Millennial Cycles in Climate Records From the Western Ice-
land Sea During Isotope Stage 3
A H L Voelker and M Sarnthein (both at: SFB313 and GPI, Kiel University, 24118 Kiel, Germany; ph. +49-431-880-4685; fax +49-431-880-1569; e-mail: email@example.com); H Erlenkeuser and P M Grootes (Leibniz Labor, Kiel University, 24118 Kiel, Germany); F Niessen and O Swientek (Alfred-Wegener-Inst., 27515 Bremerhaven, Germany)
The millennial-scale Dansgaard-Oeschger cycles are probably linked to
changes in the thermohaline circulation of the North Atlantic. To determine the causal links of these oscillations we studied well dated, high resolution climate records of sediment core PS2644 (67.867N, 21.765W, 780 m w.d.), a core position that monitors past variations in (1) the incursion of North Atlantic surface water via the Irminger Current, (2) the meltwater supply from the neighboring continents (i.e., Iceland and Greenland) and (3) the outflow of intermediate/ deep water across the Denmark Strait. The records of plank-tic stable-isotopes and ice-rafted debris (IRD) were analyzed with an average time resolution of 50yr during stage 3 and reveal several meltwater spikes. These events correlate with the numerous stadials between and cold rebounds within warm Dansgaard-Oeschger events in the GISP2 oxygen isotope record. The most prominent events are assigned to Heinrich events 1-6 and immediately precede the major warming episodes on Greenland. In PS2644, the interstadials are documented by heavier isotope values and higher sea surface temperatures (i.e., less % N. pachy. (s), which imply an enhanced incursion of Atlantic water and thus, an intensification of the thermohaline circulation as soon as the meltwater has disappeared. The intensified circulation is also revealed by an increased abundance of epibenthic Cibicides sp., higher magnetic susceptibility values and finally, much higher sedimentation rates on the leeside of the Denmark Strait.
Spectral analysis of the oxygen isotope record shows dominant periods of 8550yr, 3380yr and 1590yr at 29-58 cal ka, similar to those in the GISP2 temperature record (3370yr, 1480yr). The IRD cycles occur near periods of 3100yr and 1710yr. The abundance of the epibenthic Cibicides sp. reveals periods of 5000yr, 2400yr and 1500yr. Cross spectral analyses promise detailed insights into leads and lags between the various climatic signals, including the actual causal links between changes in the Atlantic thermohaline circulation, meltwater events in the northern North Atlantic and atmospheric temperature oscillations above Greenland.