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

• Published in: Geophysical Research Letters
• Main Authors: Ivanovic, Ruza F., Gregoire, Lauren J., Wickert, Andrew D., Valdes, Paul J., Burke, Andrea
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2017
• Subjects: AMOC; Ice sheet melt; Saddle collapse; Older Dryas; Ice Sheet
• Online Access: https://research-portal.st-andrews.ac.uk/en/researchoutput/collapse-of-the-north-american-ice-saddle-14500-years-ago-caused-widespread-cooling-and-reduced-ocean-overturning-circulation(1cca33c6-6e5b-42ea-ab50-b9026e5067c6).html; https://doi.org/10.1002/2016GL071849; https://research-repository.st-andrews.ac.uk/bitstream/10023/10076/1/Ivanovic_et_al_2017_Geophysical_Research_Letters.pdf

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 ~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.