Articles | Volume 21, issue 1
https://doi.org/10.5194/cp-21-79-2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/cp-21-79-2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Research article
| 
14 Jan 2025
Research article |
| 14 Jan 2025
| 14 Jan 2025
Southern Ocean control on atmospheric CO2 changes across late Pliocene Marine Isotope Stage M2
Department of Earth Sciences, Utrecht University, 3584 CB Utrecht, the Netherlands
Leonie Toebrock
Department of Earth Sciences, Utrecht University, 3584 CB Utrecht, the Netherlands
Mart van der Linden
Department of Earth Sciences, Utrecht University, 3584 CB Utrecht, the Netherlands
Fleur Rothstegge
Department of Earth Sciences, Utrecht University, 3584 CB Utrecht, the Netherlands
Martin Ziegler
Department of Earth Sciences, Utrecht University, 3584 CB Utrecht, the Netherlands
Lucas J. Lourens
Department of Earth Sciences, Utrecht University, 3584 CB Utrecht, the Netherlands
Peter K. Bijl
Department of Earth Sciences, Utrecht University, 3584 CB Utrecht, the Netherlands
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Henry Hooghiemstra, Gustavo Sarmiento Pérez, Vladimir Torres Torres, Juan-Carlos Berrío, Lucas Lourens, and Suzette G. A. Flantua
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Peter D. Nooteboom, Peter K. Bijl, Christian Kehl, Erik van Sebille, Martin Ziegler, Anna S. von der Heydt, and Henk A. Dijkstra
Earth Syst. Dynam., 13, 357–371, https://doi.org/10.5194/esd-13-357-2022, https://doi.org/10.5194/esd-13-357-2022, 2022
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Having descended through the water column, microplankton in ocean sediments represents the ocean surface environment and is used as an archive of past and present surface oceanographic conditions. However, this microplankton is advected by turbulent ocean currents during its sinking journey. We use simulations of sinking particles to define ocean bottom provinces and detect these provinces in datasets of sedimentary microplankton, which has implications for palaeoclimate reconstructions.
Peter K. Bijl
Earth Syst. Sci. Data, 14, 579–617, https://doi.org/10.5194/essd-14-579-2022, https://doi.org/10.5194/essd-14-579-2022, 2022
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Using microfossils to gauge the age of rocks and sediments requires an accurate age of their first (origination) and last (extinction) appearances. But how do you know such ages can then be applied worldwide? And what causes regional differences? This paper investigates the regional consistency of ranges of species of a specific microfossil group, organic-walled dinoflagellate cysts. This overview helps in identifying regional differences in the stratigraphic ranges of species and their causes.
Nick Thompson, Ulrich Salzmann, Adrián López-Quirós, Peter K. Bijl, Frida S. Hoem, Johan Etourneau, Marie-Alexandrine Sicre, Sabine Roignant, Emma Hocking, Michael Amoo, and Carlota Escutia
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Peter K. Bijl, Joost Frieling, Marlow Julius Cramwinckel, Christine Boschman, Appy Sluijs, and Francien Peterse
Clim. Past, 17, 2393–2425, https://doi.org/10.5194/cp-17-2393-2021, https://doi.org/10.5194/cp-17-2393-2021, 2021
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Here, we use the latest insights for GDGT and dinocyst-based paleotemperature and paleoenvironmental reconstructions in late Cretaceous–early Oligocene sediments from ODP Site 1172 (East Tasman Plateau, Australia). We reconstruct strong river runoff during the Paleocene–early Eocene, a progressive decline thereafter with increased wet/dry seasonality in the northward-drifting hinterland. Our critical review leaves the anomalous warmth of the Eocene SW Pacific Ocean unexplained.
Frida S. Hoem, Isabel Sauermilch, Suning Hou, Henk Brinkhuis, Francesca Sangiorgi, and Peter K. Bijl
J. Micropalaeontol., 40, 175–193, https://doi.org/10.5194/jm-40-175-2021, https://doi.org/10.5194/jm-40-175-2021, 2021
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We use marine microfossil (dinocyst) assemblage data as well as seismic and tectonic investigations to reconstruct the oceanographic history south of Australia 37–20 Ma as the Tasmanian Gateway widens and deepens. Our results show stable conditions with typically warmer dinocysts south of Australia, which contrasts with the colder dinocysts closer to Antarctica, indicating the establishment of modern oceanographic conditions with a strong Southern Ocean temperature gradient and frontal systems.
Anna Joy Drury, Diederik Liebrand, Thomas Westerhold, Helen M. Beddow, David A. Hodell, Nina Rohlfs, Roy H. Wilkens, Mitchell Lyle, David B. Bell, Dick Kroon, Heiko Pälike, and Lucas J. Lourens
Clim. Past, 17, 2091–2117, https://doi.org/10.5194/cp-17-2091-2021, https://doi.org/10.5194/cp-17-2091-2021, 2021
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We use the first high-resolution southeast Atlantic carbonate record to see how climate dynamics evolved since 30 million years ago (Ma). During ~ 30–13 Ma, eccentricity (orbital circularity) paced carbonate deposition. After the mid-Miocene Climate Transition (~ 14 Ma), precession (Earth's tilt direction) increasingly drove carbonate variability. In the latest Miocene (~ 8 Ma), obliquity (Earth's tilt) pacing appeared, signalling increasing high-latitude influence.
