Consistently dated records from the Greenland GRIP, GISP2 and NGRIP ice cores for the past 104ka reveal regional millennial-scale δ18O gradients with possible Heinrich event imprint

• Main Authors: Seierstad, Inger K, Abbott, Peter M, Bigler, Matthias, Blunier, Thomas, Bourne, Anna 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: unknown
• Published: eScholarship, University of California 2014
• Subjects: Climate Action; Paleoclimate; Greenland ice cores; GICC05 chronology; Tephra isochrons; Regional climate; Water isotopes; Heinrich event; Earth Sciences; History and Archaeology; Paleontology; Greenland; Pacific; Greenland ice core; GRIP; ice core; Ice Sheet; NGRIP; North Atlantic; Sea ice
• Online Access: https://escholarship.org/uc/item/4gj5n8gn

We present a synchronization of the NGRIP, GRIP and GISP2 ice cores onto a master chronology extending back to 104ka 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 (CH4 concentration and δ15N of N2). 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 δ18O temperature-proxy records from NGRIP, GRIP, and GISP2 are generally very similar and display synchronous behaviour at climate transitions. The δ18O 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 δ18O 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 temperatures ...