Permafrost refers to a layer of soil or rock that is frozen all year round. Permafrost is found throughout much of Alaska, parts of Canada, and other countries in the far north. You might think a place with permafrost would be barren, but plants can still grow in the soil at the surface, which is not frozen during warmer parts of the year. However, there may be a thick layer of permafrost underneath. As air temperature rises, so does the temperature of the ground, which can cause permafrost to thaw (or melt).
What's happening now?
Ground temperatures have increased throughout Alaska since the late 1970s, and permafrost has already thawed in many places.
What will happen in the future?
As temperatures keep getting warmer, permafrost will continue to thaw. For example, the map on the right shows how permafrost in northwestern Alaska could change by the year 2100.
Why does it matter?
When permafrost melts, the land above it sinks or changes shape. Sinking land can damage buildings and infrastructure such as roads, airports, and water and sewer pipes. It also affects ecosystems. For example, the top photo shows a forest where the trees are leaning or falling over because the permafrost underneath them has melted.
Another reason to be concerned about permafrost is because it has a lot of carbon trapped inside. As permafrost thaws, this carbon is released to the atmosphere in the form of methane, a powerful greenhouse gas. This process leads to more climate change and is an example of a positive feedback loop, which happens when warming causes changes that lead to even more warming.