Heinrich event

A Heinrich event is one of the events which occurred during the coldest point of "Bond Cycles" in which many icebergs were discharged into the North Atlantic and melted.
Evidence for this can be found in the north Atlantic sediment cores which show poorly sorted, angular and contain rocks. These were originally in the icebergs but dropped to the bottom of the ocean when the icebergs melted.
Heinrich events are a possible trigger to the onset of mini ice ages which follow a long period of thaw. An example might be the Younger Dryas, a brief cold period from about 12.8 thousand years ago to about 11.5 thousand years ago. 
The Younger Dryas stadial is thought to have been caused by the collapse of the North American ice sheets, although rival theories have been proposed.