Oxygen isotope values of precipitation and the thermal climate in Europe during the middle to late Weichselian ice age

The oxygen isotope compositions of 28 mammoth tooth enamel samples from Estonia, Latvia, Lithuania, Poland and Denmark provide new quantitative records of the middle to late Weichselian climate in northern Europe. The new δ18O data was combined with records of oxygen isotope values from earlier investigations on European mammoth tooth enamel and palaeogroundwaters to study the spatial patterns and temporal variations in the oxygen isotope composition of precipitation and the thermal climate over much of Europe. The reconstructed geographical distribution of δ18O in precipitation during 52–24 ka reflects the progressive isotopic depletion of air masses moving northeast, consistent with a westerly source of moisture for the entire region, and a circulation pattern similar to that of the present-day. Regional long-term average δ18Ow values were 0.6–4.1‰ lower than at present, the largest changes recorded for the currently maritime influenced southern Sweden and the Baltic region. The application of regionally varied δ/T-slopes, estimated from palaeogroundwater data and modern correlations, yield reasonable estimates of glacial surface temperatures in Europe and imply 2–9 °C lower long-term mean annual surface temperatures during the glacial period.