Snow depth controls palsa growth

When a young palsa has risen sufficiently above a mire (bog) and has developed steep sides, drifting snow collects against these sides and inhibits freezing of adjacent ground. Measurement of the temperature regime on the top surface, and at the foot, of the northern edge of a 2.6 m high palsa in Utsjoki, Finland supports this hypothesis. The minimum temperature recorded in the winter of 1992–93 on the uncovered palsa summit was −23.4°C. After snowfall, the temperature stayed at +0.1°C at the foot of the palsa for over six months, until 20 June 1993. At the edge of the palsa, thick snow cover prevents the establishment of permafrost.