Thermally induced movements in ice-wedge polygons, western Arctic coast: Along-term study

Thermally induced seasonal movements of the active layer and subjacent perm afrost have been measured in numerous ice-wedge polygons that have varied i n age, type, crack frequency, and topographic location. The field observati ons show that, in winter, thermal contraction, which is inward, is constrai ned or vanishes at the polygon centres but, in summer, thermal expansion, w hich is outward, is unconstrained at the ice-wedge troughs. Therefore, ther e tends to be a small net summer transport of the active layer, to varying depths, into the ice-wedge troughs. The movement has been observed in all p olygons studied. The slow net transport of material into the ice-wedge trou ghs has implications for: permafrost aggradation and the growth of syngenet ic wedges in some troughs; the palaeoclimatic reconstruction of some ice-we dge casts; and the interpretation of polygon stratigraphy based upon the as sumption that the polygon material has accumulated in situ.