Late-Holocene climatic changes as detected by the growth and decay of ice wedges on the southern shore of Hudson Strait, northern Quebec, Canada

The dating of cryoturbated palaeosols associated with past ice-wedge activi ty on late-Holocene sandy fluvial terraces in a region of continuous permaf rost leads to an interpretation of periods of ice-wedge growth and active c racking that alternated with periods of decay, dormancy and active layer de epening. The reconstruction corresponds with palaeoclimatic information obt ained from existing Arctic-wide and regional proxy records. The 'Little Ice Age' stands out as a period of intense ice-wedge activity in the study are a. It was followed by a warm thawing interval during the first half of the twentieth century. From AD 1946 to 1991, a well-documented cooling of the c limate took place, which reactivated 94% of the studied ice wedges. The pyr amidal shape of ice-wedge tops and the depths of the upgrowth features coul d be correlated between sites several kilometres apart, clearly indicating a regional climatic response. The mean annual air temperature dropped from about -7.8 degreesC in 1946 to -8.9 degreesC in 1991. The threshold tempera ture for active ice wedges probably lies within this range.