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 AD 2000), corresponding to Marine Isotope Stage 2 (MIS 2) and the end of MIS 3. The matching provides a basis for applying the recent NGRIP-based Greenland Ice Core Chronology 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 d18O 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 between the d18O 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.
The file contains the match points used for the transfer of the GICC05 time scale from NGRIP to GRIP and GISP2. The three cores have been matched using mainly volcanic markers. The uncertainty of the match point depths is discussed in the Quat. Sci. Res. paper.The NGRIP1 core reaches down to a depth of 1372 m. The NGRIP2 core (drilled 20 meters away from the NGRIP1 core) reaches from surface to bedrock, but high-resolution measurements have only been carried out downwards from 1346 m. In the 26 m overlap zone, the cores are offset by 0.43 m on average, probably due to uncertainties in the logging procedure (see Schøtt Hvidberg et al., Ann. Glac. 35, 2002). Thus, the same features appear at larger depths in the NGRIP1 than in the NGRIP2 core. The first 5 match points are given as NGRIP1 depths, while the remaining depths are NGRIP2 depths.The match points down to 1609.45 m NGRIP depth have been published in Rasmussen et al. 2006.The remaining part of the match points are related to work described in Rasmussen et al. 2008.See also Centre for Ice and Cllimate at http://www.iceandclimate.nbi.ku.dk/data