Frida S. Hoem, Luis Valero, Dimitris Evangelinos, Carlota Escutia, Bella Duncan, Robert M. McKay, Henk Brinkhuis, Francesca Sangiorgi, and Peter K. Bijl
Clim. Past, 17, 1423–1442, https://doi.org/10.5194/cp-17-1423-2021, https://doi.org/10.5194/cp-17-1423-2021, 2021
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We present new offshore palaeoceanographic reconstructions for the Oligocene (33.7–24.4 Ma) in the Ross Sea, Antarctica. Our study of dinoflagellate cysts and lipid biomarkers indicates warm-temperate sea surface conditions. We posit that warm surface-ocean conditions near the continental shelf during the Oligocene promoted increased precipitation and heat delivery towards Antarctica that led to dynamic terrestrial ice sheet volumes in the warmer climate state of the Oligocene.
Niels J. de Winter, Tobias Agterhuis, and Martin Ziegler
Clim. Past, 17, 1315–1340, https://doi.org/10.5194/cp-17-1315-2021, https://doi.org/10.5194/cp-17-1315-2021, 2021
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Climate researchers often need to compromise in their sampling between increasing the number of measurements to obtain higher time resolution and combining measurements to improve the reliability of climate reconstructions. In this study, we test several methods for achieving the optimal balance between these competing interests by simulating seasonality reconstructions using stable and clumped isotopes. Our results inform sampling strategies for climate reconstructions in general.
Bas de Boer, Marit Peters, and Lucas J. Lourens
Clim. Past, 17, 331–344, https://doi.org/10.5194/cp-17-331-2021, https://doi.org/10.5194/cp-17-331-2021, 2021
Michiel Baatsen, Anna S. von der Heydt, Matthew Huber, Michael A. Kliphuis, Peter K. Bijl, Appy Sluijs, and Henk A. Dijkstra
Clim. Past, 16, 2573–2597, https://doi.org/10.5194/cp-16-2573-2020, https://doi.org/10.5194/cp-16-2573-2020, 2020
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Warm climates of the deep past have proven to be challenging to reconstruct with the same numerical models used for future predictions. We present results of CESM simulations for the middle to late Eocene (∼ 38 Ma), in which we managed to match the available indications of temperature well. With these results we can now look into regional features and the response to external changes to ultimately better understand the climate when it is in such a warm state.
Marlow Julius Cramwinckel, Lineke Woelders, Emiel P. Huurdeman, Francien Peterse, Stephen J. Gallagher, Jörg Pross, Catherine E. Burgess, Gert-Jan Reichart, Appy Sluijs, and Peter K. Bijl
Clim. Past, 16, 1667–1689, https://doi.org/10.5194/cp-16-1667-2020, https://doi.org/10.5194/cp-16-1667-2020, 2020
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Phases of past transient warming can be used as a test bed to study the environmental response to climate change independent of tectonic change. Using fossil plankton and organic molecules, here we reconstruct surface ocean temperature and circulation in and around the Tasman Gateway during a warming phase 40 million years ago termed the Middle Eocene Climatic Optimum. We find that plankton assemblages track ocean circulation patterns, with superimposed variability being related to temperature.
Emily Dearing Crampton-Flood, Lars J. Noorbergen, Damian Smits, R. Christine Boschman, Timme H. Donders, Dirk K. Munsterman, Johan ten Veen, Francien Peterse, Lucas Lourens, and Jaap S. Sinninghe Damsté
Clim. Past, 16, 523–541, https://doi.org/10.5194/cp-16-523-2020, https://doi.org/10.5194/cp-16-523-2020, 2020
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The mid-Pliocene warm period (mPWP; 3.3–3.0 million years ago) is thought to be the last geological interval with similar atmospheric carbon dioxide concentrations as the present day. Further, the mPWP was 2–3 °C warmer than present, making it a good analogue for estimating the effects of future climate change. Here, we construct a new precise age model for the North Sea during the mPWP, and provide a detailed reconstruction of terrestrial and marine climate using a multi-proxy approach.
Christopher J. Hollis, Tom Dunkley Jones, Eleni Anagnostou, Peter K. Bijl, Marlow Julius Cramwinckel, Ying Cui, Gerald R. Dickens, Kirsty M. Edgar, Yvette Eley, David Evans, Gavin L. Foster, Joost Frieling, Gordon N. Inglis, Elizabeth M. Kennedy, Reinhard Kozdon, Vittoria Lauretano, Caroline H. Lear, Kate Littler, Lucas Lourens, A. Nele Meckler, B. David A. Naafs, Heiko Pälike, Richard D. Pancost, Paul N. Pearson, Ursula Röhl, Dana L. Royer, Ulrich Salzmann, Brian A. Schubert, Hannu Seebeck, Appy Sluijs, Robert P. Speijer, Peter Stassen, Jessica Tierney, Aradhna Tripati, Bridget Wade, Thomas Westerhold, Caitlyn Witkowski, James C. Zachos, Yi Ge Zhang, Matthew Huber, and Daniel J. Lunt
Geosci. Model Dev., 12, 3149–3206, https://doi.org/10.5194/gmd-12-3149-2019, https://doi.org/10.5194/gmd-12-3149-2019, 2019
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The Deep-Time Model Intercomparison Project (DeepMIP) is a model–data intercomparison of the early Eocene (around 55 million years ago), the last time that Earth's atmospheric CO2 concentrations exceeded 1000 ppm. Previously, we outlined the experimental design for climate model simulations. Here, we outline the methods used for compilation and analysis of climate proxy data. The resulting climate
atlaswill provide insights into the mechanisms that control past warm climate states.
