Synchronization of the NGRIP, GRIP, and GISP2 ice cores across MIS 2 and palaeoclimatic implications

Quaternary Science Reviews, in press, 2007
S.O. Rasmussen, I.K. Seierstad, K.K. Andersen, M. Bigler, D. Dahl-Jensen and S.J. Johnsen
Ice and Climate, The Niels Bohr Institute, Juliane Maries Vej 30, DK-2100 Copenhagen, Denmark

We here present a synchronization of the NGRIP, GRIP, and GISP2 ice cores based mainly on volcanic events over the period 14.9-32.45 ka b2k (before A.D. 2000), cor- responding to Marine Isotope Stage 2 (MIS 2) and the end of MIS 3. The matching provides a means to apply the recent NGRIP-based Greenland Ice Core Chronol- ogy 2005 (GICC05) time scale to the GRIP and GISP2 ice cores, thereby making it possible to compare the synchronized palaeoclimate profiles of the cores in detail and to identify relative accumulation differences between the cores. Based on the matching, a period of anomalous high accumulation rates in the GISP2 ice core is detected within the period 16.5-18.3 ka b2k. The δ18O and [Ca2+] profiles of the three cores are presented on the common GICC05 time scale and generally show excellent agreement across the stadial-interstadial transitions and across the two characteristic dust events in Greenland Stadial 3. However, large differences be- tween the δ18O and [Ca2+] profiles of the three cores are seen in the same period as the 7 - 9% increase in the GISP2 accumulation rate. We conclude that changes of the atmospheric circulation are likely to have occurred in this period, altering the spatial gradients in Greenland and resulting in larger variations between the records.