This dataset provides counts of chironomid head capsules for the MIS 5a sediment sequence retrieved from Sokli (Finland) in 2010. Counts per taxon are presented against depth (m). The chironomid dataset provides information on MIS 5a ecosystem dynamics and was used to quantitatively reconstruct climate conditions (Helmens et al., 2021). A total of 43 samples were selected for chironomid analysis. The samples were treated with warm KOH (10%) to de-flocculate the material and subsequently rinsed through a sieve with a 100-µm mesh. Chironomid head capsules (HCs) were hand-picked from the residue using a Bogorov sorting tray and mounted on permanent microscope slides using Euparal mounting medium. HCs were identified using Brooks et al. (2007). The top sample as well as the bottom three samples had very low count sums and these were left out of the dataset prior to further analysis. The final dataset presented here contains 39 samples. The analyses were performed in the laboratories of the University of Helsinki, Finland.

Further funding was provided by SKB (Swedish Nuclear Fuel and Waste Management Company) and the Bolin Centre for Climate Research.