Robert McKay, Neville Exon, Dietmar Müller, Karsten Gohl, Michael Gurnis, Amelia Shevenell, Stuart Henrys, Fumio Inagaki, Dhananjai Pandey, Jessica Whiteside, Tina van de Flierdt, Tim Naish, Verena Heuer, Yuki Morono, Millard Coffin, Marguerite Godard, Laura Wallace, Shuichi Kodaira, Peter Bijl, Julien Collot, Gerald Dickens, Brandon Dugan, Ann G. Dunlea, Ron Hackney, Minoru Ikehara, Martin Jutzeler, Lisa McNeill, Sushant Naik, Taryn Noble, Bradley Opdyke, Ingo Pecher, Lowell Stott, Gabriele Uenzelmann-Neben, Yatheesh Vadakkeykath, and Ulrich G. Wortmann
Sci. Dril., 24, 61–70, https://doi.org/10.5194/sd-24-61-2018, https://doi.org/10.5194/sd-24-61-2018, 2018
Julian D. Hartman, Peter K. Bijl, and Francesca Sangiorgi
J. Micropalaeontol., 37, 445–497, https://doi.org/10.5194/jm-37-445-2018, https://doi.org/10.5194/jm-37-445-2018, 2018
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We present an extensive overview of the organic microfossil remains found at Site U1357, Adélie Basin, East Antarctica. The organic microfossil remains are exceptionally well preserved and are derived from unicellular as well as higher organisms. We provide a morphological description, photographic images, and a discussion of the ecological preferences of the biological species from which the organic remains were derived.
Julian D. Hartman, Francesca Sangiorgi, Ariadna Salabarnada, Francien Peterse, Alexander J. P. Houben, Stefan Schouten, Henk Brinkhuis, Carlota Escutia, and Peter K. Bijl
Clim. Past, 14, 1275–1297, https://doi.org/10.5194/cp-14-1275-2018, https://doi.org/10.5194/cp-14-1275-2018, 2018
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We reconstructed sea surface temperatures for the Oligocene and Miocene periods (34–11 Ma) based on archaeal lipids from a site close to the Wilkes Land coast, Antarctica. Our record suggests generally warm to temperate surface waters: on average 17 °C. Based on the lithology, glacial and interglacial temperatures could be distinguished, showing an average 3 °C offset. The long-term temperature trend resembles the benthic δ18O stack, which may have implications for ice volume reconstructions.
Peter K. Bijl, Alexander J. P. Houben, Julian D. Hartman, Jörg Pross, Ariadna Salabarnada, Carlota Escutia, and Francesca Sangiorgi
Clim. Past, 14, 1015–1033, https://doi.org/10.5194/cp-14-1015-2018, https://doi.org/10.5194/cp-14-1015-2018, 2018
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We document Southern Ocean surface ocean conditions and changes therein during the Oligocene and Miocene (34–10 Myr ago). We infer profound long-term and short-term changes in ice-proximal oceanographic conditions: sea surface temperature, nutrient conditions and sea ice. Our results point to warm-temperate, oligotrophic, ice-proximal oceanographic conditions. These distinct oceanographic conditions may explain the high amplitude in inferred Oligocene–Miocene Antarctic ice volume changes.
Ariadna Salabarnada, Carlota Escutia, Ursula Röhl, C. Hans Nelson, Robert McKay, Francisco J. Jiménez-Espejo, Peter K. Bijl, Julian D. Hartman, Stephanie L. Strother, Ulrich Salzmann, Dimitris Evangelinos, Adrián López-Quirós, José Abel Flores, Francesca Sangiorgi, Minoru Ikehara, and Henk Brinkhuis
Clim. Past, 14, 991–1014, https://doi.org/10.5194/cp-14-991-2018, https://doi.org/10.5194/cp-14-991-2018, 2018
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Here we reconstruct ice sheet and paleoceanographic configurations in the East Antarctic Wilkes Land margin based on a multi-proxy study conducted in late Oligocene (26–25 Ma) sediments from IODP Site U1356. The new obliquity-forced glacial–interglacial sedimentary model shows that, under the high CO2 values of the late Oligocene, ice sheets had mostly retreated to their terrestrial margins and the ocean was very dynamic with shifting positions of the polar fronts and associated water masses.
Michiel Baatsen, Anna S. von der Heydt, Matthew Huber, Michael A. Kliphuis, Peter K. Bijl, Appy Sluijs, and Henk A. Dijkstra
Clim. Past Discuss., https://doi.org/10.5194/cp-2018-43, https://doi.org/10.5194/cp-2018-43, 2018
Revised manuscript not accepted
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The Eocene marks a period where the climate was in a hothouse state, without any continental-scale ice sheets. Such climates have proven difficult to reproduce in models, especially their low temperature difference between equator and poles. Here, we present high resolution CESM simulations using a new geographic reconstruction of the middle-to-late Eocene. The results provide new insights into a period for which knowledge is limited, leading up to a transition into the present icehouse state.
Timme H. Donders, Niels A. G. M. van Helmond, Roel Verreussel, Dirk Munsterman, Johan ten Veen, Robert P. Speijer, Johan W. H. Weijers, Francesca Sangiorgi, Francien Peterse, Gert-Jan Reichart, Jaap S. Sinninghe Damsté, Lucas Lourens, Gesa Kuhlmann, and Henk Brinkhuis
Clim. Past, 14, 397–411, https://doi.org/10.5194/cp-14-397-2018, https://doi.org/10.5194/cp-14-397-2018, 2018
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The buildup and melting of ice during the early glaciations in the Northern Hemisphere, around 2.5 million years ago, were far shorter in duration than during the last million years. Based on molecular compounds and microfossils from sediments dating back to the early glaciations we show that the temperature on land and in the sea changed simultaneously and was a major factor in the ice buildup in the Northern Hemisphere. These data provide key insights into the dynamics of early glaciations.
