Cooling and ice growth across the Eocene-Oligocene transition

The Eocene-Oligocene (E-O) climate transition (ca. 34 Ma) marks a period of Antarctic ice growth and a major step from early Cenozoic greenhouse conditions toward today's glaciated climate state. The transition is represented by an increase in deep-sea benthic foraminiferal oxygen isotope (18O) values occurring in two main steps that reflect the temperature and 18O of seawater. Existing benthic Mg/Ca paleotemperature records do not display a cooling across the transition, possibly reflecting a saturation state effect on benthic foraminiferal Mg/Ca ratios at deep-water sites. Here we present data from exceptionally well preserved foraminifera deposited well above the calcite compensation depth that provide the first proxy evidence for an 2.5 °C ocean cooling associated with the ice growth. This permits interpretation of E-O 18O records without invoking Northern Hemisphere continental-scale ice.

[1]  David Pollard,et al.  Rapid Cenozoic glaciation of Antarctica induced by declining atmospheric CO2 , 2003, Nature.

[2]  Henry Elderfield,et al.  Calibration of Mg/Ca thermometry in planktonic foraminifera from a sediment trap time series , 2003 .

[3]  H. Elderfield,et al.  A study of cleaning procedures used for foraminiferal Mg/Ca paleothermometry , 2003 .

[4]  Niall C. Slowey,et al.  Benthic foraminiferal Mg/Ca-paleothermometry: a revised core-top calibration , 2002 .

[5]  P. Bown,et al.  Stratigraphy and sedimentology of the Upper Cretaceous to Paleogene Kilwa Group, southern coastal Tanzania , 2006 .

[6]  L. Sloan,et al.  Evidence from the Antarctic continental margin of Late Paleogene ice sheets: a manifestation of plate reorganization and synchronous changes in atmospheric circulation over the emerging Southern Ocean? , 1992 .

[7]  D. Schrag,et al.  Application of benthic foraminiferal Mg/Ca ratios to questions of Cenozoic climate change , 2002 .

[8]  Henry Elderfield,et al.  Calibrations for benthic foraminiferal Mg/Ca paleothermometry and the carbonate ion hypothesis , 2006 .

[9]  R. DeConto,et al.  Rapid Cenozoic glaciation of Antarctica induced by declining atmospheric CO2 , 2003, Nature.

[10]  P. Pearson,et al.  The Eocene-Oligocene transition , 2007 .

[11]  K. Miller,et al.  Calibration between eustatic estimates from backstripping and oxygen isotopic records for the Oligocene , 2002 .

[12]  Edward A. Boyle,et al.  Comparison of Atlantic and Pacific paleochemical records for the last 215,000 years : changes in deep ocean circulation and chemical inventories , 1985 .

[13]  J. Zachos,et al.  Carbon cycle feedbacks and the initiation of Antarctic glaciation in the earliest Oligocene , 2005 .

[14]  S. Cande,et al.  Revised calibration of the geomagnetic polarity timescale for the Late Cretaceous and Cenozoic , 1995 .

[15]  R. DeConto,et al.  Sea ice feedback and Cenozoic evolution of Antarctic climate and ice sheets , 2007 .

[16]  David K. Rea,et al.  Paleogene calcite compensation depth in the eastern subtropical Pacific: Answers and questions , 2005 .

[17]  N. Shackleton,et al.  Paleotemperature History of the Cenozoic and the Initiation of Antarctic Glaciation: Oxygen and Carbon Isotope Analyses in DSDP Sites 277, 279 and 281 , 1975 .

[18]  L. Sloan,et al.  Trends, Rhythms, and Aberrations in Global Climate 65 Ma to Present , 2001, Science.

[19]  J. Erez,et al.  Experimental paleotemperature equation for planktonic foraminifera , 1983 .

[20]  J. Kennett.  Cenozoic evolution of Antarctic glaciation the Circum-Antarctic Ocean and their impact on global paleoceanography , 1977 .

[21]  P. Pearson,et al.  Stable warm tropical climate through the Eocene Epoch , 2007 .

[22]  H. Elderfield,et al.  A Cenozoic seawater Sr/Ca record from benthic foraminiferal calcite and its application in determining global weathering fluxes , 2003 .

[23]  Caroline H. Lear,et al.  Late Eocene to early Miocene ice sheet dynamics and the global carbon cycle , 2004 .

[24]  B. Wilkinson,et al.  Sedimentary carbonate record of calcium-magnesium cycling , 1989 .

[25]  T. Marchitto,et al.  Mg/Ca temperature calibration for the benthic foraminifer Cibicidoides pachyderma , 2007 .

[26]  Bridget S. Wade,et al.  Extinction and environmental change across the Eocene-Oligocene boundary in Tanzania , 2008 .

[27]  J. Zachos,et al.  Marked Decline in Atmospheric Carbon Dioxide Concentrations During the Paleogene , 2005, Science.

[28]  A. Roberts,et al.  Continental ice in Greenland during the Eocene and Oligocene , 2007, Nature.

[29]  H. Elderfield,et al.  Cenozoic deep-Sea temperatures and global ice volumes from Mg/Ca in benthic foraminiferal calcite , 2000, Science.

[30]  Y. Rosenthal,et al.  Temperature and carbonate ion effects on Mg/Ca and Sr/Ca ratios in benthic foraminifera: Aragonitic species Hoeglundina elegans , 2006 .

[31]  Caroline H. Lear,et al.  Rapid stepwise onset of Antarctic glaciation and deeper calcite compensation in the Pacific Ocean , 2005, Nature.