Changes in intensity and seasonality of Southern Westerlies in Subtropical Chile since the Late Pleistocene

MALDONADO, A.; DE PORRAS, M.E

Workshop; Workshop SHAPE and SWEEP; 2016

The high Andes from Subtropical Chile is a key area to study interaction between Subtropical Southeast Pacific High and the northern edge of the Southern Westerlies Wind Belt (SW) in the past since its location, the availability of proper palaeoclimatic archives and the low human disturbance. Here, the Interplay between both systems determines the current mediteranean-type climatecharacterized by rainy winters and dry summers, allowing to trace the winter activity of westerlies at millennial-to-interannual time scales. The present paper aims to show the dynamics of the northern edge of the SW during the last 15ka based on pollen records of high Andean lakes (30°-33°S).These records suggest cooler/wetter than present conditions during the Late Pleistocene followed by warm/humid conditions during early Holocene, which change to very dry conditions between 7-6ka and then gradually turned to more humid conditions at 2ka. These climatic trends show a high concordance with records of lowlands from Subtropical Chile, suggesting a regional climatic control related to the SW past dynamics. These inferences were discussed with records of temperate Chile (~40ºS), sensitive to summer rainfall. Opposite rainfall patterns between both areas during some periods could be explained by the variability of seasonality of the SW through time. Acknowledgements: FONDECYT#1140837