<strong class="journal-contentHeaderColor">Abstract.</strong> Knowledge about timing, amplitude and spatial gradients of Holocene environmental variability in the Circum-Baltic region is key to understand its responses to ongoing climate change. Based on a multi-dating and proxy approach, we reconstruct changes in productivity from TOC contents in sediments of Lake Kälksjön (KKJ) in west-central Sweden spanning the last 9612 (+255/-144) years. An exception is the period from AD 1878 until today, in which sedimentation was dominated by anthropogenic lake level lowering and land use. In-lake productivity was higher during periods of warmer winters with shortened ice cover and prolonged growing seasons. A multi-millennial increase in productivity throughout the last ~9600 years is associated with progressively warmer winters in north-western Europe, likely triggered by the coinciding increase in Northern Hemisphere winter insolation. Decadal to centennial periods of higher productivity in KKJ correspond to warmer winters during a more positive North Atlantic Oscillation (NAO) polarity, as reconstructed for the last 5200 years. In consequence, we assume our decadal to centennial productivity record from KKJ sediments for the complete ~9600 years to provide a qualitative record of NAO polarity. A shift towards higher productivity variability at ~5450 cal. a BP is hypothesized to reflect a reinforcement of NAO-like atmospheric circulation variability, possibly driven by more vigorous changes in North Atlantic deep water formation.
Markus Czymzik, Rik Tjallingii, Birgit Plessen, Peter Feldens, Martin Theuerkauf, Matthias Moros, Markus J. Schwab, Carla Nantke, Sylvia Pinkerneil, Achim Brauer, Helge W. Arz
Markus Czymzik, Rik Tjallingii, Birgit Plessen, Peter Feldens, Martin Theuerkauf, Matthias Moros, Markus J. Schwab, Carla Nantke, Sylvia Pinkerneil, Achim Brauer, Helge W. Arz
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