North Atlantic deep water circulation collapse during Heinrich events

Paleoceanographic proxy data and ocean general circulation models have been combined to investigate the response of the North Atlantic Ocean to Heinri ch-type meltwater episodes. Because of the uncertainties over the origin of the Heinrich events, three different scenarios have been modeled: (1) a He inrich event caused by a dramatic increase in the iceberg discharge from th e Laurentide ice sheet or Labrador ice shelf, (2) a Heinrich event driven b y enhanced iceberg discharge from the Barents shelf, which was transported into the northern North Atlantic, and (3) a meltwater episode that was conf irmed to the Nordic Seas. The ocean regional and global circulation models cannot distinguish between the Laurentide and Barents shelf Heinrich event scenarios because both led to a complete cessation of the deep-water thermo haline conveyor belt. The meltwater episode confined to the Nordic Seas onl y weakened the overturning and may represent circulation changes that may o ccur during the Dansgaard-Oeschger events.