A Global Speleothem-Based Assessment of Spontaneous Dansgaard–Oeschger Type Oscillations in Two Isotope-Enabled General Circulation Models

Several general circulation models have now demonstrated the ability to simulate spontaneous millennial-scale oscillations that resemble Dansgaard–Oeschger (DO) events. It is often unclear how representative of DO events these simulations are, particularly outside of the polar regions. To test this, we directly compare simulated changes from two isotope-enabled models to a compilation of 111 speleothem records from 67 caves across the low- and mid-latitudes. We find that both models successfully reproduce the observed pattern of changes in Europe and the Mediterranean, Asia, and Central America. However, they perform less well for Western North America, South America, and Oceania, and the simulated changes are also generally too small in their magnitude. Where the models do reproduce the observed changes, we find evidence that the isotopic variability is influenced by both local and remote drivers, but the remote drivers appear more important.