What is the characteristic of the soil in the arctic desert? What is Permafrost?

Due to the constant low temperatures, the soil in the Arctic desert is covered with permafrost and loses its fertility. Permafrost is formed mainly in the upper soil layer and reaches a depth of several meters to half a kilometer. This is a layer of frozen soil and ice that remained after the ice age in the Arctic. The soil, having saturated the water from the melting of glaciers and precipitation, froze. And, since now in these parts of the planet the summer is very short, and the temperature is almost always below zero, the underground ice does not melt.