Holocene climate history of Geographical Society Ø, East Greenland — evidence from lake sediments

Abstract

Sediment cores from two lakes in the outer coastal region of East Greenland were investigated for chronology, lithology, palynology, and biogeochemistry. A 10 m long sequence recovered in Basaltsø comprises the entire lake history following the last glaciation of the area, probably during the Preboreal oscillation. This is indicated by a succession from glacial via glaciolimnic to limnic sediments. Deglaciation of the area was associated with a high sedimentation rate, mirrored also in the basal part of a 2.6 m long core from a smaller lake (B1) about 1 km south of Basaltsø. Limnic sedimentation without glacial influence commenced about 10 000 cal. yr BP according to radiocarbon-dated terrestrial plant remains. Biogeochemical and palynological data indicate an early Holocene climatic optimum from 9000 to 6500 cal. yr BP A climatic deterioration began at 6500 cal. yr BP with an increase in snow accumulation, documented by a change in the pollen assemblage and a coinciding change in the grain-size distribution. At least since 5000 cal. yr BP, a decrease in the biogeochemical parameters in both lake sediment successions indicates a temperature decline. This deterioration culminated at about 3000–1000 cal. yr BP, when the climate was cold and dry. A slight warming is indicated in the pollen assemblage between ca. 1000 and 800 cal. yr BP. Following a subsequent rise in precipitation, cooling during the Little Ice Age is mirrored in lowest dwarf shrub pollen percentages and in low contents of organic components.