6.3 Groundwater in Permafrost Settings

At the cold extremes of the globe, permafrost forms in groundwater systems (Figure 44). Permafrost can be soil, rock or sediment that is saturated or unsaturated, but by definition is frozen for more than two consecutive years.

World map of the cryosphere (the frozen water part of the Earth system).
Figure 44 – World map of the cryosphere (the frozen water part of the Earth system). The distribution of permafrost is shown in purple hues (Ahlenius, 2007).

Where the surface is free of ice, permafrost occurs beneath the “active layer” which is soil, rock or sediment that freezes and thaws each year. Active groundwater flow occurs above and below the permafrost layer which is essentially impermeable. This obstacle to downward drainage causes the surface to be boggy. When substantial volumes of water flow into the groundwater system, areas of unfrozen ground occur within the permafrost (Figure 45).

Figure and photograph showing the ocurrence of permafrost
Figure 45 – Permafrost is frozen portions of subsurface near the Earth’s surface: a) schematic of the variable distribution of frozen and unfrozen material with less frozen material where surface water seeps into the subsurface or forest cover insulates the ground; b) photo of a thin active layer above the permafrost on the North Slope of Alaska (photo by Kling, 2012).


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