Long-term quantitative climate reconstructions in south-central Chile (37-40°S)

ABARZUA A M; TONELLO M S; GONZALEZ A

Salvador, Bahía

Congreso; XIV International Palynologicall Congress; 2016

The climatic transition between 38-40°S in south central Chile, present an excellent possibility to evaluate different Southern Westerly Winds patterns/movement observed from sedimentological and vegetation changes. Many paleoclimatic proxy records suggest that the Holocene climate of southern South America was highly variable, especially during the mid- and late Holocene. However, for the Last Glacial Maximun period, very few records are focused on this time window being the detail and its climate variability and quantitative magnitudes rather unknown. Here we present a preliminary quantitative climate reconstruction applied in the Lago Espejo pollen record using a modern regional pollen calibration data set and non-linear unimodal-based reconstruction techniques, such as weighted-averaging regression. The calibration set consists of 40 sites distributed over different regional vegetational units, which roughly encompasses the temperate rainforests, deciduous forests, evergreen forests and high Andean forests with conifers. Pollen records from different depositional environments: lakes, swamps and mosses, which were analyzed under standard procedures and recorded approximately 100 pollen taxa. Climatic variables precipitation and temperature were obtained from records of meteorological stations and correspond to normal climate period between 1980 - 2015. The relationship of the different pollen types registered with climatic variables selected as the basis for the construction and subsequent evaluation of different models of quantitative climate reconstruction is presented.The 26,000 cal yr BP time window addressed by the high resolution Lago Espejo pollen record have the opportunity to quantify in detail the climatic trends and biogeographical patterns at the west side of the Andes. The preliminary reconstructed precipitation values suggest hiper-humid conditions during the LGM until 17,000 cal yr BP, when becomes dryer and warmer as today. Pleistocene?Holocene transition (12,500?10,500 cal yr BP) is marked by high fire activity under cold conditions. Precipitation was low from 10,500 to 7000 cal yr BP and increased between 7000 and 2300 cal yr BP. These results will allow deepening our understanding concerning timing, quantitative magnitudes, and directions of climate variations and disturbance regimes during the Last Glacial period and the Holocene in south-central Chile, and their relationship with regional, inter-hemispheric, and global climate trends.