permafrost
Definition
Noun: A thick subsurface layer of soil or bedrock that remains at or below the freezing point of water (0°C or 32°F) for two or more consecutive years. It is a defining characteristic of polar and some alpine regions.
Usage
"Permafrost" is an uncountable noun. It refers to the frozen ground itself, not the act of freezing. It is typically used in scientific, environmental, and geographical contexts.
Examples
- Construction in the Arctic is challenging due to the presence of permafrost.
- Scientists are studying how thawing permafrost releases greenhouse gases.
- The pipeline was built on special supports to prevent it from melting the permafrost underneath.
Advanced Usage
- Active layer: The top layer of soil above permafrost that thaws during the summer and refreezes in winter.
- Plant roots are confined to the active layer above the permafrost.
- Permafrost thaw/degradation: The process of permafrost warming and melting, often due to climate change.
- Coastal erosion is accelerating because of permafrost degradation.
Variants and Related Words
- Cryosphere (n): The frozen water part of the Earth system, which includes permafrost, ice sheets, glaciers, and sea ice.
- Tundra (n): A vast, treeless Arctic region where the subsoil is permafrost.
Synonyms
- Frozen ground
- Permanently frozen soil
Related Phrases/Concepts
- Subsea permafrost: Permafrost located beneath the seabed on continental shelves, a remnant from the last ice age.
- Methane hydrates are stored in subsea permafrost.
- Permafrost carbon feedback: A climate change feedback loop where warming thaws permafrost, releasing stored carbon (as CO₂ and methane), which causes further warming.
- The permafrost carbon feedback is a major concern for climate models.
Noun
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ground that is permanently frozen
