Holocene climate of the Kola Peninsula; evidence from the oxygen isotope record of diatom silica

Holocene climate variability was studied in a lake sediment record covering the last c. 9000 years from Lake Chuna on the Kola Peninsula, north-west Russia, using the oxygen isotope composition of diatom silica (delta(18)O(diatom)). The evaporation of the lake waters is likely to be minimal, and thus the isotopic composition of the lake waters recorded by the delta(18)O(diatom) reflects the isotopic composition of summer precipitation. Overall the delta(18)O(diatom) signal seems to record a predominance of the polar Arctic air mass bringing cold summer air temperatures immediately after the last glaciation and again after 4000 years to present time. The Atlantic maritime air mass is likely to have supplied warm summer rainfall especially in the mid Holocene. The pattern is broadly consistent with a quantitative pollen reconstruction from Chuna Lake which suggests higher mean July temperatures from deglaciation to 5500 years BP with a rather steep decline to lower temperatures after 4000 years BP. Our results support the general regional scenario of a mid Holocene warm period deduced from the higher tree line, vegetation changes and glacier fluctuations in Fennoscandia. However, the delta(18)O(diatom) record from the Kola Peninsula Suggests a relatively cold early-Holocene with a gradual shift to warmer conditions to a maximum at around 5000-4000 years BP assuming that the modern delta(precipitation)-temperature relationship has been constant throughout the Holocene. (C) 2004 Elsevier Ltd. All rights reserved.