Abstract
Abstract. In this paper we explore a speleothem δ18O record from Palestina cave, northwestern Peru, at a site on the eastern side of the Andes cordillera, in the upper Amazon Basin. The δ18O record is interpreted as a proxy for South American Summer Monsoon (SASM) intensity and allows the reconstruction of its variability during the last 1600 years. Two periods of anomalous changes in the climate mean state corresponding to the Medieval Climate Anomaly (MCA) and the Little Ice Age (LIA) periods identified in the Northern Hemisphere are recognized in the record, in which decreased and increased SASM activity, respectively, have been documented. Variations in SASM activity between the MCA and the LIA seem to be larger over the northern part of the continent, suggesting a latitudinal dependence of the MCA footprint. Our results, based on time series, composite and wavelet analyses, suggest that the Atlantic Multidecadal Oscillation (AMO) plays an relevant role for SASM modulation on multidecadal scales (∼65 years), especially during dry periods such as the MCA. Composite analyses, applied to evaluate the influence of the AMO on the Palestina cave δ18O and other δ18O-derived SASM reconstructions, allow insight into the spatial footprints of the AMO over tropical South America and highlight differences between records during key studied periods. This work also reveals that replicating regional climate signals from different sites, and using different proxies is absolutely essential for a comprehensive understanding of past changes in SASM activity.
Highlights
South American paleoclimate reconstructions over the last millennium based on δ18O from different proxies such as speleothems, lake sediments and ice cores have shown regionally coherent patterns of change during distinct events recognized as the Medieval Climate Anomaly (MCA; AD 900–1250) and the Little Ice Age (LIA; AD 1400–1850)
The local meteorological water line (LMWL) obtained from 40 values of δ18O and δD pairs from each rainfall sampled nearby Palestina cave has a slope of ∼ 8.2, which is very close to the global meteorological water line (GMWL; Rozanski et al, 1992; Fig. S3 in the Supplement)
South American Summer Monsoon (SASM) activity exhibited departures from the mean state, which are relatively synchronous with major periods of global climate change, recognized as MCA and LIA
Summary
Reuter et al, 2009; Jomelli et al, 2009; Bird et al, 2011a; Vuille et al, 2012; Novello et al, 2012; Kanner et al, 2013) These climate anomalies are primarily manifested as changes in temperature over Northern Hemisphere oceanic and continental areas but appear more strongly related to variations in hydroclimatic conditions over tropical South America (e.g., Bird et al, 2011a; Vuille et al, 2012). A relatively dry climate is documented during the MCA over the Andes and in NE Brazil, while southern Brazil speleothems do not clearly document this dry period
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