Abstract
Abstract. This study presents results from a glacier-climate model that reconstructed glacio-climatological conditions during the last local glaciation maximum (LLGM) in the Cordillera to the north of Cochabamba (17°15'S, 66°15'W), Bolivia. Results emphasize the temperature-sensitivity of glaciers on the eastern slope of the Cordillera Oriental. Maximum glacier advances appear to have been caused by a massive cooling of about 6.5°C while annual preeipitation was about 300 mm higher than today (850 mm/yr). Modeling results indicate maximum glacial advances during cold phases such as MIS 2 (25–18 kyr B.P.) and minor advances during late glacial cool events (12–10 kyr B.P.). This chronology is supported by exposure age dating results. Further evidence may be found in the low AAR-values (accumulation area ratio) which indicate low mass balance gradients and therefore cold climate conditions. Modeled basal shear stresses smaller than 1 bar exelude extremely «cold-dry» or «warm-wet» conditions. The spatial pattern of regional paleo-ELA's (equilibrium line altitude). with higher ELAs in the western part of the study area, reflects a strong east-west gradient in paleoprecipitation. Easterly summer preeipitation is suggested to be the reason for this phenomenon. These results are in agreement with other studies of the east-Andean slope, indicating temperature as the driving factor for maximum glacier advances in northwestern Argentina.
Highlights
The Central Andes of South America (16°S-30°S) experienced major climatic changes during the late Quaternary, making this high altitude mountain region a key area for the study of processes and dynamics of tropical and extratropical climate variability
Provide quantifiable data for these environmental changes which occurred during the late Pleistocene and Holocene
Snow fields on the south face of Cerro Tunari, as seen on a field trip end of May 2005 indicate that a modern equilibrium line altidudes (ELA) would probably be not much higher than the highest peaks in the research area
Summary
The Central Andes of South America (16°S-30°S) experienced major climatic changes during the late Quaternary, making this high altitude mountain region a key area for the study of processes and dynamics of tropical and extratropical climate variability. The synthesis points to the climatic sensitivity of this region (Markgraf et al 2000).The challenge is to disentangle local and regional influences from hemispheric or global influences and processes of past climate variability (see Kull & Grosjean 1998). The derived spatial and chronological pattern of climate variability in the western cordillera of northern Chile shows dynamical links to the extra¬ tropical westerly circulation south of 27°S and to the tropical influence in the northern part (Kull et al.2002). There is still an ongoing debate about the chronology, the geographical extension and the related magnitude of late Pleistocene - Holocene environmental changes (Baker et al 2001; Mourguiard & Ledru 2003; Sylvestre et al 1999)
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