Heinrich events have been attributed to surging of the Laurentide ice sheet every 7 thousand years or so during glacial time. These massive ice-rafting events only occurred during cold phases of millennial-scale, Dansgaard-Oeschger climate cycles. Other observed ice-rafting events, sourced from ice streams at various locations around the northern North Atlantic, occurred during all Dansgaard-Oeschger cold phases and led Heinrich events when the latter took place. Here it is suggested that ocean subsurface warming in the northern North Atlantic during the cold phases may provide the key to explaining these climate - ice rafting phasings. Such warming would lead to ice shelf melting and breakup. Without buttressing by ice shelves, ice streams may surge, leading to increased iceberg production. This interpretation is supported by results of a simplified, coupled climate model and by available sediment and ice sheet data.