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

Natural and social systems worldwide are impacted by climate modes such as the El Nino/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 (delta O-18(spel)) are a common data source. However, relationships between delta O-18(spel) 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 (delta O-18(spel)) records worldwide. The modeled delta O-18(spel) spatially correlates with modal signatures. However, substantial changes in modal variance only modestly affect individual delta O-18(spel) variance. A network of delta O-18(spel) records, particularly one that straddles the Pacific, significantly improves the reconstructability of ENSO variance.

Automated summary

This study uses a model to investigate the global expression of modal variability in stalagmite records and finds that there is spatial correlation between δO-18(spel) and modal signatures. However, significant changes in modal variance only have a modest effect on individual δO-18(spel) variance. In particular, a network of stalagmite records spanning the Pacific significantly enhances the reconstructability of ENSO variance.