The role of the non‐stationary Andean Dry Diagonal in paleoclimate reconstructions

Natural archives used to reconstruct past climates of the Atacama Desert sometimes lead to contradictory interpretations. One explanation for such contradictions is the non‐stationary nature of the Andean Dry Diagonal (ADD), a narrow zone of precipitation minima between two large scale weather systems. The ADD bisects the Central Andes; to the north precipitation originates from the Atlantic Ocean via Amazonia, largely in summer, with extreme events linked to La Niña; to the south precipitation originates from the Pacific Ocean, dominated by winter storm events linked to El Niño. The dynamic nature of these weather systems implies that the position of the ADD is not stable over seasonal and longer periods. Climates currently found either north or south of the ADD may in the past have been displaced, intensified or weakened leading to changes in the position of the ADD. For example, along the coastal regions of Peru and Chile, El Niño currently modulates both winter and summer precipitation. Flood episodes caused by these precipitation events are manifested in sedimentary and other natural archives that have been used to reconstruct past climates, yet have at times, produced contradictory interpretations. The realization that ENSO has varying ‘flavours’ that are spatially distinct and associated with a mobile ADD may allow a more sophisticated approach to paleoclimate research that has the potential to resolve some of these difficulties. Paleoclimate reconstructions may have viable alternative interpretations. In N Chile different weather systems exist N and S of the Andean Dry Diagonal (ADD). ADD displacement occurs due to changes in weather systems and their forcing mechanisms. Paleoclimate proxies may be influenced by multiple weather systems that need consideration.