2025-11-25 ワシントン大学（UW）
＜関連情報＞
- https://www.washington.edu/news/2025/11/25/in-a-new-documentary-uw-researchers-investigate-when-greenland-was-ice-free/
- https://www.pnas.org/doi/10.1073/pnas.2407465121
- https://tiisys.com/blog/2023/07/22/post-124646/
- https://www.pnas.org/doi/10.1073/pnas.2021442118
グリーンランドの氷床中心部の下にある植物、昆虫、菌類の化石は、氷のない時代の証拠である Plant, insect, and fungi fossils under the center of Greenland’s ice sheet are evidence of ice-free times
Paul R. Bierman, Halley M. Mastro, Dorothy M. Peteet, +7 , and Barry Rock
Proceedings of the National Academy of Sciences Published:August 5, 2024
DOI:https://doi.org/10.1073/pnas.2407465121
Abstract
The persistence and size of the Greenland Ice Sheet (GrIS) through the Pleistocene is uncertain. This is important because reconstructing changes in the GrIS determines its contribution to sea level rise during prior warm climate periods and informs future projections. To understand better the history of Greenland’s ice, we analyzed glacial till collected in 1993 from below 3 km of ice at Summit, Greenland. The till contains plant fragments, wood, insect parts, fungi, and cosmogenic nuclides showing that the bed of the GrIS at Summit is a long-lived, stable land surface preserving a record of deposition, exposure, and interglacial ecosystems. Knowing that central Greenland was tundra-covered during the Pleistocene informs the understanding of Arctic biosphere response to deglaciation.
キャンプ・センチュリーの1.4キロメートルの氷の下に堆積した堆積物に保存された、グリーンランドの植生と氷河の歴史に関する数百万年前の記録 A multimillion-year-old record of Greenland vegetation and glacial history preserved in sediment beneath 1.4 km of ice at Camp Century
Andrew J. Christ, Paul R. Bierman, Joerg M. Schaefer, +14 , and John Southon
Proceedings of the National Academy of Sciences Published:March 15, 2021
DOI:https://doi.org/10.1073/pnas.2021442118
Significance
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.
Abstract
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.
