We thank D. Thornalley, R. Ji and Ø. Paasche for their feedback on early versions of the study, as well as H. Hátún, D. G. Boyce and D. Johns for contributing oceanographic and planktonic data shown in the study; M. Legrand for sharing the GRIP93a ice core [MSA] data; the students and staff of the DRI ice core group for assistance in the field and laboratory; the National Science Foundation (NSF) Ice Core Facility (formerly NICL), A. York, M. Bingham, M. Hatch and Milton Academy students for the Greenland Central (GC) ice core sampling, processing and [MSA] analysis support. Funding for retrieval and analysis of the GC ice core was provided by the US NSF Arctic System Science Program (award OPP-1205196 to S.B.D. and OPP-1205008 to M.J.E.). M.B.O. acknowledges support from the US Department of Defense Office of Naval Research – National Defense Science and Engineering Graduate (NDSEG) fellowship, and an Ocean Outlook Fellowship to the Bjerknes Centre for Climate Research. M.B.O. and S.B.D. further acknowledge institutional support from the Woods Hole Oceanographic Institution (WHOI). H.F. acknowledges support of the tracer glaciological work along the North Greenland Traverse (NGT) 1993–95 by the German Research Foundation (DFG) and the long-term support of ice core science at the University of Bern by the Swiss National Science Foundation (SNF). Collection and analysis of the D4, TUNU and Summit2010 cores were supported by NSF grants 0221515, 0909541 and 1204176 to J.R.M. E.S.S. acknowledges NASA grant NNX15AF31G.

Reviewer information

Nature thanks John Dunne, Rafel Simo and the other anonymous reviewer(s) for their contribution to the peer review of this work.