Helen M. Beddow, Diederik Liebrand, Douglas S. Wilson, Frits J. Hilgen, Appy Sluijs, Bridget S. Wade, and Lucas J. Lourens
Clim. Past, 14, 255–270, https://doi.org/10.5194/cp-14-255-2018, https://doi.org/10.5194/cp-14-255-2018, 2018
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We present two astronomy-based timescales for climate records from the Pacific Ocean. These records range from 24 to 22 million years ago, a time period when Earth was warmer than today and the only land ice was located on Antarctica. We use tectonic plate-pair spreading rates to test the two timescales, which shows that the carbonate record yields the best timescale. In turn, this implies that Earth’s climate system and carbon cycle responded slowly to changes in incoming solar radiation.
Joost Frieling, Emiel P. Huurdeman, Charlotte C. M. Rem, Timme H. Donders, Jörg Pross, Steven M. Bohaty, Guy R. Holdgate, Stephen J. Gallagher, Brian McGowran, and Peter K. Bijl
J. Micropalaeontol., 37, 317–339, https://doi.org/10.5194/jm-37-317-2018, https://doi.org/10.5194/jm-37-317-2018, 2018
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The hothouse climate of the early Paleogene and the associated violent carbon cycle perturbations are of particular interest to understanding current and future global climate change. Using dinoflagellate cysts and stable carbon isotope analyses, we identify several significant events, e.g., the Paleocene–Eocene Thermal Maximum in sedimentary deposits from the Otway Basin, SE Australia. We anticipate that this study will facilitate detailed climate reconstructions west of the Tasmanian Gateway.
Peter K. Bijl, Alexander J. P. Houben, Anja Bruls, Jörg Pross, and Francesca Sangiorgi
J. Micropalaeontol., 37, 105–138, https://doi.org/10.5194/jm-37-105-2018, https://doi.org/10.5194/jm-37-105-2018, 2018
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In order to use ocean sediments as a recorder of past oceanographic changes, a critical first step is to stratigraphically date the sediments. The absence of microfossils with known stratigraphic ranges has always hindered dating of Southern Ocean sediments. Here we tie dinocyst ranges to the international timescale in a well-dated sediment core from offshore Antarctica. With this, we can now use dinocysts as a biostratigraphic tool in otherwise stratigraphically poorly dated sediments.
Lennert B. Stap, Roderik S. W. van de Wal, Bas de Boer, Richard Bintanja, and Lucas J. Lourens
Clim. Past, 13, 1243–1257, https://doi.org/10.5194/cp-13-1243-2017, https://doi.org/10.5194/cp-13-1243-2017, 2017
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We show the results of transient simulations with a coupled climate–ice sheet model over the past 38 million years. The CO2 forcing of the model is inversely obtained from a benthic δ18O stack. These simulations enable us to study the influence of ice sheet variability on climate change on long timescales. We find that ice sheet–climate interaction strongly enhances Earth system sensitivity and polar amplification.
Stefanie Kaboth, Patrick Grunert, and Lucas Lourens
Clim. Past, 13, 1023–1035, https://doi.org/10.5194/cp-13-1023-2017, https://doi.org/10.5194/cp-13-1023-2017, 2017
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This study is devoted to reconstructing Mediterranean Outflow Water (MOW) variability and the interplay between the Mediterranean and North Atlantic climate systems during the Early Pleistocene. We find indication that the increasing production of MOW aligns with the intensification of the North Atlantic overturning circulation, highlighting the potential of MOW to modulate the North Atlantic salt budget. Our results are based on new stable isotope and grain-size data from IODP 339 Site U1389.
Stephanie L. Strother, Ulrich Salzmann, Francesca Sangiorgi, Peter K. Bijl, Jörg Pross, Carlota Escutia, Ariadna Salabarnada, Matthew J. Pound, Jochen Voss, and John Woodward
Biogeosciences, 14, 2089–2100, https://doi.org/10.5194/bg-14-2089-2017, https://doi.org/10.5194/bg-14-2089-2017, 2017
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One of the main challenges in Antarctic vegetation reconstructions is the uncertainty in unambiguously identifying reworked pollen and spore assemblages in marine sedimentary records influenced by waxing and waning ice sheets. This study uses red fluorescence and digital imaging as a new tool to identify reworking in a marine sediment core from circum-Antarctic waters to reconstruct Cenozoic climate change and vegetation with high confidence.
Michiel Baatsen, Douwe J. J. van Hinsbergen, Anna S. von der Heydt, Henk A. Dijkstra, Appy Sluijs, Hemmo A. Abels, and Peter K. Bijl
Clim. Past, 12, 1635–1644, https://doi.org/10.5194/cp-12-1635-2016, https://doi.org/10.5194/cp-12-1635-2016, 2016
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One of the major difficulties in modelling palaeoclimate is constricting the boundary conditions, causing significant discrepancies between different studies. Here, a new method is presented to automate much of the process of generating the necessary geographical reconstructions. The latter can be made using various rotational frameworks and topography/bathymetry input, allowing for easy inter-comparisons and the incorporation of the latest insights from geoscientific research.
Hemmo A. Abels, Vittoria Lauretano, Anna E. van Yperen, Tarek Hopman, James C. Zachos, Lucas J. Lourens, Philip D. Gingerich, and Gabriel J. Bowen
Clim. Past, 12, 1151–1163, https://doi.org/10.5194/cp-12-1151-2016, https://doi.org/10.5194/cp-12-1151-2016, 2016
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Ancient greenhouse warming episodes are studied in river floodplain sediments in the western interior of the USA. Paleohydrological changes of four smaller warming episodes are revealed to be the opposite of those of the largest, most-studied event. Carbon cycle tracers are used to ascertain whether the largest event was a similar event but proportional to the smaller ones or whether this event was distinct in size as well as in carbon sourcing, a question the current work cannot answer.
