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|Authors: ||Naish, T.*|
|Title: ||Obliquity-paced Pliocene West Antarctic ice sheet oscillations|
|Title of journal: ||Nature|
|Series/Report no.: ||7236 / 458 (2009)|
|Issue Date: ||19-Mar-2009|
|Abstract: ||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 marine-based West Antarctic ice sheet (WAIS) during the ‘warmer-than-
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 600 m of theAND-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
+ 7 m in equivalent sea level associated with the loss of the WAIS and up to +3 m in equivalent sea level from the EastAntarctic ice sheet, in response to ocean-induced melting 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 melt8 under
conditions of elevated CO2.|
|Appears in Collections:||Papers Published / Papers in press|
03.01.06. Paleoceanography and paleoclimatology
02.02.99. General or miscellaneous
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