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 Nina; to the south precipitation originates from the Pacific Ocean, dominated by winter storm events linked to El Nino. 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 Nino 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.

Automated summary

The non-stationary nature of the Andean Dry Diagonal (ADD) and the varying 'flavours' of El Nino phenomenon associated with it may explain the contradictory interpretations in reconstructing past climates of the Atacama Desert. The ADD's position is not stable over seasonal and longer periods, leading to potential displacement, intensification or weakening of climates in the region. Understanding the spatial distinctiveness of El Nino and its association with the mobile ADD could provide a more sophisticated approach to paleoclimate research and resolve some difficulties.