Middle Miocene Southern Ocean Cooling and Antarctic Cryosphere Expansion

• Published in: Science
• Main Authors: Shevenell, Amelia E., Kennett, James P., Lea, David W.
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Digital Commons @ University of South Florida 2004
• Subjects: Life Sciences; Antarctic; Pacific; Southern Ocean; Antarc*; Planktonic foraminifera
• Online Access: https://digitalcommons.usf.edu/msc_facpub/583; https://doi.org/10.1126/science.1100061

Magnesium/calcium data from Southern Ocean planktonic foraminifera demonstrate that high-latitude (∼55°S) southwest Pacific sea surface temperatures (SSTs) cooled 6° to 7°C during the middle Miocene climate transition (14.2 to 13.8 million years ago). Stepwise surface cooling is paced by eccentricity forcing and precedes Antarctic cryosphere expansion by ∼60 thousand years, suggesting the involvement of additional feedbacks during this interval of inferred low-atmospheric partial pressure of CO2 (pCO2). Comparing SSTs and global carbon cycling proxies challenges the notion that episodic pCO2 drawdown drove this major Cenozoic climate transition. SST, salinity, and ice-volume trends suggest instead that orbitally paced ocean circulation changes altered meridional heat/vapor transport, triggering ice growth and global cooling.