Let's walk back in time... 🔄⏰ We're venturing into the U.S. Army Cold Regions Research and Engineering Laboratory’s Permafrost Tunnel to learn about permafrost. Permafrost is any soil, rock, ice or organic matter that has stayed frozen for at least two years – but it's often frozen for hundreds or even thousands. Permafrost is under much of Alaska and northwestern Canada, but that frozen ground is thawing due to climate change. With scientists in the field and research aircraft flying overhead, @nasa scientists are studying how permafrost thaw is impacting the Arctic and boreal forests. Video description: A male scientist wearing a hardhat opens a large freezer door in the mountainside to enter the Permafrost Tunnel. The tunnel is dug into hillside, the floor is dusty and the walls are packed dirt and rock with several supports and strings of lanterns lighting the tunnel. As he walks through the tunnel, he points out large brown wedges of ice frozen in the surrounding soil and rock. The video cuts to other features in the tunnel, like 18,000 year old animal bones, grasses, ice wedges, silt layers and an alder branch that's over 43,000 years old. The scientist continues walking through the tunnel, explaining that as we walk further in and down, we're moving "back in time" to see the older material that was frozen and preserved in the permafrost.