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A quantitative high-resolution summer temperature reconstruction based on sedimentary pigments from Laguna Aculeo, central Chile, back to AD 850

University of Bern, Oeschger Centre for Climate Change Research & Institute of Geography, Erlachstrasse 9a, 3012 Bern, Switzerland, lucien.vongunten{at}giub.unibe.ch

Martin Grosjean

University of Bern, Oeschger Centre for Climate Change Research & Institute of Geography, Erlachstrasse 9a, 3012 Bern, Switzerland, University of Bern, NCCR Climate, Erlachstrasse 9a, 3012 Bern, Switzerland

Bert Rein

University of Mainz, Institute for Geosciences, Becherweg 21, Mainz 55099, Germany, GeoConsult Rein, Katharinenblick 5, Oppenheim 55276, Germany

Roberto Urrutia

Universidad de Concepción, Centro EULA-Chile, Concepción, Chile

Peter Appleby

Department of Mathematical Sciences, University of Liverpool, Liverpool L69 3BX, UK

We present a pigment-based quantitative high-resolution (five years) austral summer DJF (December to February) temperature reconstruction for Central Chile back to AD 850. We used non-destructive in situ multichannel reflection spectrometry data from a short sediment core of Laguna Aculeo (33°50'S/70°54'W, 355 m a.s.l., central Chile). Calibration-in-time (period AD 1901—2000, cross-validated with split periods) revealed robust correlations between local DJF temperatures and total sedimentary chlorin (relative absorption band depth (RABD) centred in 660—670 nm RABD_660;670: r=0.79, P<0.01; five-years triangular filtered) and the degree of pigment diagenesis (R_{660nm/670 nm}: r=0.82, P<0.01; five-years triangular filter). Root Mean Squared Error values are small (between 0.24 and 0.34°C) suggesting that most of the reconstructed decadal-scale climate variability is significant. Our data provide quantitative evidence for the presence of a Medieval Climate Anomaly (in this case, warm summers between AD 1150 and 1350; T = +0.27 to +0.37°C with respect to (wrt) twentieth century) and a very cool period synchronous to the ‘Little Ice Age’ starting with a sharp drop between AD 1350 and AD 1400 (–0.3°C/10 yr, decadal trend) followed by constantly cool (T = –0.70 to –0.90°C wrt twentieth century) summers until AD 1750. The structure of variability is consistent in great detail with annually resolved tree-ring based warm-season temperature and river discharge reconstructions from northern Patagonia (42°S) for the past 400 years, with qualitative climate reconstructions from Andean glacier fluctuations, and with hydrological changes in Patagonian lake sediment records.

Key Words: Climate change • lake sediments • geochemistry • reflectance spectrometry • ‘Little Ice Age’ • South America.

The Holocene, Vol. 19, No. 6, 873-881 (2009)
DOI: 10.1177/0959683609336573


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