RAPID CLIMATIC SHIFTS DURING ISOTOPE STAGES-2-4 IN THE POLAR NORTH-ATLANTIC

Sediment cores from the Polar North Atlantic provide evidence of six p eriods of sea-ice breakup during isotope stages 4, 3, and 2, probably caused by inflow of North Atlantic surface water into the Polar North Atlantic, These periods are characterized by having a high number of f oraminifera/g; they last from 2000 to > 10 000 yr, and constitute simi lar to 50% of the total time span. These periods of sea-ice breakup co rrelate temporarily to the Heinrich events and the early temperature m aximum in the Bond cycles of the North Atlantic and Greenland ice reco rd, Our hypothesis is that massive iceberg discharges that flooded the North Atlantic during each Heinrich event probably triggered an ocean ographic regime that gave a much more vigorous surface circulation pat tern in the Polar North Atlantic, which contributed to the breakup of the sea-ice cover, Open-water conditions in the Polar North Atlantic a re inversely related to terrestrial interstadials of coastal Norway, s uggesting ice-sheet starvation during the cold periods and ice-sheet g rowth when an open-water surface circulation existed in the Polar Nort h Atlantic, Our data document synchronous variations on a 1000 yr time scale between Arctic oceanic climate, Northern Hemisphere ice-sheet d ynamics, and ocean-atmosphere temperature changes.