Qualitative changes in NAO polarity of the last 9600 years in total organic carbon contents of lake Kälksjön sediments

A total organic carbon (TOC) record covering the last 9600 years was measured from freeze-dried and homogenized samples of Lake Kälksjön (central Sweden) sediment core KKJ19 at 1 cm resolution using an EA Isolink elemental analyzer coupled to a DELTA V advantage isotope ratio mass spectrometer. Sediment core KKJ19 was retrieved from the deepest part of Lake Kälksjön in summer 2019 with a Niederreiter piston corer. TOC measurements were performed in August 2021. Main aim of the measurements was the establishment of a time-series of paleoenvironmental variability for the western Baltic region. A 2500-year low-pass filtered version of the record was subtracted from the original data. The filtered time-series indicates qualitative changes in NAO polarity.