Late Pleistocene climate of Poland in the mid-European context

Abstract

Proxy data from pollen and mollusc indicator species, periglacial phenomena, changes in geometry of mountain palaeoglaciers and based on selected lithological and geomorphological features enabled reconstruction of the Late Pleistocene climate characteristics in Poland and adjacent areas. Climate during the Eemian was generally stable but with a distinct west-east gradient in summer. Strong influence of the Atlantic air masses moving to the east resulted in the annual precipitation over 600 mm. Climate instability in the late Eemian as well as during stadials and interstadials of the Early Weichselian was expressed by progressive cooling and increasing temperature difference between winters and summers, reflecting stronger continentalism towards the west, accompanied by decreased precipitation. Periglacial frost crackings and polygonal patterns indicated occurrence of permafrost in Poland already at about 49 ka BP and its occurrence until the termination of the last glaciation. These periglacial structures have developed at mean annual temperatures from −9 to −4 °C, with winter extremes up to about −25 °C. Mean summer temperature reached likely around 10 °C as suggested by palaeobotanic record. Palaeoglaciological studies of mountain glaciers across Europe allowed inferring their activity and sensitivity to climatic fluctuations during the Late Weichselian. The Weichselian of central Europe was controlled mostly by the southerly and easterly circulation dominated by climate cyclones and anticyclones, respectively. An inflow of air masses from the west was significantly limited and concentrated mainly within the so-called periglacial corridor between the Scandinavian ice sheet and the Alps. Such circulation pattern determined serious reduction of precipitation during the Last Glacial Maximum that reached 60% in relation to modern conditions. The following Late Pleistocene cold phases (Oldest and Younger Dryas) were slightly warmer and wetter with increasing contribution of the westerlies that were strongly dependent on progressing shrinkage of the Northern Hemisphere ice sheets.