Miocene and Pliocene ice and air from the Allan Hills blue ice area, East 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 40 Ar 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.
Article Details
Journal Info
Proceedings of the National Academy of Sciences
National Academy of Sciences
Authors (20)
S. Shackleton
Department of Geosciences, Princeton University
V. Hishamunda
Department of Geosciences, Princeton University
L. Davidge
Department of Earth & Space Sciences, University of Washington
E. Brook
College of Earth, Ocean, and Atmospheric Sciences, Oregon State University
J. Marks Peterson
College of Earth, Ocean, and Atmospheric Sciences, Oregon State University
A. Carter
S. Aarons
Scripps Institution of Oceanography, University of California San Diego
A. Kurbatov
Climate Change Institute, University of Maine
D. Introne
Climate Change Institute, University of Maine
Y. Yan
State Key Laboratory of Marine Geology, Tongji University
I. M. Nesbitt
Climate Change Institute, University of Maine
C. Buizert
College of Earth, Ocean, and Atmospheric Sciences, Oregon State University
E. J. Steig
Department of Earth & Space Sciences, University of Washington
A. J. Schauer
Department of Earth & Space Sciences, University of Washington
J. Morgan
Scripps Institution of Oceanography, University of California San Diego
P. D. Neff
Department of Soil, Water, and Climate, University of Minnesota
J. A. Epifanio
College of Earth, Ocean, and Atmospheric Sciences, Oregon State University
J. Severinghaus
Scripps Institution of Oceanography, University of California San Diego
M. Bender
Department of Geosciences, Princeton University
J. A. Higgins
Department of Geosciences, Princeton University