EGU2020-21860, updated on 09 Jan 2023
EGU General Assembly 2020
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

Pacific Meridional Overturning Circulation during the Mid-Pliocene Warm Period

Heather L. Ford1,2, Natalie Burls3, and David Hodell2
Heather L. Ford et al.
  • 1Queen Mary University of London, School of Geography, London, United Kingdom of Great Britain and Northern Ireland (
  • 2Department of Earth Science, University of Cambridge, Cambridge, United Kingdom of Great Britain and Northern Ireland
  • 3Atmospheric, Oceanic, and Earth Sciences, George Mason University, Fairfax, United States of America

Today in the North Pacific only intermediate water forms because of a strong halocline, but Pacific Meridional Overturning Circulation (PMOC) may have existed in the past. The mid-Pliocene warm period (3.264-3.025 Ma) is a time of sustained warmth where atmospheric carbon dioxide concentrations were similar to today and the northern hemisphere was relatively ice free – making it a pseudo-analogue for future climate change. North Pacific sedimentological and climate modeling evidence suggests a PMOC formed during this time.  To determine the spatial extent of a PMOC during the mid-Pliocene warm period, we constructed a depth transect of sites between 2400 to 3400 m water depth on Shatsky Rise by measuring stable isotopes of Cibicidoides wuellerstorfi. We compare these new results with previously published records and calculate anomalies using the OC3 water column and core-top data products. The δ13C spatial pattern is consistent with a modest PMOC of intermediate depth (core ~2000 m) extending to the equator during the mid-Pliocene warm period. Ventilation of the North Pacific by a PMOC has broad implications for deep ocean carbon storage as the North Pacific contains the oldest, carbon-rich waters today. Future work will include minor and trace element analyses to determine the temperature and carbon characteristics of the PMOC water mass and comparisons with PlioMIP modeling outputs.

How to cite: Ford, H. L., Burls, N., and Hodell, D.: Pacific Meridional Overturning Circulation during the Mid-Pliocene Warm Period, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21860,, 2020.