Permafrost facts
Alaska like most areas in high latitudes or many areas at high altitude has large areas of continuous or discontinuous permafrost. Permafrost or so-called cryotic soil is defined as soil that remains at temperatures at or below 32F (0oC) for two or more consequent years. Permafrost occurs on 24% of the land in the Northern Hemisphere. It also occur on the ocean floor of the shelf of the Arctic Ocean. Permafrost holds about 0.22 per mille of the Earth’s total water.
How to recognize permafrost in the taiga
The active layer is a layer that thaws in spring and re-freezes in fall. Due to the permafrost underneath, water can not percolate in deeper than the bottom of the active layer. Thus, trees growing on permafrost cannot root deep. Consequently, in these areas, spruce trees look very under-nutritioned and remain small (see photos above and below). Often only blueberries or scrubs can grow. The ground may be very moist during summer.
Permafrost and construction
When you build a house, street or path on permafrost, the construction conducts heat thawing some of the ground underneath. The melt-water may evaporate or run away laterally. Since the water originally was part of the soil matrix, the ice loss leads to shrinking of the ground thickness. The construction sinks and may deform.
When there is a large ice-lens in the permafrost, a large whole can form seemingly over night when the thawed water finds a way to escape.
Best practice is to avoid construction on permafrost or provide good insulation to the ground and/or build on stalks.
Spread the word by tweeting Learn to recognize permafrost when you see it.
You can find another post on permafrost damage /a>, and posts on Alaska phenomena like faults and pink light in winter.
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OOTD – summer work outfit
This outfit features a sheath dress dressed down with an utility jacket and low heel pumps. The scarf adds a pop of color, but picks up the color of the jacket and pumps. Thus, the color becomes part of the look that overall has a neutral feel color wise.
Photos: N. Mölders, G. Kramm
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