LINKING pCO2 ESTIMATES AND OCEANOGRAPHIC AND ANTARCTIC CLIMATE RECORDS FOR THE EARLY ICEHOUSE WORLD (34-16 Ma)

An evaluation of recently published calibrated isotopic records, global sea-level estimates from backstripped stratigraphic records, stratigraphic and biological data from Antarctica, and estimates of atmospheric pCO₂ shows that they are strongly linked during the Oligocene to early Miocene (34-16 Ma). While non-calibrated isotopic data appear not to match the other records, particularly for the span from 26-16 Ma, calibration against sea-level estimates obtained from backstripping continental margin stratigraphy results in excellent agreement. This resolves discrepancies between δ¹⁸O records and other climate proxies. The calibrated δ¹⁸O records also provide new estimates of ice volume, suggesting that the East Antarctic Ice Sheet (EAIS) grew to as much as 30% greater than the present-day ice volume at glacial maxima during that span. This conclusion is corroborated by seismic and stratigraphic data from the Antarctic margin that suggest that the ice sheet may have covered much of the continental shelf during Oligocene and early Miocene glacial maxima. Palynological data suggest long-term cooling during the Oligocene, with cold near tundra environments developing along the coast during glacial minima no later than the late Oligocene. A possible mechanism for this long-term cooling is a decrease in atmospheric pCO₂ from the middle Eocene to Oligocene, reaching near pre-industrial levels by the latest Oligocene and remaining at those levels throughout the Miocene