WHAT IS PERMAFROST?

Beneath the tundra, under Arctic soil, and locked inside subarctic mountain slopes lies one of Earth’s most misunderstood geological features: permafrost. You can’t see it from the surface. You can’t feel it underfoot on a warm summer hike. But permafrost shapes entire landscapes, supports ecosystems, and — as the climate continues to warm — poses one of the most consequential environmental challenges of our time.

So what exactly is permafrost, and why should you care?

The photographs above show permafrost cores, revealing layers of ice, sediment, and organic material preserved in frozen ground.

A BASIC PERMAFROST DEFINITION

Permafrost is ground that remains at or below 0°C (32°F) for at least two consecutive years. The definition is purely about temperature, not ice content. Permafrost can be dry, rocky, or saturated with ice; what matters is that it stays frozen, year-round, for at least two winters running.

It exists on every continent, including under the ocean floor in shallow Arctic seas, but it’s most widespread across:

  • Northern Canada, Alaska, and Russia
  • Greenland and Scandinavia
  • The Tibetan Plateau and high-altitude mountain regions
  • Antarctica

In many places, it has been frozen for thousands of years, creating a deep, long-lasting layer beneath the surface.

Roughly 25% of the Northern Hemisphere’s exposed land surface sits above some form of permafrost. In countries like Russia and Canada, that figure climbs much higher.

Permafrost helps shape entire ecosystems. It influences where forests can grow, where wetlands form, and how water moves across the land. In places with ice-rich permafrost, the ground can behave almost like a freezer, keeping ancient organic material (old plants and soils) preserved.

CONTINUOUS VS. DISCONTINUOUS PERMAFROST

Not all permafrost is created equal. Scientists classify it by how much of the land it underlies:

  • Continuous permafrost covers more than 90% of the ground in a given region, and is found in the high Arctic and interior Siberia.
  • Discontinuous permafrost exists in patches, often in subarctic regions where warmer microclimates allow some areas to remain unfrozen.
  • Sporadic and isolated permafrost appears in small pockets at the southern edges of permafrost zones; these are often the most vulnerable to disappearing entirely.
Permafrost vs. the Active Layer

The ground above the permafrost — called the active layer — thaws every spring and refreezes every fall. This is the zone where plants grow, where animals dig their burrows, and where most soil activity happens. The active layer can range from a few inches to several feet deep, depending on climate, soil type, and vegetation cover.

Below the active layer, the permafrost begins. In some parts of Siberia, it extends more than 1,500 meters (nearly a mile) into the earth. In other places, it’s a thin, fragile band just a few meters thick. In warming regions, those thinner zones are often the first to disappear.

Permafrost and Climate Change

This is where global attention has sharpened considerably. Permafrost soils store an enormous amount of organic carbon — the frozen remains of ancient plants, animals, and microbes that never fully decomposed. When permafrost thaws, that organic matter starts to decompose. Microbes wake up, begin breaking down the frozen material, and release carbon dioxide and methane into the atmosphere. This creates what scientists call a permafrost carbon feedback loop: A warming climate thaws permafrost, which releases greenhouse gases, which drives more warming, which thaws more permafrost.

Beyond carbon release, permafrost thaw causes serious physical changes on the ground:

  • Thermokarst formation: As ice-rich permafrost melts, the ground above it can collapse, forming uneven, waterlogged terrain riddled with sinkholes and lakes.
  • Infrastructure damage: Roads buckle, buildings tilt, and pipelines crack when the frozen ground they were built on starts to shift.
  • Coastal erosion: In Arctic communities, thawing coastal permafrost accelerates shoreline collapse, threatening villages that have existed for centuries.
  • Ecosystem disruption: Boreal forests, wetlands, and tundra habitats are being altered faster than species can adapt.

Learn More at the Churchill Northern Studies Centre

If you’re curious about permafrost, Churchill, Manitoba, is a fascinating place to learn. It sits at the meeting point of boreal forest and tundra, where seasonal freeze-thaw cycles, soil conditions, and Arctic warming all intersect in real time.

Want to go beyond definitions and actually see northern science in action? The Churchill Northern Studies Centre (CNSC) supports world-class research and offers educational programs for curious minds of all backgrounds. Whether you’re a scientist, student, or lifelong learner, Churchill puts you on the ground where this story is unfolding in real time.

Visit Churchill, Manitoba, and make CNSC your home base for exploration.

The CNSC is an independent, nonprofit field station working to understand and sustain the North. We provide accommodations, meals, equipment rentals, and logistical support to scientific and social researchers working on a diverse range of topics of interest in the subarctic. We also facilitate learning programs throughout the year for noncredit learning vacations, university credit courses, and youth programming.

Explore our Learning Vacations to see how you can experience the subarctic in a way that’s meaningful, personal, and unforgettable. Or, donate today to support greater understanding of — and deeper appreciation for — the natural, social, economic, and cultural environments of the North.