Ice-shelf collapse from subsurface warming as a trigger for Heinrich events

• Published in: Proceedings of the National Academy of Sciences
• Main Authors: Marcott, Shaun A., Clark, Peter U., Padman, Laurie, Klinkhammer, Gary P., Springer, Scott R., Liu, Zhengyu, Otto-bliesner, Bette L., Carlson, Anders E., Ungerer, Andy, Padman, June, He, Feng, Cheng, Jun, Schmittner, Andreas
• Format: Article in Journal/Newspaper
• Language: English
• Published: Natl Acad Sciences 2011
• Subjects: paleoceanography; paleoclimatology; abrupt climate change; Hudson; Hudson Strait; Antarc*; Antarctica; Ice Sheet; Ice Shelf; Northwest Atlantic
• Online Access: https://archimer.ifremer.fr/doc/00227/33819/32479.pdf; https://archimer.ifremer.fr/doc/00227/33819/32480.pdf; https://doi.org/10.1073/pnas.1104772108; https://archimer.ifremer.fr/doc/00227/33819/

Episodic iceberg-discharge events from the Hudson Strait Ice Stream (HSIS) of the Laurentide Ice Sheet, referred to as Heinrich events, are commonly attributed to internal ice-sheet instabilities, but their systematic occurrence at the culmination of a large reduction in the Atlantic meridional overturning circulation (AMOC) indicates a climate control. We report Mg/Ca data on benthic foraminifera from an intermediate-depth site in the northwest Atlantic and results from a climate-model simulation that reveal basin-wide subsurface warming at the same time as large reductions in the AMOC, with temperature increasing by approximately 2 C over a 1-2 kyr interval prior to a Heinrich event. In simulations with an ocean model coupled to a thermodynamically active ice shelf, the increase in subsurface temperature increases basal melt rate under an ice shelf fronting the HSIS by a factor of approximately 6. By analogy with recent observations in Antarctica, the resulting ice-shelf loss and attendant HSIS acceleration would produce a Heinrich event.