Oxygen Isotopic Signatures of Major Climate Modes and Implications for Detectability in Speleothems

Abstract

Natural and social systems worldwide are impacted by climate modes such as the El Niño/Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO) and Atlantic Multidecadal Oscillation (AMO), making it imperative to understand their sensitivity to climate change. Paleoclimate studies extend the observational climate baseline, and speleothem records (δ18Ospel) are a common data source. However, relationships between δ18Ospel and climate modes are uncertain; climate models provide a way to test the strength and stability of these relationships. Here, we use the isotope-enabled Community Earth System Model's Last Millennium Ensemble combined with a forward proxy model to delineate the global expression of modal variability in “pseudo-stalagmite” (δ18Ospel) records worldwide. The modeled δ18Ospel spatially correlates with modal signatures. However, substantial changes in modal variance only modestly affect individual δ18Ospel variance. A network of δ18Ospel records, particularly one that straddles the Pacific, significantly improves the reconstructability of ENSO variance.