Across the Arctic, winter can seal entire lakes beneath thick ice and snow. From above, everything appears silent and motionless.
But beneath some of those frozen surfaces, bubbles continue rising from the mud. They contain methane created as microorganisms consume organic material released from thawing permafrost.
In this episode of Beyond the Frozen Horizon, we descend beneath a thermokarst lake to discover how frozen ground collapses into water, how carbon stored for thousands of years can become active again, and why an Arctic lake can continue breathing long after winter appears to have shut it down.

The Arctic is losing ice. But the consequences do not end at the coastline.
New geodetic measurements suggest that as enormous masses of ice disappear from the polar regions, the solid Earth beneath them is responding. The poles are rising faster, the equatorial region is sinking, and our planet is subtly changing shape.