Comparison of changes in vegetation in northeast Greece with records of climate variability on orbital and suborbital frequencies over the last 450 000 years

A new direct pollen–orbital tuning procedure, based on a correspondence between changes in certain vegetation elements and March and June perihelion configurations, is applied to the Tenaghi Philippon record, northeast Greece. The development of a refined chronological scheme allows comparisons to be made with records of climate variability from the North Atlantic as well as of global sea level/ice volume and atmospheric CO2 content. On orbital frequencies, the comparison reveals a close correspondence between relative ice volume extent and tree population size during glacial intervals. During interglacial and interstadial periods the degree of forest development is more closely associated with high-latitude insolation and related climate regimes rather than extent of residual ice volume. On suborbital frequencies, the Greek record shows similar repeat times in peaks of steppe vegetation with North Atlantic ice-rafting events, but the amplitude of this variability in the two records is not always proportional. Overall, what emerges is that the major shifts in the relative abundance of forest v. open vegetation communities at Tenaghi Philippon on orbital and suborbital frequencies over the last 450 000 years are coherent with high-latitude changes affecting atmospheric and oceanic circulation. Glacial decreases in atmospheric CO2 content contributed to the elimination of tree populations by exacerbating water stress conditions during arid intervals, but do not appear to be the primary driver of the observed vegetation changes at this latitude. Variations in CO2 levels (in the order of 40 ppmv) between different interglacial/interstadials periods with adequate moisture availability appear to have had a limited effect on the nature and size of tree populations.