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Miocene and Pliocene ice and air from the Allan Hills blue ice area, East Antarctica.

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Title: Miocene and Pliocene ice and air from the Allan Hills blue ice area, East Antarctica.
Authors: Shackleton, S.1,2 sarah.shackleton@whoi.edu, Hishamunda, V.1, Davidge, L.3, Brook, E.4, Peterson, J. Marks4, Carter, A.5, Aarons, S.5, Kurbatov, A.6, Introne, D.6, Yan, Y.7, Nesbitt, M.6, Buizert, C.4, Steig, E. J.3, Schauer, A. J.3, Morgan, J.5, Neff, P. D.8, Epifanio, J. A.4, Severinghaus, J.5, Bender, M.1,9, Higgins, J. A.1 jahiggin@princeton.edu
Source: Proceedings of the National Academy of Sciences of the United States of America. 11/4/2025, Vol. 122 Issue 44, p1-6. 17p.
Subjects: Antarctic ice, Ice cores, Miocene Epoch, Stable isotopes, Paleoclimatology, Glaciers, Antarctic climate, Pliocene Epoch
Geographic Terms: Antarctica, East Antarctica (Antarctica)
Abstract: Antarctic ice cores provide a unique archive of Earth’s atmosphere and its largest extant ice sheet. The oldest continuous ice core extends back 800 ky, though discontinuous ice cores from the Allan Hills blue ice area (BIA) have been shown to preserve snapshots of ice and air back to at least 2.7 million years ago (Ma). Here, we provide snapshots of putatively Miocene and Pliocene ice and air from shallow ice cores drilled in the Allan Hills BIA. The ice, dated using the deficit in 40Ar in ancient air compared to the modern atmosphere, is stratigraphically complex. Nevertheless, surface temperatures inferred from water isotopes correlate with sample age and indicate 12 ± 2 °C of cooling in Antarctica between 6 Ma and the late Pleistocene. Basal ice is nearly devoid of gases and remains to be dated with existing methods. This undated ice is characterized by an isotopic temperature 5 ± 1 °C warmer than the oldest dated (6 million year old) sample. We speculate that this ice reflects surface snowpack or permafrost that was preserved by the growth of the East Antarctic ice sheet in the Middle to Late Miocene. [ABSTRACT FROM AUTHOR]
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Abstract:Antarctic ice cores provide a unique archive of Earth’s atmosphere and its largest extant ice sheet. The oldest continuous ice core extends back 800 ky, though discontinuous ice cores from the Allan Hills blue ice area (BIA) have been shown to preserve snapshots of ice and air back to at least 2.7 million years ago (Ma). Here, we provide snapshots of putatively Miocene and Pliocene ice and air from shallow ice cores drilled in the Allan Hills BIA. The ice, dated using the deficit in 40Ar in ancient air compared to the modern atmosphere, is stratigraphically complex. Nevertheless, surface temperatures inferred from water isotopes correlate with sample age and indicate 12 ± 2 °C of cooling in Antarctica between 6 Ma and the late Pleistocene. Basal ice is nearly devoid of gases and remains to be dated with existing methods. This undated ice is characterized by an isotopic temperature 5 ± 1 °C warmer than the oldest dated (6 million year old) sample. We speculate that this ice reflects surface snowpack or permafrost that was preserved by the growth of the East Antarctic ice sheet in the Middle to Late Miocene. [ABSTRACT FROM AUTHOR]
ISSN:00278424
DOI:10.1073/pnas.2502681122