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Chironomid-based temperature reconstruction for the Eemian Interglacial (MIS 5e) at Sokli, northeast Finland

Plikk, Anna, Engels, Stefan, Luoto, Tomi P., Nazarova, Larisa, Salonen, J. Sakari, Helmens, Karin F.
Journal of paleolimnology 2019 v.61 no.3 pp. 355-371
Chironomidae, air temperature, climate, fauna, habitats, lakes, latitude, limnology, paleontology, sediments, Denmark, Finland, Scandinavia
The Last Interglacial (Eemian, MIS 5e) can be considered a test-bed for climate dynamics under a warmer-than-present climate. In this study we present a chironomid record from the high latitude Sokli site (N Finland), where a long continuous sediment sequence from the last interglacial has been preserved from glacial erosion. The chironomid-analysis shows a diverse fauna, with dominance of warm-water indicators and shifts in assemblage composition that can be attributed to temperature, lake depth, productivity and habitat availability. Quantitative mean July paleotemperature estimates based on the chironomid data indicate overall mean July air temperatures up to 1 °C warmer than present. Two cooling events can be discerned, the Tunturi event, dated to about 127.5 ka BP, in the lower part of the sequence, and the Värriö event, dated to about 119 ka BP, associated with the beginning of a cooling trend in the upper part of the record. Warm conditions already at the onset of the interglacial contrast with a recent chironomid-based last interglacial temperature reconstruction from Denmark, which suggests a late onset of Eemian warming. The relatively small increase in inferred temperatures compared to present day temperatures at Sokli differs from other high latitude Eemian sites, and likely reflects the influence of the Atlantic Meridional Overturning Circulation in maintaining already elevated temperatures in Fennoscandia during interglacials.