Willem P. Sijp, Anna S. von der Heydt, and Peter K. Bijl
Clim. Past, 12, 807–817, https://doi.org/10.5194/cp-12-807-2016, https://doi.org/10.5194/cp-12-807-2016, 2016
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The timing and role in ocean circulation and climate of the opening of Southern Ocean gateways is as yet elusive. Here, we present the first model results specific to the early-to-middle Eocene where, in agreement with the field evidence, a southerly shallow opening of the Tasman Gateway does indeed cause a westward flow across the Tasman Gateway, in agreement with recent micropalaeontological studies.
J. H. C. Bosmans, F. J. Hilgen, E. Tuenter, and L. J. Lourens
Clim. Past, 11, 1335–1346, https://doi.org/10.5194/cp-11-1335-2015, https://doi.org/10.5194/cp-11-1335-2015, 2015
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Our study shows that the influence of obliquity (the tilt of Earth's rotational axis) can be explained through changes in the insolation gradient across the tropics. This explanation is fundamentally different from high-latitude mechanisms that were previously often inferred to explain obliquity signals in low-latitude paleoclimate records, for instance glacial fluctuations. Our study is based on state-of-the-art climate model experiments.
V. Lauretano, K. Littler, M. Polling, J. C. Zachos, and L. J. Lourens
Clim. Past, 11, 1313–1324, https://doi.org/10.5194/cp-11-1313-2015, https://doi.org/10.5194/cp-11-1313-2015, 2015
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Several episodes of global warming took place during greenhouse conditions in the early Eocene and are recorded in deep-sea sediments. The stable carbon and oxygen isotope records are used to investigate the magnitude of six of these events describing their effects on the global carbon cycle and the associated temperature response. Findings indicate that these events share a common nature and hint to the presence of multiple sources of carbon release.
B. S. Slotnick, V. Lauretano, J. Backman, G. R. Dickens, A. Sluijs, and L. Lourens
Clim. Past, 11, 473–493, https://doi.org/10.5194/cp-11-473-2015, https://doi.org/10.5194/cp-11-473-2015, 2015
L. B. Stap, R. S. W. van de Wal, B. de Boer, R. Bintanja, and L. J. Lourens
Clim. Past, 10, 2135–2152, https://doi.org/10.5194/cp-10-2135-2014, https://doi.org/10.5194/cp-10-2135-2014, 2014
L. Contreras, J. Pross, P. K. Bijl, R. B. O'Hara, J. I. Raine, A. Sluijs, and H. Brinkhuis
Clim. Past, 10, 1401–1420, https://doi.org/10.5194/cp-10-1401-2014, https://doi.org/10.5194/cp-10-1401-2014, 2014
D. A. Hodell, L. Lourens, D. A. V. Stow, J. Hernández-Molina, C. A. Alvarez Zarikian, and the Shackleton Site Project Members
Sci. Dril., 16, 13–19, https://doi.org/10.5194/sd-16-13-2013, https://doi.org/10.5194/sd-16-13-2013, 2013
R. S. W. van de Wal, B. de Boer, L. J. Lourens, P. Köhler, and R. Bintanja
Clim. Past, 7, 1459–1469, https://doi.org/10.5194/cp-7-1459-2011, https://doi.org/10.5194/cp-7-1459-2011, 2011
D. Liebrand, L. J. Lourens, D. A. Hodell, B. de Boer, R. S. W. van de Wal, and H. Pälike
Clim. Past, 7, 869–880, https://doi.org/10.5194/cp-7-869-2011, https://doi.org/10.5194/cp-7-869-2011, 2011
Related subject area
Subject: Proxy Use-Development-Validation | Archive: Marine Archives | Timescale: Cenozoic
A clumped isotope calibration of coccoliths at well-constrained culture temperatures for marine temperature reconstructions
Can we reliably reconstruct the mid-Pliocene Warm Period with sparse data and uncertain models?
Paleocene–Eocene age glendonites from the Mid-Norwegian Margin – indicators of cold snaps in the hothouse?
