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Middle Miocene ice sheet dynamics, deep-sea temperatures, and carbon cycling: A Southern Ocean perspective

Shevenell, AE; Kennett, JP; Lea, DW; (2008) Middle Miocene ice sheet dynamics, deep-sea temperatures, and carbon cycling: A Southern Ocean perspective. Geochemistry, Geophysics, Geosystems , 9 , Article Q02006. 10.1029/2007GC001736. Green open access

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Abstract

Relative contributions of ice volume and temperature change to the global similar to 1 parts per thousand delta O-18 increase at similar to 14 Ma are required for understanding feedbacks involved in this major Cenozoic climate transition. A 3-ma benthic foraminifer Mg/Ca record of Southern Ocean temperatures across the middle Miocene climate transition reveals similar to 2 +/- 2 degrees C cooling (14.2-13.8 Ma), indicating that similar to 70% of the increase relates to ice growth. Seawater delta O-18, calculated from Mg/Ca and delta O-18, suggests that at similar to 15 Ma Antarctica's cryosphere entered an interval of apparent eccentricity-paced expansion. Glaciations increased in intensity, revealing a central role for internal climate feedbacks. Comparison of ice volume and ocean temperature records with inferred pCO(2) levels indicates that middle Miocene cryosphere expansion commenced during an interval of Southern Ocean warmth and low atmospheric pCO(2). The Antarctic system appears sensitive to changes in heat/moisture supply when atmospheric pCO(2) was low, suggesting the importance of internal feedbacks in this climate transition.

Type: Article
Title: Middle Miocene ice sheet dynamics, deep-sea temperatures, and carbon cycling: A Southern Ocean perspective
Open access status: An open access version is available from UCL Discovery
DOI: 10.1029/2007GC001736
Publisher version: http://dx.doi.org/10.1029/2007GC001736
Language: English
Additional information: Copyright 2008 by the American Geophysical Union
Keywords: Paleoceanography, Cenozoic climate, Geochemistry, Antarctica, Benthic foraminiferal Mg/Ca, Climate-change, Surface temperature, Dioxide, Evolution, Record, Paleothermometry, Circulation, Glaciation, Hypothesis
UCL classification: UCL > School of BEAMS > Faculty of Maths and Physical Sciences > Earth Sciences
URI: http://discovery.ucl.ac.uk/id/eprint/1302365
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