Southern westerlies during the Holocene deduced from geomorphological and pedological studies in the Norte Chico, northern Chile (27-33 degrees S)

In the Norte Chico precipitation is controlled by atmospheric perturbations and frontal systems associated with the belt of westerly wind circulation. The Holocene climatic history of the region can be reconstructed from geomorphic and pedologic investigations. In comparison to modern climatic conditions, increased influence of the westerlies is deduced for the time periods prior to 7300 yr B.P., between 5000-3700 yr B.P., 3000-1800 yr B.P. and around 270 yr B.P. It remains uncertain whether the increased influence of the westerlies was the consequence of northward shifts of the westerlies as a whole, of a meridional expansion of the westerly belt, or only of intensity changes of the atmospheric dynamics. Almost synchronous with changes in the westerlies the coastal fogs in the region were apparently reduced or the fog belt in the coastal range was elevated, probably due to a weakened upwelling and warmer water conditions in the eastern Pacific. In general, the climate of the Norte Chico has become more variable since 5000 yr B.P., especially since 3000 yr B.P., with frequent changes of the geoecological conditions.