Relationships between southern Chilean varved lake sediments,precipitation and ENSO for the last 600 years |
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| Authors: | Xavier Boës Nathalie Fagel |
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| Institution: | (1) Clays and Paleoclimate Research Unit, University of Liège, 4000 Liege, Belgium |
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| Abstract: | In this paper, the relationships between paleo-precipitation and the regional influence of El Nino Southern Oscillation (ENSO)
in South America are assessed from a high-resolution calendar varve-thickness record. Two short laminated sediment cores (53
and 61 cm length) from Lago Puyehue (40° S) are analysed by continuous varve measurements through the last 600 years. The
calendar varve years are determined by the occurrence of graded planktonic-rich layers. The annual sediment accumulation rates
are reconstructed by using the standard varve-counting methods on thin sections. The 1980–2000 varve-thickness record is interpreted
in terms of climate through correlation with limnological and local monthly instrumental climate databases. The comparison
between the standardized varve thickness with the instrumental records reveals a strong correlation (r = 0.75, р = 0.07) between the total varve thickness and the austral autumn/winter precipitation. We argue that strong austral winter
winds and precipitation are the forcing factors for the seasonal turn-over and phytoplankton increase in the lake sediments.
During strong El Nino events the precipitation and the winds decrease abnormally, hence reducing the thickness of the biogenic
sediments deposited after the winter turn-over. Our results show one significant regional maximum peak of winter precipitation
(>900 mm) in the mid 20th century and a significant period with lower winter precipitation (<400 mm) before the 15th century,
i.e., the late Medieval Warm Period. The first peak in the mid 20th century is confirmed by the regional precipitation database.
The influence of ENSO cycles over the last 600 years is assessed by spectral analysis in Fagel et al. (2007). The possible influence of the regional volcanism and/or the seismic activity on the local climate record is also discussed.
This is the sixth in a series of eight papers published in this special issue dedicated to the 17,900 year multi-proxy lacustrine record of
Lago Puyehue, Chilean Lake District. The papers in this special issue were collected by M. De Batist, N. Fagel, M. -F. Loutre
and E. Chapron. |
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| Keywords: | Chile Lake District Varve counting Varves ENSO Late Medieval Warm Period Last millennium |
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