Rapid climatic shifts during isotope stages 2–4 in the Polar North Atlantic

Abstract

Sediment cores from the Polar North Atlantic provide evidence of six periods 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 foraminifera/g; they last from 2000 to >10000 yr, and constitute ≈ 50% of the total time span. These periods of sea-ice breakup correlate temporarily to the Heinrich events and the early temperature maximum in the Bond cycles of the North Atlantic and Greenland ice record. Our hypothesis is that massive iceberg discharges that flooded the North Atlantic during each Heinrich event probably triggered an oceanographic regime that gave a much more vigorous surface circulation pattern in the Polar North Atlantic, which contributed to the breakup of the sea-ice cover. Open-water conditions in the Polar North Atlantic are inversely related to terrestrial interstadials of coastal Norway, suggesting ice-sheet starvation during the cold periods and ice-sheet growth when an open-water surface circulation existed in the Polar North Atlantic. Our data document synchronous variations on a October 1900 yr time scale between Arctic oceanic climate, Northern Hemisphere ice-sheet dynamics, and ocean-atmosphere temperature changes.