Dynamic Earth System Response to Interacting Climate Forcing Factors Through the Penultimate Deglaciation and Last Interglacial

Abstract The Penultimate Deglaciation (PDG) saw warming from the Penultimate Glacial Maximum to the Last Interglacial (LIG). We present 18‐kyr transient simulations through the PDG into the LIG using a fully‐coupled three‐dimensional ocean‐atmosphere model forced with Paleoclimate Modeling Intercomparison Project Phase 4 transient boundary conditions. We perform sensitivity experiments to disentangle the roles of the multiple drivers. We also perform steady‐state simulations with matched boundary conditions to explore Earth‐system memory. We focus on time series of global temperature, Atlantic Meridional Overturning Circulation (AMOC) strength and Asian monsoon precipitation. Our simulations are suggestive of a tight coupling of these Earth‐system components, with meltwater‐driven AMOC variability driving the timing of changes in global temperature and Asian monsoon strength. The magnitude of glacial‐interglacial warming is dominated by CO 2 and ice sheets, but the timing is highly sensitive to orbital forcing and meltwater fluxes. Transient and steady‐state global temperatures can differ by up to 2.0°C during the deglaciation. Relative to steady state, transient simulations find delayed multi‐millennial global warming, a marginally cooler early LIG, and differences in AMOC hysteresis. The 127 ka timeslice is more sensitive to disequilibrium effects compared to later stages of the LIG. The occurrence of an interstadial in the early PDG depends on the profile of meltwater forcing. Timing of final AMOC recovery is accelerated by ice‐sheet retreat and precession. Indian monsoon strengthening is primarily driven by precession and CO 2 , but the timing is linked to AMOC recovery. Indian Monsoon variability is qualitatively most closely simulated using the meltwater forcing profile derived from ice‐rafted debris.