Earth Institute Research Projects

Ocean Acidification: Collaborative Research: Establishing the Magnitude of Sea-Surface Acidification During The Paleocene-Eocene Thermal Maximum

Lead PI: Dr. Baerbel Hoenisch

Unit Affiliation: Geochemistry, Lamont-Doherty Earth Observatory (LDEO)

September 2012 - August 2016
Global ; Pacific Ocean ; Atlantic Ocean ; equatorial Pacific ; South Atlantic
Project Type: Research

DESCRIPTION: The project funded detailed B proxy records for a number of locations across the Pacific and Atlantic to establish regional anomalies in surface ocean carbonate chemistry relative to longer-term trends.

OUTCOMES: The boron isotope data from surface dwelling foraminifera from different ocean settings consistently suggest surface ocean acidification of approximately -0.3 pH units. Extension of the Pacific record into the Paleocene and Eocene corroborates a long-term decrease in surface ocean pH consistent with the long-term warming and d13C trends.


National Science Foundation (NSF)




University of California Santa Cruz, University of Hawaii



Penman, D.E., B. Hönisch, R.E. Zeebe, J.C. Zachos, “Rapid and sustained surface ocean acidification during the Paleocene-Eocene Thermal Maximum”, Paleoceanography 29, doi: 10.1002/2014pa002621.

T.L. Babila, D.E. Penman, B. Hönisch, D. C. Kelly, T. J. Bralower, Y. Rosenthal, J.C. Zachos (2018): Capturing the global signature of surface ocean acidification during the Paleocene-Eocene Thermal Maximum”, Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 376 (2130).


paleocene-eocene thermal maximum carbon dioxide ocean acidification ph ocean and climate physics


Modeling and Adapting to Future Climate