One of the main problems with lake sediment drilling are drilling disturbances and gaps between individual core meters. In order to fill such gaps, we drilled all cores of the ELSA-20 in duplicate, with an offset of 0.5 m between the cores. The ISRS670 (see below) Corg(chlorins) data have been measured with mm resolution for both overlapping cores to fill gaps with a Dynamic Time Warp approach.
The resultant continuous organic carbon record reveals climate oscillations, which are well known from the Greenland ice, where the warm phases, called interstadials, have been dated precisely by annual layer counting of the ice (snow) layers. The ages from the Greenland ice were applied to the respective sections of the ELSA-20 record to arrive at a stratigraphy fully comparable to the Greenland ice chronology.
The other parameter measured along with Corg(chlorins) was the silicium and aluminium content in the sediments. The Si/Al ratio is an established proxy for the abundance of diatoms, which are the main producers of Corg(chlorins) in a lake system. Accordingly, both ELSA-20 proxies are related to diatom production. These algae are on maximum abundance only during warm intervals. The ELSA-20 is accordingly a time series of warm temperatures in central Europe. The climate evolution of central Europe follows exactly the temperature changes in the Greenland ice, which represent the hydrographic changes of the North Atlantic.
All ELSA-20 data were measured with subannual resolution, then smoothed with a three point running mean, and finally resampled to a continuous annual resolution.