The effect of an ice shelf in the Labrador Sea on ice-rafted sediment delivery to the glacial North Atlantic is investigated using a finite element numerical model of ice shelf flow. Discharge into the shelf from Hudson Strait creates a thick central core, extending downstream into the shelf, that is flanked by relatively thin ice. Melting at the base of the deep keel would produce cool, fresh water which would rise to refreeze along the keel's flanks. Debris deposited by melting deep central ice could create the Heinrich layers observed in the Labrador Sea while the debris-rich ice protected by basal freezing on the flanks of the thick ice plume could transport sediment over large distances. Heinrich layers would be produced solely by external climate forcing, without changes in ice sheet flow. The mechanism is plausible if the lifetime of the ice shelf is about 1000 years.