A1 Journal article – refereed
A late Holocene record of solar-forced atmospheric blocking variability over Northern Europe inferred from varved lake sediments of Lake Kuninkaisenlampi

List of Authors: Saija Saarni, Francesco Muschitiello, Stefanie Weege, Achim Brauer, Timo Saarinen
Publication year: 2016
Journal: Quaternary Science Reviews
Volume number: 154


This study presents a new varved lake sediment sequence from Lake Kuninkaisenlampi, Eastern Finland.
The record is constituted by alternations of clastic and biogenic laminae and provides a precise chronology
extending back to 3607 ± 94 varve yrs. BP. The seasonality of the boreal climatic zone, with cold
winters and mild summers, is reflected in the varve structure as a succession of three laminae from
bottom to top, (i) a coarse to fine-grained detrital lamina marked by detrital catchment material
transported by spring floods; (ii) a biogenic lamina with diatoms, plant and insect remnants reflecting
biological productivity during the season of lake productivity; and (iii) a very fine amorphous organic
lamina deposited during the winter stratification. The thickness of the detrital lamina in the lake reflects
changes in the rate of spring snow melt in the catchment and is, therefore, considered a proxy for winter
conditions. Hence, the record allows reconstructing local climate and environmental conditions on interannual to the multi-centennial timescales. We find that minerogenic accumulation reflected in the
detrital lamina exhibits a high multi-decadal to centennial-scale spectral coherency with proxies for
solar activity, such as D14C, and Total Solar Irradiance, suggesting a strong link between solar variability
and sediment transport to the lake basin. Increased catchment erosion is observed during periods of low
solar activity, which we ascribe to the development of more frequent atmospheric winter blocking circulation
induced by solar-forced changes in the stratosphere.We suggest that soil frost in the catchment
of Lake Kuninkaisenlampi related to more frequent winter blocking led to increased surface run-off and
ultimately to increased catchment erosion during spring. We conclude that, during the past ca 3600
years, solar forcing may have modulated multi-decadal to centennial variations in sedimentation regimes
in lakes from Eastern Finland and potentially in other North European lakes.

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