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

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.

DOI: 10.1073/pnas.1104772108

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@article{Marcott2011IceshelfCF, title={Ice-shelf collapse from subsurface warming as a trigger for Heinrich events.}, author={Shaun A. Marcott and Peter U . Clark and Laurie Padman and Gary P. Klinkhammer and Scott R. Springer and Zhengyu Liu and Bette L. Otto-Bliesner and Anders E . Carlson and Andy Ungerer and June Padman and Feng He and Jun Cheng and Andreas Schmittner}, journal={Proceedings of the National Academy of Sciences of the United States of America}, year={2011}, volume={108 33}, pages={13415-9} }