Increased aridity during the early Holocene in West Greenland inferred from stable isotopes in laminated-lake sediments

Abstract

Palaeoclimatic inferences from the Greenland ice cores suggest that Holocene climate was relatively uniform. The ice core records primarily reflect hemispheric temperature-related climate processes whereas lakes tend to reflect regional scale climatic variability. Stable isotopes in closed-basin lakes are sensitive to changes in effective precipitation. Here we report stable isotope evidence (δ 18O and δ 13C records from authigenic calcite in laminated lake sediments) from two oligosaline, closed-basin lakes in southern West Greenland (Søndre Strømfjord). The stable isotope profiles indicate a dynamic early to mid-Holocene climate as a strongly negative precipitation-evaporation balance from ∼7000 to 5600 cal yr BP lowered lake levels throughout the region. This interpretation of the stable isotope data is supported by a survey of modern lake-water isotopic composition and fossil shorelines around many closed-basin saline lakes which indicate higher lake levels in the past. The increased aridity during the early Holocene resulted from a shift in regional circulation patterns in the Davis Straits–Baffin Bay area. Enhanced stability of the West Greenland depression and the situation of a regional trough over the Søndre Strømfjord area caused weakened westerly airflow and strengthened outflow (i.e. winds blowing off the ice sheet), resulting in reduced precipitation in the region. Decreased precipitation, coupled with higher insolation, probably caused the negative precipitation–evaporation balance.