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Journal Article
Seierstad, IK, Abbott PM, Bigler M, Blunier T, Bourne AJ, Brook E, Buchardt SL, Buizert C, Clausen HB, Cook E, Dahl-Jensen D, Davies SM, Guillevic M, Johnsen SJ, Pedersen DS, Popp TJ, Rasmussen SO, Severinghaus JP, Svensson A, Vinther BM.  2014.  Consistently dated records from the Greenland GRIP, GISP2 and NGRIP ice cores for the past 104 ka reveal regional millennial-scale delta O-18 gradients with possible Heinrich event imprint. Quaternary Science Reviews. 106:29-46.   10.1016/j.quascirev.2014.10.032   AbstractWebsite

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 (CH4 concentration and delta N-15 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 delta O-18 temperature-proxy records from NGRIP, GRIP, and GISP2 are generally very similar and display synchronous behaviour at climate transitions. The 1180 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 delta O-18 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 (SST) on orbital timescales, and that changing sea-ice extent and SSTs are the driving mechanisms on shorter timescales. Finally, we observe that maxima in the Summit NGRIP delta O-18 difference are roughly coincident with prominent Heinrich events. This suggests that the climatic reorganization that takes place during stadials with Heinrich events, possibly driven by a southward expansion of sea ice and low SSTs in the North Atlantic, are recorded in the ice-core records. (C) 2014 Elsevier Ltd. All rights reserved.

Taylor, KC, Mayewski PA, Alley RB, Brook EJ, Gow AJ, Grootes PM, Meese DA, Saltzman ES, Severinghaus JP, Twickler MS, White JWC, Whitlow S, Zielinski GA.  1997.  The Holocene Younger Dryas transition recorded at Summit, Greenland. Science. 278:825-827.   10.1126/science.278.5339.825   AbstractWebsite

Analysis of ice from Dye-3, Greenland, has demonstrated that the transition between the Younger Dryas and Holocene climate periods occurred over a 40-year period. A near annually resolved, multiparameter record of the transition recorded in the GISP2 core from Summit, Greenland, shows that most of the transition occurred in a series of steps with durations of about 5 years. Some climate proxies associated with more northern regions. Changes in atmospheric water vapor are likely to have played a large role in the climate transition.

Baggenstos, D, Severinghaus JP, Mulvaney R, McConnell JR, Sigl M, Maselli O, Petit JR, Grente B, Steig EJ.  2018.  A horizontal ice core from Taylor Glacier, its implications for Antarctic climate history, and an improved Taylor Dome ice core time scale. Paleoceanography and Paleoclimatology. 33:778-794.   10.1029/2017pa003297   AbstractWebsite

Ice core records from Antarctica show mostly synchronous temperature variations during the last deglacial transition, an indication that the climate of the entire continent reacted as one unit to the global changes. However, a record from the Taylor Dome ice core in the Ross Sea sector of East Antarctica has been suggested to show a rapid warming, similar in style and synchronous with the Oldest Dryas-Bolling warming in Greenland. Since publication of the Taylor Dome record, a number of lines of evidence have suggested that this interpretation is incorrect and reflects errors in the underlying time scale. The issues raised regarding the dating of Taylor Dome currently linger unresolved, and the original time scale remains the de facto chronology. We present new water isotope and chemistry data from nearby Taylor Glacier to resolve the confusion surrounding the Taylor Dome time scale. We find that the Taylor Glacier record is incompatible with the original interpretation of the Taylor Dome ice core, showing that the warming in the area was gradual and started at similar to 18 ka BP (before 1950) as seen in other East Antarctic ice cores. We build a consistent, up-to-date Taylor Dome chronology from 0 to 60 ka BP by combining new and old age markers based on synchronization to other ice core records. The most notable feature of the new TD2015 time scale is a gas age-ice age difference of up to 12,000 years during the Last Glacial Maximum, by far the largest ever observed.