Part 1—Permafrost Primer
Introduction to PermafrostThe purpose of Part 1 is to give you a short introduction to permafrost. As you complete this section, keep the following key questions in mind so that you have a context in which to examine, visualize, and grasp the implications of the data you will use in the remainder of the chapter.
- What is permafrost?
- Where is permafrost found?
- Why is permafrost important to study and understand?
- What happens as permafrost thaws?
What is Permafrost?
Permafrost is defined as ground whose temperature is below the freezing point (i.e., 0 degrees Celsius or 32 degrees Fahrenheit) for two or more years in a row. The contents of the ground could be soil, sediment, or rock. The layer of ground between the permafrost and the surface is called the "active layer", or "seasonally frozen ground". This layer thaws and freezes seasonally to about one meter in depth.
Where is Permafrost Found?most of the land in Antarctica is covered by the massive Antarctic ice sheet. However, it is certainly cold enough for permafrost to form in Antarctica.
For more information and photographs visit: NSIDC All About Frozen Ground
Why is Permafrost Important to Study?
Scientists around the world are studying permafrost to learn how it is changing. The process of studying frozen permafrost temperature trends involves placing thermistors into boreholes drilled into the Earth. It is cold, dirty work! In the photo to the right scientists in northern Norway are drilling a borehole.
Learn more about this project at Thermal State of Permafrost in Norway and Svalbard
What Happens as Permafrost Thaws?
Infrastructure is impacted
As permafrost thaws, the active layer becomes thicker, and the landscape may change. The ground can become weak. Structures built on previously frozen but currently-thawing ground can shift as the ground under them moves and sinks. This movement can cause significant cracking and instability in structures. Examine the images (right) of building structures in Chersky and Alaska to see examples of these effects. (Click on the images for a larger view.)
The landscape changes
When frozen ground thaws, the environment can change dramatically. For example, thawing permafrost on mountain slopes can lead to landslides.
When permafrost thaws on level ground, it can buckle the ground. Trees growing nearby can be at risk. Sometimes, their roots become so weak that trees tilt and fall over. These trees are sometimes called a "drunken forest" because they look like they are stumbling every which way, like a drunken person trying to walk.
In areas near coasts, permafrost and sea ice work together to protect the shore from ocean waves. When sea ice melts away and permafrost thaws, waves hitting the shore can damage the land and lead to erosion. Sometimes, the land collapses into the ocean.
Carbon is released
In this video, Polaris Project scientist Katey Walter ignites the methane that is released when the surface of a frozen lake is punctured.
As permafrost thaws, previously frozen plant and animal matter decays, releasing carbon dioxide and methane into the atmosphere. Permafrost contains a large amount of plant and animal material, so it could release a large amount of carbon dioxide and methane into the atmosphere. The accelerated release of greenhouse gases contributes to increasing surface air temperatures, triggering further thawing, and subsequently the release of additional gases, which will cause more atmospheric warming, and so on. This cycle is an example of positive climate change feedback.