Collapse of the North American ice saddle 14,500 years ago caused widespread cooling and reduced ocean overturning circulation

Ruza F. Ivanovic, Lauren J. Gregoire, Andrew D. Wickert, Paul J. Valdes, Andrea Burke

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18 Scopus citations


Collapse of ice sheets can cause significant sea level rise and widespread climate change. We examine the climatic response to meltwater generated by the collapse of the Cordilleran-Laurentide ice saddle (North America) ~14.5 thousand years ago (ka) using a high-resolution drainage model coupled to an ocean-atmosphere-vegetation general circulation model. Equivalent to 7.26 m global mean sea level rise in 340 years, the meltwater caused a 6 sverdrup weakening of Atlantic Meridional Overturning Circulation (AMOC) and widespread Northern Hemisphere cooling of 1–5°C. The greatest cooling is in the Atlantic sector high latitudes during Boreal winter (by 5–10°C), but there is also strong summer warming of 1–3°C over eastern North America. Following recent suggestions that the saddle collapse was triggered by the Bølling warming event at ~14.7–14.5 ka, we conclude that this robust submillennial mechanism may have initiated the end of the warming and/or the Older Dryas cooling through a forced AMOC weakening.

Original languageEnglish (US)
Pages (from-to)383-392
Number of pages10
JournalGeophysical Research Letters
Issue number1
StatePublished - Jan 16 2017

Bibliographical note

Funding Information:
R.F.I. is funded by Natural Environment Research Council (NERC) grant NE/K008536/1. Numerical climate model simulations made use of the N8 HPC Centre of Excellence (N8 consortium and EPSRC grant EP/K000225/1). We are grateful to Piers Forster and two anonymous reviewers for helpful comments and to Kim Cobb for swift editorial handling. Presented model data are available upon request, please e-mail


  • AMOC
  • Older Dryas
  • ice sheet melt
  • saddle collapse

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