How and how well do recent varved lake sediments reflect temperature and precipitation in Central Finland?

Annually laminated (varved) lake sediments are an important proxy for reconstructing past climatic changes. Advantages of using varve records, which potentially extend thousands of years back in time, include their seasonal resolution and precise time control. The seasonally resolvable structure enables studies of short term changes in detail. It is known that climatic changes can be reflected in boreal varve records although their manifestation in each varve record is case specific. Varve characteristics are affected not only by climatic parameters but also environmental factors and human actions and climatic signal can be subdued, masked or enhanced by other factors operating in the lake catchment. However similarities in the response of varve characteristics to climate signal are expected. Yet there are only few studies considering how and which varve characteristics respond to variations in climatic parameters. How reliable could the conclusions drawn from varve data be? The objective of this study is to shed light on how and how well clastic-organic varves record climate parameters, such as temperature and precipitation. Are there common features between different lakes and is there any statistical relationship between climate and varve parameters? Seven lake sediment sequences, which are annually laminated until present day, were studied in Central Finland area. Varve records were reconstructed for last 120 years and compared with data from nearest meteorological stations. The focus was set on temperature and precipitation as they are believed to be the most important climatic factors affecting varve characteristics in the study area. Visual and statistical methods were used to compare the results. If the relationship between certain varve character and meteorological parameter is demonstrated, it can be used to extend climatic knowledge from varve chronologies thousands of years back in time.