Earth and Atmospheric Sciences, Department of



T. Naish, Victoria University of Wellington
R. D. Powell, Northern Illinois UniversityFollow
R. Levy, University of Nebraska-Lincoln
G. Wilson, University of Otago
R. Scherer, Northern Illinois University
F. Talarico, Universita` di Siena
L. Krissek, Ohio State University
F. Niessen, Alfred Wegener Institute
M. Pompilio, Istituto Nazionale di Geofisica e Vulcanologia
T. J. Wilson, Ohio State UniversityFollow
L. Carter, Victoria University of WellingtonFollow
R. DeConto, University of Massachusetts
P. Huybers, Harvard University
R. McKay, Victoria University of Wellington
D. Pollard, Pennsylvania State University
J. Ross, New Mexico Institute of Mining & Technology
D. Winter, University of Nebraska-Lincoln
P. Barrett, Victoria University of WellingtonFollow
G. Browne, Lower Hutt 5040, New Zealand
R. Cody, Victoria University of Wellington
E. A. Cowan, Appalachian State UniversityFollow
J. Crampton, Lower Hutt 5040, New Zealand
G. Dunbar, Victoria University of Wellington
N. Dunbar, New Mexico Institute of Mining & Technology
F. Florindo, Istituto Nazionale di Geofisica e Vulcanologia
C. Gebhardt, Alfred Wegener Institute
I. Graham, Lower Hutt 5040, New Zealand
M. Hannah, Victoria University of Wellington
D. Hansaraj, Victoria University of Wellington
David M. Harwood, University of Nebraska-LincolnFollow
D. Helling, . Alfred Wegener Institute
S. Henrys, Northern Illinois University
L. Hinnov, Johns Hopkins University
G. Kuhn, . Alfred Wegener Institute
P. Kyle, . New Mexico Institute of Mining & Technology
A. La¨ufer, Federal Institute of Geosciences & Natural Resources
P. Maffioli, . Universita` Milano-Bicocca
D. Magens, Alfred Wegener Institute
K. Mandernack, Colorado School of Mines
W. McIntosh, New Mexico Institute of Mining & Technology
C. Millan, Ohio State University
R. Morin, US Geological Survey
C. Ohneiser, University of Otago
T. Paulsen, University of Wisconsin-Oshkosh
D. Persico, Universita` degli Studi di Parma
I. Raine, Lower Hutt 5040, New Zealand
J. Reed, University of Nebraska-Lincoln
C. Riesselman, Stanford University
L. Sagnotti, Istituto Nazionale di Geofisica e Vulcanologia
D. Schmitt, University of Alberta, Edmonton
C. Sjunneskog, Louisiana State University
P. Strong, Lower Hutt 5040, New Zealand
M. Taviani, Bologna, Via Gobetti
S. Vogel, Northern Illinois University
T. Wilch, Albion College
T. Williams, Columbia University

Date of this Version



Published in Nature Vol 458 (19 March 2009), pp. 322-329 doi:10.1038/nature07867
Includes Supplementary Material.


Thirty years after oxygen isotope records frommicrofossils deposited in ocean sediments confirmed the hypothesis that variations in the Earth’s orbital geometry control the ice ages1, fundamental questions remain over the response of the Antarctic ice sheets to orbital cycles2. Furthermore, an understanding of the behaviour of the marinebased West Antarctic ice sheet (WAIS) during the ‘warmerthan- present’ early-Pliocene epoch ( ~5–3Myr ago) is needed to better constrain the possible range of ice-sheet behaviour in the context of future global warming3. Here we present a marine glacial record from the upper 600mof the AND-1B sediment core recovered from beneath the northwest part of the Ross ice shelf by the ANDRILL programme and demonstrate well-dated, ~40-kyr cyclic variations in ice-sheet extent linked to cycles in insolation influenced by changes in the Earth’s axial tilt (obliquity) during the Pliocene. Our data provide direct evidence for orbitally induced oscillations in the WAIS, which periodically collapsed, resulting in a switch from grounded ice, or ice shelves, to open waters in the Ross embayment when planetary temperatures were up to ~3 C warmer than today4 and atmospheric CO2 concentration was as high as ~400 p.p.m.v. (refs 5, 6). The evidence is consistent with a new ice-sheet/ice-shelf model7 that simulates fluctuations in Antarctic ice volume of up to +7min equivalent sea level associated with the loss of the WAIS and up to+3min equivalent sea level from the EastAntarctic ice sheet, in response to ocean-inducedmelting paced by obliquity.During interglacial times, diatomaceous sediments indicate high surface-water productivity, minimal summer sea ice and air temperatures above freezing, suggesting an additional influence of surface melt 8 under conditions of elevated CO2.