Acceleration of northern ice sheet melt induces AMOC slowdown and northern cooling in simulations of the early last deglaciation

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 639 ERC grant 278705 and NERC grant NE/N003861/1. The contribution of J.F. McManus was supported in part by the US NSF. J. Dentith was funded by NERC SPHERES Doctoral Training 641 Partnership (NERC grant NE/L002574/1).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 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‐1 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 palaeoclimate and ocean circulation reconstructions for the onset of Heinrich Stadial 1, both in terms of 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.Publisher PDFPeer reviewe