Consistently dated records from the Greenland GRIP, GISP2 and NGRIP ice cores for the past 104 ka reveal regional millennial-scale δ 18 O gradients with possible Heinrich event imprint

• Published in: Quaternary Science Reviews
• Main Authors: Seierstad, Inger K., Abbott, Peter M., Bigler, Matthias, Blunier, Thomas, Bourne, A.J., Brook, Edward, Buchardt, Susanne L., Buizert, Christo, Clausen, Henrik B., Cook, Eliza, Dahl-Jensen, Dorthe, Davies, Siwan M., Guillevic, Myriam, Johnsen, Sigfús J., Pedersen, Desirée S., Popp, Trevor J., Rasmussen, Sune O., Severinghaus, Jeffrey P., Svensson, Anders, Vinther, Bo M.
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2014
• Subjects: Greenland; Pacific; Greenland ice core; GRIP; ice core; Ice Sheet; NGRIP; North Atlantic; Sea ice
• Online Access: https://eprints.soton.ac.uk/405034/

We present a synchronization of the NGRIP, GRIP and GISP2 ice cores onto a master chronology extending back to 104 ka before present, providing a consistent chronological framework for these three Greenland records. The synchronization aligns distinct peaks in volcanic proxy records and other impurity records (chemo-stratigraphic matching) and assumes that these layers of elevated impurity content represent the same, instantaneous event in the past at all three sites. More than 900 marker horizons between the three cores have been identified and our matching is independently confirmed by 24 new and previously identified volcanic ash (tephra) tie-points. Using the reference horizons, we transfer the widely used Greenland ice-core chronology, GICC05modelext, to the two Summit cores, GRIP and GISP2. Furthermore, we provide gas chronologies for the Summit cores that are consistent with the GICC05modelext timescale by utilizing both existing and new gas data (CH 4 concentration and δ 15 N of N 2 ). We infer that the accumulation contrast between the stadial and interstadial phases of the glacial period was ~10% greater at Summit compared to at NGRIP. The δ 18 O temperature-proxy records from NGRIP, GRIP, and GISP2 are generally very similar and display synchronous behaviour at climate transitions. The δ 18 O differences between Summit and NGRIP, however, changed slowly over the Last Glacial–Interglacial cycle and also underwent abrupt millennial-to-centennial-scale variations. We suggest that this observed latitudinal δ 18 O gradient in Greenland during the glacial period is the result of 1) relatively higher degree of precipitation with a Pacific signature at NGRIP, 2) increased summer bias in precipitation at Summit, and 3) enhanced Rayleigh distillation due to an increased source-to-site distance and a potentially larger source-to-site temperature gradient. We propose that these processes are governed by changes in the North American Ice Sheet (NAIS) volume and North Atlantic sea-ice extent and/or sea-surface ...