A thick subsurface layer of soil that remains frozen throughout the year, occurring chiefly in polar regions.
- ‘Most of the remainder comes from wetlands, gas hydrates, permafrost, and termites.’
- ‘In some areas, thawing of permafrost will improve infiltration.’
- ‘It's estimated that a quarter to a third of all soil carbon is locked in permafrost.’
- ‘However, there may be water locked in permafrost in some deep polar craters.’
- ‘However, permafrost covered large northern areas and many habitats were fragmented and displaced southward.’
- ‘A species of bacterium locked in Alaskan permafrost for 32,000 years woke up and started swimming as soon as its medium melted.’
- ‘The forest grows atop permafrost, a layer of soil that remains frozen year-round.’
- ‘On Alaska's northern coast, they met Native Alaskans dealing with melting permafrost and coastal erosion.’
- ‘But most of it is under tundra permafrost, if not indeed under even more inhospitable terrain.’
- ‘Hot, dry summers have thawed permafrost layers and shriveled berry crops.’
- ‘The permafrost below the topsoil is frozen all year around, and this prevents roots from penetrating deeply into the ground.’
- ‘These self-organized patterns result from the effects of freezing and thawing on layers of stone and soil overlying permafrost.’
- ‘These climates introduced permafrost and cold-climate weathering products to river systems.’
- ‘The rest of the year what little soil there is on the surface is rock hard above permafrost.’
- ‘Increased snow and ice melt have caused higher rivers while thawing permafrost has wreaked havoc with roads and other infrastructure.’
- ‘In many high mountains regions, permafrost may be present.’
- ‘In the north soil takes the form of permafrost, where the water in the ground is permanently frozen.’
- ‘It's springtime in Siberia, where slumbering mammoths are emerging from melting permafrost.’
- ‘In regions influenced by permafrost, water migrates along the thermal gradient from warm to cold, thereby feeding ice in the frozen core.’
- ‘We are already beginning to see the likely effects of climate change: melting permafrost and the retreat of permanent icepacks.’
1940s: from permanent + frost.
We take a look at several popular, though confusing, punctuation marks.