Orbitally induced oscillations in the East Antarctic ice sheet at the Oligocene/Miocene boundary

Details Orbitally induced oscillations in the East Antarctic ice sheet at the Oligocene/Miocene boundary Orbitally induced oscillations in the East Antarctic ice sheet at the Oligocene/Miocene boundary

Oct 2001

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2001natur.413..719n&link_type=abstract

Nature, Volume 413, Issue 6857, pp. 719-723 (2001).

Physics

29

Scientific paper

Between 34 and 15million years (Myr) ago, when planetary temperatures were 3-4°C warmer than at present and atmospheric CO2 concentrations were twice as high as today, the Antarctic ice sheets may have been unstable. Oxygen isotope records from deep-sea sediment cores suggest that during this time fluctuations in global temperatures and high-latitude continental ice volumes were influenced by orbital cycles. But it has hitherto not been possible to calibrate the inferred changes in ice volume with direct evidence for oscillations of the Antarctic ice sheets. Here we present sediment data from shallow marine cores in the western Ross Sea that exhibit well dated cyclic variations, and which link the extent of the East Antarctic ice sheet directly to orbital cycles during the Oligocene/Miocene transition (24.1-23.7Myr ago). Three rapidly deposited glacimarine sequences are constrained to a period of less than 450kyr by our age model, suggesting that orbital influences at the frequencies of obliquity (40kyr) and eccentricity (125kyr) controlled the oscillations of the ice margin at that time. An erosional hiatus covering 250kyr provides direct evidence for a major episode of global cooling and ice-sheet expansion about 23.7Myr ago, which had previously been inferred from oxygen isotope data (Mi1 event).

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