Assessing environmental change associated with early Eocene hyperthermals in the Atlantic Coastal Plain, USA
Technical note: A new online tool for δ18O–temperature conversions
A 15-million-year surface- and subsurface-integrated TEX86 temperature record from the eastern equatorial Atlantic
Sclerochronological evidence of pronounced seasonality from the late Pliocene of the southern North Sea basin and its implications
Pliocene evolution of the tropical Atlantic thermocline depth
Maastrichtian–Rupelian paleoclimates in the southwest Pacific – a critical re-evaluation of biomarker paleothermometry and dinoflagellate cyst paleoecology at Ocean Drilling Program Site 1172
Southern Ocean bottom-water cooling and ice sheet expansion during the middle Miocene climate transition
Rapid and sustained environmental responses to global warming: the Paleocene–Eocene Thermal Maximum in the eastern North Sea
Atmospheric carbon dioxide variations across the middle Miocene climate transition
OPTiMAL: a new machine learning approach for GDGT-based palaeothermometry
Technical note: A new automated radiolarian image acquisition, stacking, processing, segmentation and identification workflow
Late Paleocene–early Eocene Arctic Ocean sea surface temperatures: reassessing biomarker paleothermometry at Lomonosov Ridge
Surface-circulation change in the southwest Pacific Ocean across the Middle Eocene Climatic Optimum: inferences from dinoflagellate cysts and biomarker paleothermometry
A new age model for the Pliocene of the southern North Sea basin: a multi-proxy climate reconstruction
Joint inversion of proxy system models to reconstruct paleoenvironmental time series from heterogeneous data
Mercury anomalies across the Palaeocene–Eocene Thermal Maximum
Reinforcing the North Atlantic backbone: revision and extension of the composite splice at ODP Site 982
Highly variable Pliocene sea surface conditions in the Norwegian Sea
The PRISM4 (mid-Piacenzian) paleoenvironmental reconstruction
Revisiting carbonate chemistry controls on planktic foraminifera Mg / Ca: implications for sea surface temperature and hydrology shifts over the Paleocene–Eocene Thermal Maximum and Eocene–Oligocene transition
The Paleocene–Eocene Thermal Maximum at DSDP Site 277, Campbell Plateau, southern Pacific Ocean
The bivalve Glycymeris planicostalis as a high-resolution paleoclimate archive for the Rupelian (Early Oligocene) of central Europe
Pliocene diatom and sponge spicule oxygen isotope ratios from the Bering Sea: isotopic offsets and future directions
Re-evaluation of the age model for North Atlantic Ocean Site 982 – arguments for a return to the original chronology
Exploring the controls on element ratios in middle Eocene samples of the benthic foraminifera Oridorsalis umbonatus
Application of Fourier Transform Infrared Spectroscopy (FTIR) for assessing biogenic silica sample purity in geochemical analyses and palaeoenvironmental research
Alexander J. Clark, Ismael Torres-Romero, Madalina Jaggi, Stefano M. Bernasconi, and Heather M. Stoll
Clim. Past, 20, 2081–2101, https://doi.org/10.5194/cp-20-2081-2024, https://doi.org/10.5194/cp-20-2081-2024, 2024
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Coccoliths are abundant in sediments across the world’s oceans, yet it is difficult to apply traditional carbon or oxygen isotope methodologies for temperature reconstructions. We show that our coccolith clumped isotope temperature calibration with well-constrained temperatures systematically differs from inorganic carbonate calibrations. We suggest the use of our well-constrained calibration for future coccolith carbonate temperature reconstructions.
James D. Annan, Julia C. Hargreaves, Thorsten Mauritsen, Erin McClymont, and Sze Ling Ho
Clim. Past, 20, 1989–1999, https://doi.org/10.5194/cp-20-1989-2024, https://doi.org/10.5194/cp-20-1989-2024, 2024
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We have created a new global surface temperature reconstruction of the climate of the mid-Pliocene Warm Period, representing the period roughly 3.2 million years before the present day. We estimate that the globally averaged mean temperature was around 3.9 °C warmer than it was in pre-industrial times, but there is significant uncertainty in this value.
Madeleine L. Vickers, Morgan T. Jones, Jack Longman, David Evans, Clemens V. Ullmann, Ella Wulfsberg Stokke, Martin Vickers, Joost Frieling, Dustin T. Harper, Vincent J. Clementi, and IODP Expedition 396 Scientists
Clim. Past, 20, 1–23, https://doi.org/10.5194/cp-20-1-2024, https://doi.org/10.5194/cp-20-1-2024, 2024
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The discovery of cold-water glendonite pseudomorphs in sediments deposited during the hottest part of the Cenozoic poses an apparent climate paradox. This study examines their occurrence, association with volcanic sediments, and speculates on the timing and extent of cooling, fitting this with current understanding of global climate during this period. We propose that volcanic activity was key to both physical and chemical conditions that enabled the formation of glendonites in these sediments.
William Rush, Jean Self-Trail, Yang Zhang, Appy Sluijs, Henk Brinkhuis, James Zachos, James G. Ogg, and Marci Robinson
Clim. Past, 19, 1677–1698, https://doi.org/10.5194/cp-19-1677-2023, https://doi.org/10.5194/cp-19-1677-2023, 2023
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The Eocene contains several brief warming periods referred to as hyperthermals. Studying these events and how they varied between locations can help provide insight into our future warmer world. This study provides a characterization of two of these events in the mid-Atlantic region of the USA. The records of climate that we measured demonstrate significant changes during this time period, but the type and timing of these changes highlight the complexity of climatic changes.
Daniel E. Gaskell and Pincelli M. Hull
Clim. Past, 19, 1265–1274, https://doi.org/10.5194/cp-19-1265-2023, https://doi.org/10.5194/cp-19-1265-2023, 2023
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One of the most common ways of reconstructing temperatures in the geologic past is by analyzing oxygen isotope ratios in fossil shells. However, converting these data to temperatures can be a technically complicated task. Here, we present a new online tool that automates this task.
Carolien M. H. van der Weijst, Koen J. van der Laan, Francien Peterse, Gert-Jan Reichart, Francesca Sangiorgi, Stefan Schouten, Tjerk J. T. Veenstra, and Appy Sluijs
Clim. Past, 18, 1947–1962, https://doi.org/10.5194/cp-18-1947-2022, https://doi.org/10.5194/cp-18-1947-2022, 2022
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The TEX86 proxy is often used by paleoceanographers to reconstruct past sea-surface temperatures. However, the origin of the TEX86 signal in marine sediments has been debated since the proxy was first proposed. In our paper, we show that TEX86 carries a mixed sea-surface and subsurface temperature signal and should be calibrated accordingly. Using our 15-million-year record, we subsequently show how a TEX86 subsurface temperature record can be used to inform us on past sea-surface temperatures.
Andrew L. A. Johnson, Annemarie M. Valentine, Bernd R. Schöne, Melanie J. Leng, and Stijn Goolaerts
Clim. Past, 18, 1203–1229, https://doi.org/10.5194/cp-18-1203-2022, https://doi.org/10.5194/cp-18-1203-2022, 2022
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Determining seasonal temperatures demands proxies that record the highest and lowest temperatures over the annual cycle. Many record neither, but oxygen isotope profiles from shells in principle record both. Oxygen isotope data from late Pliocene bivalve molluscs of the southern North Sea basin show that the seasonal temperature range was at times much higher than previously estimated and higher than now. This suggests reduced oceanic heat supply, in contrast to some previous interpretations.
