The Marine Record of the East Antarctic Ice Sheet

Marine deep-sea oxygen isotope records indicate that a period of ice-sheet instability during the Early and Middle Miocene is superimposed on a long-term warming trend that culminated in the late Middle Miocene climatic optimum from ~17 to 15 Ma (Miller et al., 1987; Zachos et al., 2001). This phase was followed by a gradual cooling with a major cooling event occurring at the Middle-Late Miocene boundary ~14Ma that continued for ~1-2m.y. (Flower and Kennett, 1995).

Long-term variation in the marine oxygen isotopic data (e.g. Hodell and Venz, 1992; Kennett and Hodell, 1995; Zachos et al., 2001) is suggestive of a warming in the earliest Pliocene, culminating in the mid-Pliocene Climatic Optimum at ~ 3 Ma. However, the oxygen isotope ratios do not allow major changes in ice volume on Antarctica. Obliquity-driven oscillations (41 kyr) in

818O of up to 0.6m, which dominate the Pliocene period, while capable of producing ~20-30m sea-level changes (depending on the temperature contribution to the 818O signal), are also considered insufficient to cause large-scale deglaciation of Antarctica without a significant increase in the temperature of the deep ocean.

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