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摘要
A 12 m long lacustrine record from Sokli, N Finland, was analyzed for diatoms, non-pollen palynomorphs, macrofossils, pollen and geochemistry in order to reconstruct the development of a high-latitude Eemian lake and investigate the influence of climatic and environmental changes on the lake ecosystem. Based on this multi-proxy dataset we distinguished five major lake phases in the lake's evolution. An initial minerogenic, glacio-lacustrine phase was followed by an organic-rich early Eemian lake phase characterized by anoxic bottom waters, high seasonality and rising nutrient levels. A long open water season, pronounced summer stratification and high productivity characterized the following early mid-Eemian lake phase, corresponding to the Eemian thermal maximum. During the late mid-Eemian lake phase decreasing water depths due to infilling and extensive mixing of the water column resulted in less stable summer stratification and decreased anoxia. The late-Eemian lake phase was characterized by shallow and dynamic conditions and a cooling climate. Superimposed on these general trends are two events characterized by colder and more arid conditions, that possibly match cold and arid events registered in palaeolimnological records on the European continent. In general, the multi-proxy record reflects a nutrient rich lake, where changes in mixing regime associated with climatic forcing and lake level changes asserted a major impact on the aquatic assemblages. The changes in the aquatic assemblages reflect the major patterns of climate change that took place during the Eemian in northern Europe; i.e. a rapid warming and high seasonality during the early Eemian, decreased seasonality during the mid Eemian and a cooling late Eemian with increased seasonality. The high latitude Sokli Eemian palaeolake record lengthens the latitudinal extent of Eemian terrestrial records across Europe, adding to the understanding of climatic gradients and drivers over Europe.
- 出版日期2016-12-1
