Surface abrasion of palsas by wind action in Finnish Lapland

Palsas at Lake Ahkojavri (69°35′N, 26°11′E), western Utsjoki, Finnish Lapland, display very marked effects of surface erosion. Mainly westerly winds have caused the removal of a layer of peat, in some cases more than 40 cm thick, from the palsa surface. The surface peat of one eroded palsa is radiocarbon dated to 2710±70 years BP. Many palsas with heights of 1.5–3 m are almost bare of vegetation. Cracks typical of vegetated palsa surfaces are either worn away or filled with wind-drifted peat. Erosion takes place in winter by wind-drifted snow and ice crystals abrading the peat surface. Some recently formed palsas have been found on the same palsa mires. They are located among the eroded mature palsas and range from 60 to 80 cm in height and 20 to 30 m2 in area. The new palsas also imply strong wind activity in winter. No unusual development in the depth of the active layer on palsas has been noticed. New permafrost is also found in small peat hummocks called pounus.