Thursday, November 8, 2012

New paper shows European climate was warmer than 20th century during multiple periods over past 11,000 years

A new paper published in Climate of the Past reconstructs central European climate from oxygen isotopes in stalagmites and shows the climate was warmer than the 20th century during multiple periods over over the past 11,000 years. These periods include ~ 1000, 1800, 5000, 7000, 9000, 9500, 10000, and 10500 years ago. The paper also shows that the Little Ice Age was the coldest period of the past 11,000 years. 
Composite & smoothed data from the stalagmites in this study is shown by the red line. Thousands of years ago is indicated by the x axis. As indicated by the graph legend to the right side, lower values of the oxygen 18 isotope are associated with warmer climate. The Little Ice Age [LIA] was the coldest period of the past 11,000 years.
Clim. Past, 8, 1751-1764, 2012

Bunker Cave stalagmites: an archive for central European Holocene climate variability

J. Fohlmeister1, A. Schröder-Ritzrau1, D. Scholz2, C. Spötl3, D. F. C. Riechelmann4, M. Mudelsee5, A. Wackerbarth1, A. Gerdes6,7, S. Riechelmann8, A. Immenhauser8, D. K. Richter8, and A. Mangini1
1Heidelberg Academy of Sciences, Heidelberg, Germany
2Institute for Geosciences, University of Mainz, Mainz, Germany
3Institute for Geology and Palaeontology, University of Innsbruck, Innsbruck, Austria
4Institute for Geography, University of Mainz, Mainz, Germany
5Climate Risk Analysis, Hanover, Germany
6Institute for Geosciences, Goethe University Frankfurt, Frankfurt, Germany
7Department of Earth Sciences, Stellenbosch University, Private Bag X1, Matieland 7602, South Africa
8Institute for Geology, Mineralogy and Geophysics, Ruhr-University Bochum, Bochum, Germany

 Abstract. Holocene climate was characterised by variability on multi-centennial to multi-decadal time scales. In central Europe, these fluctuations were most pronounced during winter. Here we present a record of past winter climate variability for the last 10.8 ka based on four speleothems from Bunker Cave, western Germany. Due to its central European location, the cave site is particularly well suited to record changes in precipitation and temperature in response to changes in the North Atlantic realm. We present high-resolution records of δ18O, δ13C values and Mg/Ca ratios. Changes in the Mg/Ca ratio are attributed to past meteoric precipitation variability. The stable C isotope composition of the speleothems most likely reflects changes in vegetation and precipitation, and variations in the δ18O signal are interpreted as variations in meteoric precipitation and temperature. We found cold and dry periods between 8 and 7 ka, 6.5 and 5.5 ka, 4 and 3 ka as well as between 0.7 and 0.2 ka. The proxy signals in the Bunker Cave stalagmites compare well with other isotope records and, thus, seem representative for central European Holocene climate variability. The prominent 8.2 ka event and the Little Ice Age cold events are both recorded in the Bunker Cave record. However, these events show a contrasting relationship between climate and δ18O, which is explained by different causes underlying the two climate anomalies. Whereas the Little Ice Age is attributed to a pronounced negative phase of the North Atlantic Oscillation, the 8.2 ka event was triggered by cooler conditions in the North Atlantic due to a slowdown of the thermohaline circulation.

 Final Revised Paper (PDF, 2415 KB)   Discussion Paper (CPD)   Special Issue

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