Climatic and environmental changes reflected by lake-level fluctuations at Gerzensee from 14,850 to 13,050 yr BP

Abstract

High-resolution sediment analysis at Gerzensee, Swiss Plateau, focused on the reconstruction of lake-level changes during the last glaciation Greenland Stadial 2a (GS-2a) and a large portion of Lateglacial including the Gerzensee oscillation. The chronology is derived from a comparison of the oxygen-isotope stratigraphy established at Gerzensee with that of the NGRIP ice core. On a multi-millennial scale differences between the lake-level and oxygen-isotope records established from cores GEJ–GEK reflect a complex interplay among climate, vegetation and lake level during retreat of the ice sheet. But on a multi-centennial scale both the lake-level and oxygen-isotope records show a general agreement, i.e. cool periods such as Greenland Stadial GS-2a and Greenland Interstadials-1d and -1b, which coincided with more positive water budgets and, conversely, warm periods (Greenland Interstadials-1e and -1c) with more negative water budget. This is in agreement with the regional pattern of palaeohydrological changes reconstructed from previous studies. Despite possible reduced annual precipitation during GS-2a, the maintenance of relatively high lake-level conditions at Gerzensee at this time could have resulted from reduced evaporation and stronger runoff on bare slopes, whereas during the Lateglacial Interstadial the phases of lake-level lowering may have been associated with summer dryness linked to increasing summer insolation.