ASSESSING THE POTENTIAL OF OXYGEN ISOTOPES IN ARCHAEOLOGICAL SHELL MIDDENS IN NORTHERN CHILE TO RECONSTRUCT HOLOCENE ENSO VARIABILITY

Changes in ocean and atmospheric circulation associated with ENSO variability have large impacts on human society. Understanding how ENSO, and the mean state of ENSO, has changed spatially and temporally over the Holocene is key for constraining models that predict ENSO response to future climate change. Here we assess the potential of using ontogenetic oxygen isotope analyses for a variety of shells (Concholepas concholepas, Mytilus chilensis, Siliqua patula) found in archaeological shell middens in Caleta Camarones, northern Chile, throughout the Holocene, to reconstruct past ENSO variability. Similar analyses of oxygen isotopes of marine shells in archaeological shell middens in southern Peru have provided a wealth of information on past ENSO behavior. This study aims to expand the spatial extent of ENSO reconstruction down the Pacific coast. We also analyzed a variety of modern shells collected in July of 2016. The recent 2015-2016 El Niño event was the first El Niño since the 1997-1998 event to cause significant changes in sea surface temperatures along the coast of northern Chile. As such, evidence of this event in the modern samples is necessary for assessing the potential of shell midden material to provide information on past ENSO variability. Shell midden sclerochronology has provided a wealth of information on past climate and environmental change. However, calibration of the modern system is essential for properly characterizing past climate variability. This research represents a cautious first step in assessing the potential of archaeological shell middens in northern Chile to reconstruct past ENSO variability, based on primary result of analyses of modern and archaeological shells.