Carolien M. H. van der Weijst, Josse Winkelhorst, Wesley de Nooijer, Anna von der Heydt, Gert-Jan Reichart, Francesca Sangiorgi, and Appy Sluijs
Clim. Past, 18, 961–973, https://doi.org/10.5194/cp-18-961-2022, https://doi.org/10.5194/cp-18-961-2022, 2022
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A hypothesized link between Pliocene (5.3–2.5 million years ago) global climate and tropical thermocline depth is currently only backed up by data from the Pacific Ocean. In our paper, we present temperature, salinity, and thermocline records from the tropical Atlantic Ocean. Surprisingly, the Pliocene thermocline evolution was remarkably different in the Atlantic and Pacific. We need to reevaluate the mechanisms that drive thermocline depth, and how these are tied to global climate change.
Peter K. Bijl, Joost Frieling, Marlow Julius Cramwinckel, Christine Boschman, Appy Sluijs, and Francien Peterse
Clim. Past, 17, 2393–2425, https://doi.org/10.5194/cp-17-2393-2021, https://doi.org/10.5194/cp-17-2393-2021, 2021
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Here, we use the latest insights for GDGT and dinocyst-based paleotemperature and paleoenvironmental reconstructions in late Cretaceous–early Oligocene sediments from ODP Site 1172 (East Tasman Plateau, Australia). We reconstruct strong river runoff during the Paleocene–early Eocene, a progressive decline thereafter with increased wet/dry seasonality in the northward-drifting hinterland. Our critical review leaves the anomalous warmth of the Eocene SW Pacific Ocean unexplained.
Thomas J. Leutert, Sevasti Modestou, Stefano M. Bernasconi, and A. Nele Meckler
Clim. Past, 17, 2255–2271, https://doi.org/10.5194/cp-17-2255-2021, https://doi.org/10.5194/cp-17-2255-2021, 2021
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The Miocene climatic optimum associated with high atmospheric CO2 levels (~17–14 Ma) was followed by a period of dramatic climate change. We present a clumped isotope-based bottom-water temperature record from the Southern Ocean covering this key climate transition. Our record reveals warm conditions and a substantial cooling preceding the main ice volume increase, possibly caused by thresholds involved in ice growth and/or regional effects at our study site.
Ella W. Stokke, Morgan T. Jones, Lars Riber, Haflidi Haflidason, Ivar Midtkandal, Bo Pagh Schultz, and Henrik H. Svensen
Clim. Past, 17, 1989–2013, https://doi.org/10.5194/cp-17-1989-2021, https://doi.org/10.5194/cp-17-1989-2021, 2021
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In this paper, we present new sedimentological, geochemical, and mineralogical data exploring the environmental response to climatic and volcanic impact during the Paleocene–Eocene Thermal Maximum (~55.9 Ma; PETM). Our data suggest a rise in continental weathering and a shift to anoxic–sulfidic conditions. This indicates a rapid environmental response to changes in the carbon cycle and temperatures and highlights the important role of shelf areas as carbon sinks driving the PETM recovery.
Markus Raitzsch, Jelle Bijma, Torsten Bickert, Michael Schulz, Ann Holbourn, and Michal Kučera
Clim. Past, 17, 703–719, https://doi.org/10.5194/cp-17-703-2021, https://doi.org/10.5194/cp-17-703-2021, 2021
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At approximately 14 Ma, the East Antarctic Ice Sheet expanded to almost its current extent, but the role of CO2 in this major climate transition is not entirely known. We show that atmospheric CO2 might have varied on 400 kyr cycles linked to the eccentricity of the Earth’s orbit. The resulting change in weathering and ocean carbon cycle affected atmospheric CO2 in a way that CO2 rose after Antarctica glaciated, helping to stabilize the climate system on its way to the “ice-house” world.
Tom Dunkley Jones, Yvette L. Eley, William Thomson, Sarah E. Greene, Ilya Mandel, Kirsty Edgar, and James A. Bendle
Clim. Past, 16, 2599–2617, https://doi.org/10.5194/cp-16-2599-2020, https://doi.org/10.5194/cp-16-2599-2020, 2020
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We explore the utiliity of the composition of fossil lipid biomarkers, which are commonly preserved in ancient marine sediments, in providing estimates of past ocean temperatures. The group of lipids concerned show compositional changes across the modern oceans that are correlated, to some extent, with local surface ocean temperatures. Here we present new machine learning approaches to improve our understanding of this temperature sensitivity and its application to reconstructing past climates.
Martin Tetard, Ross Marchant, Giuseppe Cortese, Yves Gally, Thibault de Garidel-Thoron, and Luc Beaufort
Clim. Past, 16, 2415–2429, https://doi.org/10.5194/cp-16-2415-2020, https://doi.org/10.5194/cp-16-2415-2020, 2020
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Radiolarians are marine micro-organisms that produce a siliceous shell that is preserved in the fossil record and can be used to reconstruct past climate variability. However, their study is only possible after a time-consuming manual selection of their shells from the sediment followed by their individual identification. Thus, we develop a new fully automated workflow consisting of microscopic radiolarian image acquisition, image processing and identification using artificial intelligence.
