Editor's Summary
19 March 2009
When the ice sheet melted
Changes in Earth's orbit are known to influence climate shifts from cold glacials to warm interglacials. How the vast West Antarctic ice sheet responds to these fluctuations is uncertain but, because its collapse could raise sea levels by about 5 metres, of great interest. Naish et al. have analysed the AND-1B ocean sediment core, extracted from beneath the Ross Ice Shelf as part of the ANDRILL drilling project, and find evidence that the ice sheet collapsed periodically during the early Pliocene (3-5 million years ago), when atmospheric CO2 levels were similar to, or slightly higher than today's. The pattern of collapse suggests an influence of approximately 40,000-year cycles in the tilt of Earth's rotational axis (obliquity). Also in this issue of Nature, in a numerical modelling study focused on the past 5 million years in Antarctica, David Pollard and Robert DeConto combine ice sheet (land-supported) and ice shelf (water-supported) modelling approaches to simulate the movement of the grounding line — the border between land and sea ice. Their results show that over the past 5 million years, the West Antarctic ice sheet transitioned between full, intermediate, and collapsed states in just a few thousand years. This means that the ice sheet is likely to disintegrate if ocean temperatures in the area rise by 5 C.
News and Views: Global change: West-side story of Antarctic ice
During the past five million years, the West Antarctic ice sheet has waxed and waned in size. A two-pronged reconstruction of that history provides clues to the ice sheet's future behaviour.
Philippe Huybrechts
doi:10.1038/458295a
Letter: Obliquity-paced Pliocene West Antarctic ice sheet oscillations
T. Naish, R. Powell, R. Levy, G. Wilson, R. Scherer, F. Talarico, L. Krissek, F. Niessen, M. Pompilio, T. Wilson, L. Carter, R. DeConto, P. Huybers, R. McKay, D. Pollard, J. Ross, D. Winter, P. Barrett, G. Browne, R. Cody, E. Cowan, J. Crampton, G. Dunbar, N. Dunbar, F. Florindo, C. Gebhardt, I. Graham, M. Hannah, D. Hansaraj, D. Harwood, D. Helling, S. Henrys, L. Hinnov, G. Kuhn, P. Kyle, A. Läufer, P. Maffioli, D. Magens, K. Mandernack, W. McIntosh, C. Millan, R. Morin, C. Ohneiser, T. Paulsen, D. Persico, I. Raine, J. Reed, C. Riesselman, L. Sagnotti, D. Schmitt, C. Sjunneskog, P. Strong, M. Taviani, S. Vogel, T. Wilch & T. Williams
doi:10.1038/nature07867
First paragraph | Full Text | PDF (1,456K) | Supplementary information
Letter: Modelling West Antarctic ice sheet growth and collapse through the past five million years
David Pollard & Robert M. DeConto
doi:10.1038/nature07809
First paragraph | Full Text | PDF (1,246K) | Supplementary information
