Anthropogenic versus climatic control in a high-resolution 1500-year chironomid stratigraphy from a southwestern Greenland lake

Abstract

We performed a high-resolution study of chironomid assemblages in a sediment core retrieved from Lake Igaliku in southern Greenland. The well-dated core is located within the former Norse Eastern Settlement and covered the last 1500yr. The comparison of chironomid stratigraphy (PCA axis scores) with instrumental temperature data, land use history and organic matter in the sediment over the last 140yr suggested that the primary changes in chironomid fauna in 1988±2yr were driven by the shift to modern agriculture in the catchment. This unprecedented change in chironomid fauna was most likely triggered by a shift in in-lake processes. Within the instrumental period, subtle variations in the chironomid assemblages that occurred before 1988±2yr were significantly correlated with summer temperatures even in times of traditional extensive sheep farming in the catchment. The relevance of the chironomid-derived climate signal over the last 1500yr was supported by its good concordance with previous studies in west Greenland and in the Arctic. The chironomid assemblage therefore appeared to be a valuable proxy for climate changes within the Norse colony area. Synchronous changes in Norse diet and chironomid-reconstructed climate give new insights into the interplay of Norse society with climate.