ICE-WEDGE REJUVENATION, FOSHEIM PENINSULA, ELLESMERE ISLAND, CANADA

Ice wedges with multiple growth stages and complex wedge systems are d escribed for six sites on the Fosheim Peninsula. Recent rates of later al wedge growth, inferred from tritium concentrations within the ice, are 2-5 mm a-1. One factor responsible for ice wedge rejuvenation in t his area is colluviation on low-angled slope segments by slopewash, so lifluction and active-layer detachment processes or by mudflow within retrogressive thaw slumps. The most complex section examined was at th e base of a long slope where colluvial deposits overlay peat. Epigenet ic and syngenetic wedges of at least two and possibly three different ages were present as a result of sedimentation rates estimated to be 4 -25 mm a-1. The second factor producing wedge rejuvenation is variabil ity in summer climate, and this is responsible for the development of the uppermost growth stages at all actively cracking sites. The deepes t thaws in the past 45 years were hind-cast for 1960 and 1962 so that more than 25 years of aggradation had taken place by the time of field work. More generally, it can be shown that there is a significant prob ability that secondary wedges will be present during any period withou t regional climatic change. For the Eureka summer climate, the probabi lity is 0.2 that a secondary wedge at least 5 cm high and 10 years old will be observed at any randomly exposed section. Thus field observat ion of widespread secondary growth stages is not necessarily an indica tion of recent climatic change but may be due to normal climatic varia bility.