title: 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.
authors.affiliation: Department of Geosciences, Oregon State University, Corvallis, OR 97331, USA. marcotts@geo.oregonstate.edu
authors.forename: Shaun A
authors.initials: SA
authors.lastname: Marcott
authors.forename: Peter U
authors.initials: PU
authors.lastname: Clark
authors.forename: Laurie
authors.initials: L
authors.lastname: Padman
authors.forename: Gary P
authors.initials: GP
authors.lastname: Klinkhammer
authors.forename: Scott R
authors.initials: SR
authors.lastname: Springer
authors.forename: Zhengyu
authors.initials: Z
authors.lastname: Liu
authors.forename: Bette L
authors.initials: BL
authors.lastname: Otto-Bliesner
authors.forename: Anders E
authors.initials: AE
authors.lastname: Carlson
authors.forename: Andy
authors.initials: A
authors.lastname: Ungerer
authors.forename: June
authors.initials: J
authors.lastname: Padman
authors.forename: Feng
authors.initials: F
authors.lastname: He
authors.forename: Jun
authors.initials: J
authors.lastname: Cheng
authors.forename: Andreas
authors.initials: A
authors.lastname: Schmittner
mesh_terms: D002118:Calcium / Q000032:analysis; D002980:Climate; D056908:Foraminifera / Q000737:chemistry; D017752:Greenhouse Effect; D046448:Ice Cover / Q000737:chemistry; D008274:Magnesium / Q000032:analysis; D009792:Oceans and Seas; D013696:Temperature; D014872:Water Movements
chemical_list: D008274:Magnesium; D002118:Calcium