Self, A.E.; (2010) The relationship between chironomids and climate in high latitude Eurasian lakes: implications for reconstructing Late Quaternary climate variability from subfossil chironomid assemblages in lake sediments from northern Russia. Doctoral thesis , UCL (University College London).

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Abstract

This thesis investigates climate variability during the Late Quaternary in northern Russia by analysis of subfossil Chironomid assemblages in lake sediment cores. The modern chironomid fauna was determined in surface-sediment samples from 94 lakes, located between 61° - 72°N and 52° - 131°E. The influence of chemical and physical environmental variables on the distribution and abundance of taxa was investigated using multivariate analysis and modelling of taxon responses. Chironomid distribution showed a statistically strong relationship to mean July air temperature and continentality, and inference models were developed to reconstruct these variables. Palaeoclimate reconstructions for the past 700 years are presented from lakes on the Putoran Plateau, western Siberia (68°N, 92°E). These reconstructions show that whilst July air temperatures have remained relatively stable over the last 50 years, continentality has declined, resulting in a longer growing season. The results also enabled the models to be validated against instrumental records. Reconstructions are then presented from lakes in north-east European Russia: Lake Kharinei, (67.36°N, 62.75°E) where sedimentation started approximately 12600 cal. yrs BP, and a mid-Holocene sequence (4500 – 6500 cal. yr BP) from VORK5 (67.86°N, 59.03°E). The chironomid-inferred reconstructions suggest the early Holocene was approximately 2°C warmer than present with a more continental climate. July air temperatures then declined but remained warmer than present until 6000 yrs BP. From approximately 6000 yrs BP, July temperatures declined and the climate became more continental, indicating a shift to short cool summers. Combined use of the July air temperature and continentality inference models enhances the explanatory power of the palaeoenvironmental reconstructions and helps to reconcile apparent discrepancies with other proxy records. The results improve our understanding of the nature and timing of climate change, such as the spatial extent of the Younger Dryas, in poorly-studied regions of northern Eurasia.

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