Abstract

A high-resolution sedimentary record in the Vichuquen basin is key for studying recent atmosphere-ocean dynamics as well as recent anthropogenic activity (e.g. sea-level variability and biogeochemical changes). We have reconstructed the recent variability of the lake using diatom functional groups (e.g. planktonic, benthonic, epiphytic) as environmental indicators. Located along coastal central Chile, Lake Vichuquen (~35ºS, 72ºW; 4 m asl, 30 m deep, surface area15 km2) has a local climate heavily influenced by the coupled atmosphere-ocean-land system (SWW, SPA, ACC, the Ma. This site is ideally located to monitor past AMOC changes with North Atlantic Drift waters at the surface and NADW in the deep. Besides the interglacial/glacial cycles, higher frequency oscillations are recorded in both the planktonic G. ruber (white) and benthic Cibicidoides sp. stable isotope records. The benthic δ 13C values indicate nearly continuous NADW presence and confirm a strong AMOC, also during most of the glacial periods. Varying surface water conditions, especially during the younger interglacial periods, are reflected in the G. ruber isotope data and appear to be linked to salinity changes since they are not recorded in the alkenone sea-surface temperature data. Although glacial stages Gi 2 and Gi 4 show the expected higher benthic δ 18O values, Gi 6 was the glacial period with the strongest impact on the AMOC as revealed by cooler, less ventilated surface waters and a less ventilated NADW. Overall, the AMOC was strong throughout, but experienced high frequency oscillations at a level similar to the middle Pleistocene interglacial periods.