episode is The Amazing Arctic.

The Arctic is a place of immense landscape and sky is how John Waterman described the area that he first journeyed to in 1983.

He has worn a lot of fleece hats during his years working and traveling through the Arctic.

He was a park ranger at Denali National Park, part of the Alaska Range, south of the Arctic Circle.

He is a photographer and author who has traveled extensively through our frozen north solo on foot

and by kayak on the No Attack River in the gates of the Arctic National Park.

So to help us appreciate the wildlife and conditions that may be slipping away, which he documents in the book into the thaw,

we asked John first to take us there. So imagine you've stepped out of

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