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; Older Dryas; saddle collapse; Ice Sheet
• Online Access: https://hdl.handle.net/1983/1ed85e73-c9ae-453d-a64f-254e8da47820; https://research-information.bris.ac.uk/en/publications/1ed85e73-c9ae-453d-a64f-254e8da47820; https://doi.org/10.1002/2016GL071849; https://research-information.bris.ac.uk/ws/files/111430739/Full_text_PDF_final_published_version_.pdf; https://research-information.bris.ac.uk/ws/files/113236299/grl55384_sup_0001_SI.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 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.