Amplified bioproductivity during Transition IV (332 000–342 000 yr ago): evidence from the geochemical record of Lake El'gygytgyn
1Climate Impacts Research Centre (CIRC), Umeå University, 98107 Abisko, Sweden
2University of Cologne, Institute of Geology and Mineralogy, Zuelpicher Str. 49a, 50674 Cologne, Germany
3GeoForschungsZentrum Potsdam, Section 3.3, Telegrafenberg, 14473, Potsdam, Germany
*now at: School of Geography and Geosciences, University of St Andrews, St Andrews, Fife KY16 9AL, Scotland
Abstract. To date, terrestrial archives of long-term climatic change within the arctic region have widely been restricted to ice cores from Greenland and, more recently, sediments from Lake El'gygytgyn in Northeast Arctic Russia. Sediments from this lake contain a paleoclimate record of glacial-interglacial cycles during the last three million years. Low resolution studies at this lake have suggested that changes observed during Transition IV are of greater amplitude than any observed since. In this study, geochemical parameters are used to infer past climatic conditions thus providing the first high resolution analyses of Transition IV from a terrestrial arctic setting. These results demonstrate that a significant shift in climate was subsequently followed by a rapid increase in biogenic silica production. Following this sharp increase, bioproductivity remained high, but variable, for over a thousand years. This study reveals differences in the timing and magnitude of change within the ratio of silica to titanium (Si/Ti) and biogenic silica (BSi) records that would not be apparent in lower resolution studies. This has significant implications for the increasingly common use of Si/Ti data as an alternative to traditional BSi measurements.