Late Holocene climate and environmental changes in Kamchatka inferred from subfossil chironomid record.

摘要

This study presents a reconstruction of the Late Holocene climate in Kamchatka based on chironomidudremains from a 332 cm long composite sediment core recovered from Dvuyurtochnoe Lake (Two-YurtsudLake, TYL) in central Kamchatka. The oldest recovered sediments date to about 4500 cal years BP. Chironomidudhead capsules from TYL reflect a rich and diverse fauna. An unknown morphotype of Tanytarsini,udTanytarsus type klein, was found in the lake sediments. Our analysis reveals four chironomidudassemblage zones reflecting four different climatic periods in the Late Holocene. Between 4500 andud4000 cal years BP, the chironomid composition indicates a high lake level, well-oxygenated lake waterudconditions and close to modern temperatures (w13 �C). From 4000 to 1000 cal years BP, two consecutiveudwarm intervals were recorded, with the highest reconstructed temperature reaching 16.8 �C betweenud3700 and 2800 cal years BP. Cooling trend, started around 1100 cal years BP led to low temperaturesudduring the last stage of the Holocene. Comparison with other regional studies has shown that terminationudof cooling at the beginning of late Holocene is relatively synchronous in central Kamchatka, SouthudKurile, Bering and Japanese Islands and take place around 3700 cal years BP. From ca 3700 cal years BP toudthe last millennium, a newly strengthened climate continentality accompanied by general warmingudtrend with minor cool excursions led to apparent spatial heterogeneity of climatic patterns in the region.udSome timing differences in climatic changes reconstructed from chironomid record of TYL sediments andudlate Holocene events reconstructed from other sites and other proxies might be linked to differences inudlocal forcing mechanisms or caused by the different degree of dating precision, the different temporaludresolution, and the different sensitive responses of climate proxies to the climate variations. Furtherudhigh-resolution stratigraphic studies in this region are needed to understand the spatially complexudpattern of climate change in Holocene in Kamchatka and the surrounding region.ud