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Christ et al. 2021

Christ, A.J., P.R. Bierman, J.M. Schaefer, D. Dahl-Jensen, J.P. Steffensen, L.B. Corbett, D.M. Peteet, E.K. Thomas, E.J. Steig, T.M. Rittenour, J.-L. Tison, P.-H. Blard, N. Perdrial, D.P. Dethier, A. Lini, A.J. Hidy, M.W. Caffee, and J. Southon, 2021: A multimillion-year-old record of Greenland vegetation and glacial history preserved in sediment beneath 1.4 km of ice at Camp Century. Proc. Natl. Acad. Sci., 118, no. 13, e2021442118, doi:10.1073/pnas.2021442118.

Understanding Greenland Ice Sheet history is critical for predicting its response to future climate warming and contribution to sea-level rise. We analyzed sediment at the bottom of the Camp Century ice core, collected 120 km from the coast in northwestern Greenland. The sediment, frozen under nearly 1.4 km of ice, contains well-preserved fossil plants and biomolecules sourced from at least two ice-free warm periods in the past few million years. Enriched stable isotopes in pore ice indicate precipitation at lower elevations than present, implying ice-sheet absence. The similarity of cosmogenic isotope ratios in the upper-most sediment to those measured in bedrock near the center of Greenland suggests that the ice sheet melted and re-formed at least once during the past million years.Understanding the history of the Greenland Ice Sheet (GrIS) is critical for determining its sensitivity to warming and contribution to sea level; however, that history is poorly known before the last interglacial. Most knowledge comes from interpretation of marine sediment, an indirect record of past ice-sheet extent and behavior. Subglacial sediment and rock, retrieved at the base of ice cores, provide terrestrial evidence for GrIS behavior during the Pleistocene. Here, we use multiple methods to determine GrIS history from subglacial sediment at the base of the Camp Century ice core collected in 1966. This material contains a stratigraphic record of glaciation and vegetation in northwestern Greenland spanning the Pleistocene. Enriched stable isotopes of pore-ice suggest precipitation at lower elevations implying ice-sheet absence. Plant macrofossils and biomarkers in the sediment indicate that paleo-ecosystems from previous interglacial periods are preserved beneath the GrIS. Cosmogenic ²⁶Al/¹⁰Be and luminescence data bracket the burial of the lower-most sediment between < 3.2±0.4 Ma and > 0.7 to 1.4 Ma. In the upper-most sediment, cosmogenic ²⁶Al/¹⁰Be data require exposure within the last 1.0±0.1 My. The unique subglacial sedimentary record from Camp Century documents at least two episodes of ice-free, vegetated conditions, each followed by glaciation. The lower sediment derives from an Early Pleistocene GrIS advance. ²⁶Al/¹⁰Be ratios in the upper-most sediment match those in subglacial bedrock from central Greenland, suggesting similar ice-cover histories across the GrIS. We conclude that the GrIS persisted through much of the Pleistocene but melted and reformed at least once since 1.1 Ma. All study data are included in the article and/or SI Appendix.

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@article{ch04310e,
  author={Christ, A. J. and Bierman, P. R. and Schaefer, J. M. and Dahl-Jensen, D. and Steffensen, J. P. and Corbett, L. B. and Peteet, D. M. and Thomas, E. K. and Steig, E. J. and Rittenour, T. M. and Tison, J.-L. and Blard, P.-H. and Perdrial, N. and Dethier, D. P. and Lini, A. and Hidy, A. J. and Caffee, M. W. and Southon, J.},
  title={A multimillion-year-old record of Greenland vegetation and glacial history preserved in sediment beneath 1.4 km of ice at Camp Century},
  year={2021},
  journal={Proceedings of the National Academy of Sciences},
  volume={118},
  number={13},
  pages={e2021442118},
  doi={10.1073/pnas.2021442118},
}

TY  - JOUR
ID  - ch04310e
AU  - Christ, A. J.
AU  - Bierman, P. R.
AU  - Schaefer, J. M.
AU  - Dahl-Jensen, D.
AU  - Steffensen, J. P.
AU  - Corbett, L. B.
AU  - Peteet, D. M.
AU  - Thomas, E. K.
AU  - Steig, E. J.
AU  - Rittenour, T. M.
AU  - Tison, J.-L.
AU  - Blard, P.-H.
AU  - Perdrial, N.
AU  - Dethier, D. P.
AU  - Lini, A.
AU  - Hidy, A. J.
AU  - Caffee, M. W.
AU  - Southon, J.
PY  - 2021
TI  - A multimillion-year-old record of Greenland vegetation and glacial history preserved in sediment beneath 1.4 km of ice at Camp Century
JA  - Proc. Natl. Acad. Sci.
JO  - Proceedings of the National Academy of Sciences
VL  - 118
IS  - 13
SP  - e2021442118
DO  - 10.1073/pnas.2021442118
ER  -

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