Correlations between climate records from North Atlantic sediments and Greenland iceNature, 365, p. 143-147, 1993.
Lamont-Doherty Earth Observatory, Columbia University, Palisades, New York 10964, USA.
Geofysisk Afdeling, Niels Bohr Instituttet for Astronomi, Fysik og Geofysik, Københavns Universitet
Oxygen isotope measurements in Greenland ice demonstrate that a series of rapid wann-cold oscillations -called Dansgaard-Oeschger events-punctuated the last glaciation. Here we present records of sea surface temperature from North Atlantic sediments spanning the past 90 kyr which contain a series of rapid temperature oscillations closely matching those in the ice-core record, confirming predictions that the ocean must bear the imprint of the Dansgaard-Oeschger events. Moreover, we show that between 20 and 80 kyr ago, the shifts in ocean-atmosphere temperature are bundled into cooling cycles lasting on average 10 to I5 kyr, with asymmetrical saw-tooth shapes. Each cycle culminated in an enormous discharge of icebergs into the North Atlantic (a Heinrich event'), followed by an abrupt shift to a warmer climate. These cycles document a previously unrecognized link between ice sheet behaviour and ocean-atmosphere temperature changes. An important question that remains to be resolved is whether the cycles are driven by external factors, such as orbital forcing, or by internal ice-sheet dynamics.