The cause of a rapid change in Atlantic Ocean circulation and northern cooling at the onset of Heinrich Stadial 1 ~18.5 ka is unclear. Previous studies have simulated the event using ice sheet and/or iceberg meltwater forcing, but these idealized freshwater fluxes have been unrealistically large. Here we use a different approach, driving a high-resolution drainage network model with a recent time-resolved global paleo-ice sheet reconstruction to generate a realistic meltwater forcing. We input this flux to the Hadley Centre Coupled Model version 3 (HadCM3) climate model without adjusting the timing or amplitude and find that an acceleration in northern ice sheet melting (up to ~7.5 m/kyr global mean sea level rise equivalent) triggers a 20% reduction in the Atlantic Meridional Overturning Circulation. The simulated pattern of ocean circulation and climate change matches an array of paleoclimate and ocean circulation reconstructions for the onset of Heinrich Stadial 1, in terms of both rates and magnitude of change. This is achieved with a meltwater flux that matches constraints on sea level changes and ice sheet evolution around 19–18 ka. Since the rates of melting are similar to those projected for Greenland by 2200, constraining the melt rates and magnitude of climate change during Heinrich Stadial 1 would provide an important test of climate model sensitivity to future ice sheet melt.
Bibliographical noteFunding Information:
R. F. Ivanovic acknowledges support from NERC grant NE/K008536/1. Numerical climate model simulations made use of the N8 High Performance Computing (HPC) Centre of Excellence (N8 consortium and EPSRC grant EP/K000225/1) and ARC2, part of the HPC facilities at the University of Leeds, UK. L. F. Robinson and H. C. Ng acknowledge support from ERC grant 278705 and NERC grant NE/N003861/1. The contribution of J. F. McManus was supported in part by the U.S. NSF. J. Dentith was funded by NERC SPHERES Doctoral Training Partnership (NERC grant NE/L002574/1). Thanks are due to Kerry Callaghan for assistance in preparing the drainage basins. We are also grateful to the Editor, Stephen Barker, and to Samuel Toucanne and an anonymous reviewer for helpful comments that improved the manuscript. The new model data presented here are available from the University of Leeds Research Data repository: https://doi.org/10.5518/400. All climate and ocean circulation proxy data compared to are published elsewhere, as referenced. R. F. Ivanovic and L. J. Gregoire designed the study and analyzed the results. A. D. Wickert built and ran the drainage network model, with input from J. X. Mitrovica, to produce the meltwater fluxes. R. F. Ivanovic and L. J. Gregoire designed and performed the climate model experiments, based on a simulation designed and setup by P. J. Valdes, L. J. Gregoire, and R. F. Ivanovic. A. Burke obtained the surface climate proxy data and oversaw its comparison to the model results. H. C. Ng, L. F. Robinson, and J. F. McManus provided the 230Pa/231Th compilation. L. Lee contributed to the statistical analysis of the results. J. E. Dentith developed code used in the analysis. R. F. Ivanovic, L. J. Gregoire, A. Burke, and A. D. Wickert prepared the manuscript with input from all authors.
- Heinrich Stadial 1
- freshwater forcing