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46 The Viking Age in Denmark

Draved Mosc

Prollle 1959

Figurę 10 Fluctuations in the degree ofhumification (to the left) in Draved bog, south Jylland, and the frequency of two species of watcr-loving plants (to the right). (After Aaby)

Greenland, where the ice-cap contains an extremely long record (Fig. 9).² So-called oxygene-isotope studies of temperaturę fluctuations have demonstrated a elear congruence - on the level of medium-sized frequencies — between the variations in temperaturę on Greenland and thosc of post-medieval north-west Europę. The movements on the low-frequency level — periods of morę than 200 years — are also parallel to each other; but herc there is a time lag of about 250 years between Greenland and, for instance, England (after 1100), which has the best