Ice-shelf collapse from subsurface warming as a trigger for Heinrich events, PNAS, Shaun A. Marcott et al.

Proceedings of the National Academy of Sciences, published online before print August 1, 2011; doi: 10.1073/pnas.1104772108

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

1. Shaun A. Marcott^a,¹, 
2. Peter U. Clark^a, 
3. Laurie Padman^b, 
4. Gary P. Klinkhammer^c, 
5. Scott R. Springer^d, 
6. Zhengyu Liu^e, 
7. Bette L. Otto-Bliesner^f, 
8. Anders E. Carlson^e,^g, 
9. Andy Ungerer^c, 
10. June Padman^c, 
11. Feng He^e, 
12. Jun Cheng^h, and 
13. Andreas Schmittner^c

Abstract

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.

http://www.pnas.org/content/early/2011/07/25/1104772108.abstract