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

• Published in: Proceedings of the National Academy of Sciences
• Other Authors: Marcott, Shaun (author), Clark, Peter (author), Padman, Laurie (author), Klinkhammer, Gary (author), Springer, Scott (author), Liu, Zhengyu (author), Otto-Bliesner, Bette (author), Carlson, Anders (author), Ungerer, Andy (author), Padman, June (author), He, Feng (author), Cheng, Jun (author), Schmitttner, Andreas (author)
• Format: Article in Journal/Newspaper
• Language: English
• Published: National Academies Press 2011
• Subjects: Paleoceanography; Paleoclimatology; Abrupt climate change; Hudson; Hudson Strait; Antarc*; Antarctica; Ice Sheet; Ice Shelf; Northwest Atlantic
• Online Access: http://nldr.library.ucar.edu/repository/collections/OSGC-000-000-003-853; https://doi.org/10.1073/pnas.1104772108

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.