Environmental and climatic changes in central Chilean Patagonia since the Late Glacial (Mallín El Embudo, 44° S)

F A Quintana,A Maldonado,M E De Porras,A Martel-Cea,C Méndez,O Reyes

doi:10.5194/cp-10-1063-2014

Abstract

Abstract. Multi-millennial environmental and climatic changes in central Chilean Patagonia (44–49° S) during the Last Glacial–Interglacial cycle have been of particular interest as changes in the position and strength of the southern westerlies are the major forcing factor conditioning the environmental dynamics. Recent attempts to reconstruct regional environmental and climatic signals from central Chilean Patagonia reveal some discrepancies and unclear issues among the records. This paper presents the 13 ka pollen and charcoal records from Mallín El Embudo (44° 40' S, 71° 42' W) located in the deciduous Nothofagus forest in the middle Río Cisnes valley. The paper aims to (1) establish the timing and magnitude of local vegetation changes and fire activity since the Late Glacial and (2) integrate these results at the regional scale in order to discuss the discrepancies and depict the environmental and climatic dynamics in central Chilean Patagonia since the Late Glacial. Open landscapes dominated by grasses associated with scattered Nothofagus forest patches dominated the middle Río Cisnes valley between 13 and 11.2 ka suggesting low effective moisture but also indicating that landscape configuration after glacial retreat was still ongoing. At 11.2 ka, the sudden development of an open and quite dynamic Nothofagus forest probably associated with the synchronous high fire activity occurred, suggesting a rise in effective moisture associated with dry summers. Since 9.5 ka, the record reflects the presence of a closed Nothofagus forest related to higher effective moisture conditions than before combined with moderate dry summers that may have triggered a high frequency of low-magnitude crown fires that did not severely affect the forest. The forest experienced a slight canopy opening after 5.7 ka, probably due to slightly drier conditions than before followed by a sudden change to open forest conditions around 4.2 ka associated with fire and volcanic disturbances. Around 2 ka, the recovery of a closed Nothofagus forest related to slightly wetter conditions (similar to present) occurred and persisted under highly variable climatic conditions up to 0.1 ka when massive forest burning and logging due to European settlements occurred. Central Chilean Patagonian climatic and environmental changes at millennial–centennial timescales since the Late Glacial were driven by changes in the southern westerlies latitudinal position and/or intensity, but during the late Holocene fire, volcanism and humans arose as forces contributing to environmental dynamics.

Highlights

Past environmental and climatic variability of Patagonia (40–55◦ S) since the Late Glacial has been a major research topic because changes in the position and strength of the southern westerlies (SWs) are the major forcing factorPublished by Copernicus Publications on behalf of the European Geosciences Union.M
This paper presents the 13 ka pollen and charcoal records from Mallín El Embudo (44◦40 S, 71◦42 W) located in the Río Cisnes valley in order to establish the timing and magnitude of changes of the local vegetation and fire regime since the Late Glacial
The composite core consists of grey clays (817–844 cm) related to an ice-dammed lake, gyttja (813–817 cm) associated with organic lacustrine sedimentation and peat from 813 cm to the top of the core associated with the development of a mallín

Summary

Introduction

Past environmental and climatic variability of Patagonia (40–55◦ S) since the Late Glacial has been a major research topic because changes in the position and strength of the southern westerlies (SWs) are the major forcing factor. Patagonian records indicate that during the Last Glacial Maximum (∼ 21 ka; thousand calendar years before present), the SW core was shifted equatorward of its modern position, centered on 41◦ S (e.g., Villagrán, 1990; Moreno et al, 1999). After 5 ka, a breakdown of this symmetry occurred, implying that changes in the strength and latitudinal position of the southern westerlies were modulated at seasonal to interannual timescales by large-scale climate phenomena such as El Niño–Southern Oscillation and/or Southern Annular Mode (Fletcher and Moreno, 2011)

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