Heinrich event 1 (H1) is a climate event resulting from the release into the North Atlantic of a huge volume of sea ice and icebergs from the northern hemisphere ice sheets. We present here high-resolution diatom records from the Bermuda Rise (Sargasso Sea) and the Laurentian Fan (South of Newfoundland) to assess its impacts on North Atlantic surface circulation and its timing. The event is composed of three phases: the two first correspond to major pulses of Ice Rafted Debris (IRD) and the third phase relates to its immediate aftermath. At both sites, diatom abundances start to rise at 16.8 ka. This increase is marked by diatom species thriving in cold environments over the Laurentian Fan, while brackish and fresh water diatom species characterize this increase over the Bermuda Rise. This last record implies icebergs migration to subtropical latitudes and nutrient-rich meltwater to support such diatom productivity. During the second phase of the event, both sites record maximum diatom abundances, when sea ice conditions are dominant over the Laurentian Fan and the contribution of brackish-fresh water diatoms culminates over the Bermuda Rise. The persistence of lower salinity related diatom species over the Bermuda Rise suggests a continuous injection of cold fresh water by cold-core rings, as observed nowadays. The last phase witnesses the persistence of low salinity water over the Laurentian Fan, while a decrease towards the disappearance of diatoms in the sediment occurs over the Bermuda Rise. Regarding the relationship between IRD and diatom abundance, it appears that a critical amount of icebergs is necessary to stimulate diatom productivity. The disturbances induced by H1 appear to end ~14.6 ka over the Bermuda Rise, while over the Laurentian Fan, the high diatom production persists until 14.1 ka and the salinity anomaly until 13.8 ka.