They are gas bubbles, little hiccups of methane that look magical when they're trapped in winter ice, but come the spring, those bubbles will loosen, get free, and like an armada of deep-water flying saucers, they will make their way to the surface. When the ice breaks they will pop and fizz into the air — and disappear.

Except they don't really disappear. Once they hit air, methane bubbles make trouble. How much trouble depends on how many bubbles get released all over the planet. In this one lake, there are thousands, tens of thousands of them, as you can see. But in the oceans, they are bigger — much bigger.