Potential links between surging ice sheets, circulation changes, and the Dansgaard-Oeschger Cycles in the Irminger Sea, 60–18 Kyr
Article first published online: 4 MAY 2010
Copyright 2000 by the American Geophysical Union.
Volume 15, Issue 4, pages 425–442, August 2000
How to Cite
2000), Potential links between surging ice sheets, circulation changes, and the Dansgaard-Oeschger Cycles in the Irminger Sea, 60–18 Kyr, Paleoceanography, 15(4), 425–442, doi:10.1029/1999PA000464., , , , , , , and (
- Issue published online: 4 MAY 2010
- Article first published online: 4 MAY 2010
- Manuscript Accepted: 22 MAR 2000
- Manuscript Received: 5 OCT 1999
Surface and deepwater paleoclimate records in Irminger Sea core SO82-5 (59°N, 31°W) and Icelandic Sea core PS2644 (68°N, 22°W) exhibit large fluctuations in thermohaline circulation (THC) from 60 to 18 calendar kyr B.P., with a dominant periodicity of 1460 years from 46 to 22 calendar kyr B.P., matching the Dansgaard-Oeschger (D-O) cycles in the Greenland Ice Sheet Project 2 (GISP2) temperature record [Grootes and Stuiver, 1997]. During interstadials, summer sea surface temperatures (SSTsu) in the Irminger Sea averaged to 8°C, and sea surface salinities (SSS) averaged to ∼36.5, recording a strong Irminger Current and Atlantic THC. During stadials, SSTsu dropped to 2°–4°C, in phase with SSS drops by ∼1–2. They reveal major meltwater injections along with the East Greenland Current, which turned off the North Atlantic deepwater convection and hence the heat advection to the north, in harmony with various ocean circulation and ice models. On the basis of the IRD composition, icebergs came from Iceland, east Greenland, and perhaps Svalbard and other northern ice sheets. However, the southward drifting icebergs were initially jammed in the Denmark Strait, reaching the Irminger Sea only with a lag of 155–195 years. We also conclude that the abrupt stadial terminations, the D-O warming events, were tied to iceberg melt via abundant seasonal sea ice and brine water formation in the meltwater-covered northwestern North Atlantic. In the 1/1460-year frequency band, benthic δ18O brine water spikes led the temperature maxima above Greenland and in the Irminger Sea by as little as 95 years. Thus abundant brine formation, which was induced by seasonal freezing of large parts of the northwestern Atlantic, may have finally entrained a current of warm surface water from the subtropics and thereby triggered the sudden reactivation of the THC. In summary, the internal dynamics of the east Greenland ice sheet may have formed the ultimate pacemaker of D-O cycles.