The Little Ice Age in Southern South America: Proxy and Model Based Evidence

Abstract

In this chapter climatic changes over southern South America during the last millennium with focus on the period of the Little Ice Age (LIA 1550–1800 AD) are investigated. Results presented are based on proxy and modelling evidence. Proxy studies include a variety of different sites, ranging from geomorphological, lacustrine, pollen to tree ring reconstructions. These different sources of evidence are combined into a multi-proxy network. Based on this network, spatio-temporal climatic changes in southern South America are assessed for the last millennium. A climate model simulation of the last millennium is used to investigate the influence of external forcing parameters, such as solar, volcanic and greenhouse gases on the local climate in southern South America. To compare proxy-based results and the output of the global climate model on a common basis, conceptual and quantitative downscaling and upscaling models are established. Based on these methodological approaches both reconstruction methods indicate a period of wetter conditions in south-eastern South America during the period of the LIA. Investigating the driving mechanisms for hydrological changes during the LIA, large-scale atmospheric circulation changes of the Southern Hemispheric Westerlies (SHWs) over southern South America are indicated in modelling results. Changes of the SHWs during the LIA also fit into the spatial pattern indicated by different proxies with wetter conditions and cooler temperatures in south-eastern South America accompanied with drier and warmer conditions to the north.