Evolution of the early Antarctic ice ages

Liebrand, Diederik and de Bakker, Anouk T. M. and Beddow, Helen M. and Wilson, Paul A. and Bohaty, Steven M. and Ruessink, Gerben and Pälike, Heiko and Batenburg, Sietske J. and Hilgen, Frederik J. and Hodell, David A. and Huck, Claire E. and Kroon, Dick and Raffi, Isabella and Saes, Mischa J. M. and van Dijk, Arnold E. and Lourens, Lucas J. (2017) Evolution of the early Antarctic ice ages. Proceedings of the National Academy of Sciences, 114 (15). pp. 3867-3872. ISSN 0027-8424 DOI 10.1073/pnas.1615440114

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Official URL: http://doi.org/10.1073/pnas.1615440114

Abstract

Understanding the stability of the early Antarctic ice cap in the geological past is of societal interest because present-day atmospheric CO2 concentrations have reached values comparable to those estimated for the Oligocene and the Early Miocene epochs. Here we analyze a new high-resolution deep-sea oxygen isotope (δ18O) record from the South Atlantic Ocean spanning an interval between 30.1 My and 17.1 My ago. The record displays major oscillations in deep-sea temperature and Antarctic ice volume in response to the ∼110-ky eccentricity modulation of precession. Conservative minimum ice volume estimates show that waxing and waning of at least ∼85 to 110% of the volume of the present East Antarctic Ice Sheet is required to explain many of the ∼110-ky cycles. Antarctic ice sheets were typically largest during repeated glacial cycles of the mid-Oligocene (∼28.0 My to ∼26.3 My ago) and across the Oligocene−Miocene Transition (∼23.0 My ago). However, the high-amplitude glacial−interglacial cycles of the mid-Oligocene are highly symmetrical, indicating a more direct response to eccentricity modulation of precession than their Early Miocene counterparts, which are distinctly asymmetrical—indicative of prolonged ice buildup and delayed, but rapid, glacial terminations. We hypothesize that the long-term transition to a warmer climate state with sawtooth-shaped glacial cycles in the Early Miocene was brought about by subsidence and glacial erosion in West Antarctica during the Late Oligocene and/or a change in the variability of atmospheric CO2 levels on astronomical time scales that is not yet captured in existing proxy reconstructions.

Item Type: Article
Uncontrolled Keywords: 2017AREP; IA72
Subjects: 01 - Climate Change and Earth-Ocean Atmosphere Systems
Divisions: 01 - Climate Change and Earth-Ocean Atmosphere Systems
07 - Gold Open Access
Journal or Publication Title: Proceedings of the National Academy of Sciences
Volume: 114
Page Range: pp. 3867-3872
Identification Number: 10.1073/pnas.1615440114
Depositing User: Sarah Humbert
Date Deposited: 20 Apr 2017 21:12
Last Modified: 20 Apr 2017 21:12
URI: http://eprints.esc.cam.ac.uk/id/eprint/3947

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