Evaluating Late Pliocene Atlantic Meridional Overturning Circulation dynamics through biogeochemical proxy–model comparison

Abstract. Atlantic Meridional Overturning Circulation (AMOC) is a major feature in the climate system, moving heat and carbon globally. Climate models suggest AMOC’s strength will decrease in the coming decades, with profound implications for regional and global climate patterns. Biogeochemical proxies from benthic foraminifera tests can act as water mass tracers and provide information on deep ocean circulation during past periods of global warmth. The strength of AMOC during the Late Pliocene warm period (∼3.0–3.3 Ma), a pseudo-analogue for future climate change, is poorly constrained, with benthic foraminiferal δ13C showing a spatially expanded North Atlantic Deep Water (NADW), whereas models often simulate a spatially retracted NADW relative to Pre-Industrial. Here we compare δ13C and δ18O proxies in the Atlantic for the warm mid-Piacenzian KM5c interval (3.205 ± 0.02 Ma) with four isotope-enabled climate model simulations allowing for a direct comparison between proxy data and climate models. Proxy data generally show a more expansive NADW with Antarctic Bottom Water limited to the greatest depths. Although climate models resolve key intermediate and deep water masses, differences in spatial patterns between the models are attributed to model parameterisations and boundary conditions. The models and proxy data show different deep ocean structures, which limits our ability to understand deep ocean circulation during the warm mid-Piacenzian KM5c interval and its relevance to future warming scenarios.

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Published
2026-10-30
DOI
https://doi.org/10.5194/egusphere-2026-6464
Primary Topic
Geology and Paleoclimatology Research
Type
preprint

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preprint

Evaluating Late Pliocene Atlantic Meridional Overturning Circulation dynamics through biogeochemical proxy–model comparison

Stijn De Schepper, Friso de Graaf, Deborah N. Tangunan, Natalie Burls et al.
Geology and Paleoclimatology Research
preprint

Evaluating Late Pliocene Atlantic Meridional Overturning Circulation dynamics through biogeochemical proxy–model comparison

Stijn De Schepper, Friso de Graaf, Deborah N. Tangunan, Natalie Burls, Ran Feng, Jordan T. Abell, Cyrus Karas, Erin L. McClymont, Montserrat Alonso‐García, Kate Littler, Melissa A. Berke, Sze Ling Ho, Christian Stepanek, Antje H L Voelker, Benjamin Petrick, Clay Tabor, George E. A. Swann, Julia C. Tindall, Kaustubh Thirumalai, Bjørg Risebrobakken, Yong Sun, Pallavi Anand, Taylor Deneau, Heather L. Ford, Pam Vervoort, Amila Sandaruwan Ratnayake, Anya J. Crocker, Sarah E. Greene, Alan Haywood, Honbing Edmond Duong
preprint en

Abstract

Abstract. Atlantic Meridional Overturning Circulation (AMOC) is a major feature in the climate system, moving heat and carbon globally. Climate models suggest AMOC’s strength will decrease in the coming decades, with profound implications for regional and global climate patterns. Biogeochemical proxies from benthic foraminifera tests can act as water mass tracers and provide information on deep ocean circulation during past periods of global warmth. The strength of AMOC during the Late Pliocene warm period (∼3.0–3.3 Ma), a pseudo-analogue for future climate change, is poorly constrained, with benthic foraminiferal δ13C showing a spatially expanded North Atlantic Deep Water (NADW), whereas models often simulate a spatially retracted NADW relative to Pre-Industrial. Here we compare δ13C and δ18O proxies in the Atlantic for the warm mid-Piacenzian KM5c interval (3.205 ± 0.02 Ma) with four isotope-enabled climate model simulations allowing for a direct comparison between proxy data and climate models. Proxy data generally show a more expansive NADW with Antarctic Bottom Water limited to the greatest depths. Although climate models resolve key intermediate and deep water masses, differences in spatial patterns between the models are attributed to model parameterisations and boundary conditions. The models and proxy data show different deep ocean structures, which limits our ability to understand deep ocean circulation during the warm mid-Piacenzian KM5c interval and its relevance to future warming scenarios.

Universidad de Santiago de Chile (CL), University of Notre Dame (US), Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung (DE), University of Leeds (GB), University of Arizona (US), University of Connecticut (US), University of Nottingham (GB), George Mason University (US), Queen Mary University of London (GB), National Taiwan University (TW), Universidad de Salamanca (ES), Lehigh University (US), Durham University (GB), Chinese Academy of Sciences (CN), The Open University (GB), University of Exeter (GB), Portuguese Sea and Atmosphere Institute (PT), Bjerknes Centre for Climate Research (NO), NORCE Research AS (NO), Institute of Tibetan Plateau Research (CN), Centro de Ciências do Mar do Algarve (PT), University of Bergen (NO), University College London (GB), University of Algarve (PT), Cardiff University (GB), University of Birmingham (GB)
National Science Foundation, Queen Mary University of London, Natural Environment Research Council, HORIZON EUROPE Excellent Science
Life below water, Climate action
Geology and Paleoclimatology Research
DOIOpen Access PDFOpenAlex
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