Atmospheric Carbon Dioxide and Climate Following the Middle Miocene Expansion of the East Antarctic Ice Sheet

Badger, M. P.; Lear, C. H.; Pancost, R. D.; Bailey, T. R.; Leng, M. J. and Abels, H. A. (2008). Atmospheric Carbon Dioxide and Climate Following the Middle Miocene Expansion of the East Antarctic Ice Sheet. In: EOS, Transactions, American Geophysical Union, 89(53), article no. PP43D-08.

URL: http://abstractsearch.agu.org/meetings/2008/FM/PP4...

Abstract

The Middle Miocene Climate Transition (MMCT) represents a major step, as represented by global oxygen isotope records, from the greenhouse world of the Cretaceous to the icehouse world of the present day. The transition, which is recorded by a δ18O shift of >1‰, has long been associated with a major build-up of ice on East Antarctica. Major changes in the carbon system have been recorded in both the lead-up to the MMCT (the "Monterey Excursion"), and also at the MMCT itself, culminating with a >1.2‰ transient shift in inorganic δ13C immediately following ice build-up ("CM6"). Traditional interpretations suggest that the carbon isotope excursions represent increased burial of organic carbon, which led to a drawdown of carbon dioxide from the atmosphere. More recently, it has been proposed that a reduction in silicate weathering following the growth of the ice sheet led to increased atmospheric carbon dioxide over CM6. We present high resolution coupled multi-proxy records of the 1.1 million years following the MMCT and use alkenone paleobarometry to reconstruct atmospheric CO2 across CM6 to test these hypotheses. Our records shed new light on the cause of this major positive carbon isotope excursion and may have implications as to what controls climate at this point in the Cenozoic.

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