Mid-Holocene mean climate in the south eastern Pacific and its influence on South America

Abstract

The eastern tropical Pacific plays a key role in the tropical atmospheric circulation and in the global carbon cycle, and assessing the sensitivity of this region to global climate changes is a major challenge facing climatologists. Provided here is a synthesis of proxy records of the mean climate of the mid- Holocene (5e8 ka) along the south eastern Pacific margin and four regions of South America. These regions were selected for the strength and stability of ENSO teleconnections, and located outside the direct influence of the intertropical convergence zone or the southern westerlies in order to avoid the overprinting signal of their insolation-related variations and focus on the relationship between the eastern tropical Pacific and South America. This study is based on a review of published multiproxy data as well as new isotopic data from the Peruvian and Chilean coast. The available evidence indicates that sea-surface temperatures were w1e4 C cooler from the Galapagos to the southern Peruvian coast as a result of increased coastal upwelling forced by changes in longshore windfields. The mean La Niña-like conditions in the eastern South Pacific were associated to aridity in southern Brazil and along the whole South American Pacific coast from central Chile to the Galapagos, and to wetter conditions on the western central Andes. This regional synthesis provides a coherent picture of the South American mean climate that is very similar to the modern precipitation pattern observed during La Niña conditions, suggesting that atmospheric teleconnections linking the South Eastern Pacific to these continental areas were similar in the middle Holocene.