Palsa Localities in Padjelanta National Park, Swedish Lappland

Abstract

Seven bogs adjacent to Puolejokk in Padjelanta, Swedish Lappland, contain palsas either in groups as low winding ridges, or as large isolated oval-shaped hummocks well above the surface of the bogs. In midsummer 1963, trenches 2 m long, 30 cm wide, were excavated down to the tjäle across several palsas in each of the four largest bogs. The thawed dark brown to dark reddish brown peat of each palsa rested on a frozen core of gray sand or of till. By mid-summer 1967, the previously trenched palsas had caved in, collapsed, or sunk beneath the water of the bogs.

Permanently frozen ground exists under better drained nonsorted polygon areas nearby, indicating a climate conducive for palsa maintenance, although the larger palsas may have reached a growth stage such that any slight disturbance might produce deterioration. Alternatively, larger undisturbed palsas may be collapsing in the wetter bogs due to water level changes.