Appy Sluijs, Joost Frieling, Gordon N. Inglis, Klaas G. J. Nierop, Francien Peterse, Francesca Sangiorgi, and Stefan Schouten
Clim. Past, 16, 2381–2400, https://doi.org/10.5194/cp-16-2381-2020, https://doi.org/10.5194/cp-16-2381-2020, 2020
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We revisit 15-year-old reconstructions of sea surface temperatures in the Arctic Ocean for the late Paleocene and early Eocene epochs (∼ 57–53 million years ago) based on the distribution of fossil membrane lipids of archaea preserved in Arctic Ocean sediments. We find that improvements in the methods over the past 15 years do not lead to different results. However, data quality is now higher and potential biases better characterized. Results confirm remarkable Arctic warmth during this time.
Marlow Julius Cramwinckel, Lineke Woelders, Emiel P. Huurdeman, Francien Peterse, Stephen J. Gallagher, Jörg Pross, Catherine E. Burgess, Gert-Jan Reichart, Appy Sluijs, and Peter K. Bijl
Clim. Past, 16, 1667–1689, https://doi.org/10.5194/cp-16-1667-2020, https://doi.org/10.5194/cp-16-1667-2020, 2020
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Phases of past transient warming can be used as a test bed to study the environmental response to climate change independent of tectonic change. Using fossil plankton and organic molecules, here we reconstruct surface ocean temperature and circulation in and around the Tasman Gateway during a warming phase 40 million years ago termed the Middle Eocene Climatic Optimum. We find that plankton assemblages track ocean circulation patterns, with superimposed variability being related to temperature.
Emily Dearing Crampton-Flood, Lars J. Noorbergen, Damian Smits, R. Christine Boschman, Timme H. Donders, Dirk K. Munsterman, Johan ten Veen, Francien Peterse, Lucas Lourens, and Jaap S. Sinninghe Damsté
Clim. Past, 16, 523–541, https://doi.org/10.5194/cp-16-523-2020, https://doi.org/10.5194/cp-16-523-2020, 2020
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The mid-Pliocene warm period (mPWP; 3.3–3.0 million years ago) is thought to be the last geological interval with similar atmospheric carbon dioxide concentrations as the present day. Further, the mPWP was 2–3 °C warmer than present, making it a good analogue for estimating the effects of future climate change. Here, we construct a new precise age model for the North Sea during the mPWP, and provide a detailed reconstruction of terrestrial and marine climate using a multi-proxy approach.
Gabriel J. Bowen, Brenden Fischer-Femal, Gert-Jan Reichart, Appy Sluijs, and Caroline H. Lear
Clim. Past, 16, 65–78, https://doi.org/10.5194/cp-16-65-2020, https://doi.org/10.5194/cp-16-65-2020, 2020
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Past climate conditions are reconstructed using indirect and incomplete geological, biological, and geochemical proxy data. We propose that such reconstructions are best obtained by statistical inversion of hierarchical models that represent how multi–proxy observations and calibration data are produced by variation of environmental conditions in time and/or space. These methods extract new information from traditional proxies and provide robust, comprehensive estimates of uncertainty.
Morgan T. Jones, Lawrence M. E. Percival, Ella W. Stokke, Joost Frieling, Tamsin A. Mather, Lars Riber, Brian A. Schubert, Bo Schultz, Christian Tegner, Sverre Planke, and Henrik H. Svensen
Clim. Past, 15, 217–236, https://doi.org/10.5194/cp-15-217-2019, https://doi.org/10.5194/cp-15-217-2019, 2019
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Mercury anomalies in sedimentary rocks are used to assess whether there were periods of elevated volcanism in the geological record. We focus on five sites that cover the Palaeocene–Eocene Thermal Maximum, an extreme global warming event that occurred 55.8 million years ago. We find that sites close to the eruptions from the North Atlantic Igneous Province display significant mercury anomalies across this time interval, suggesting that magmatism played a role in the global warming event.
Anna Joy Drury, Thomas Westerhold, David Hodell, and Ursula Röhl
Clim. Past, 14, 321–338, https://doi.org/10.5194/cp-14-321-2018, https://doi.org/10.5194/cp-14-321-2018, 2018
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North Atlantic Site 982 is key to our understanding of climate evolution over the past 12 million years. However, the stratigraphy and age model are unverified. We verify the composite splice using XRF core scanning data and establish a revised benthic foraminiferal stable isotope astrochronology from 8.0–4.5 million years ago. Our new stratigraphy accurately correlates the Atlantic and the Mediterranean and suggests a connection between late Miocene cooling and dynamic ice sheet expansion.
Paul E. Bachem, Bjørg Risebrobakken, Stijn De Schepper, and Erin L. McClymont
Clim. Past, 13, 1153–1168, https://doi.org/10.5194/cp-13-1153-2017, https://doi.org/10.5194/cp-13-1153-2017, 2017
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We present a high-resolution multi-proxy study of the Norwegian Sea, covering the 5.33 to 3.14 Ma time window within the Pliocene. We show that large-scale climate transitions took place during this warmer than modern time, most likely in response to ocean gateway transformations. Strong warming at 4.0 Ma in the Norwegian Sea, when regions closer to Greenland cooled, indicate that increased northward ocean heat transport may be compatible with expanding glaciation and Arctic sea ice growth.
Harry Dowsett, Aisling Dolan, David Rowley, Robert Moucha, Alessandro M. Forte, Jerry X. Mitrovica, Matthew Pound, Ulrich Salzmann, Marci Robinson, Mark Chandler, Kevin Foley, and Alan Haywood
Clim. Past, 12, 1519–1538, https://doi.org/10.5194/cp-12-1519-2016, https://doi.org/10.5194/cp-12-1519-2016, 2016
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Past intervals in Earth history provide unique windows into conditions much different than those observed today. We investigated the paleoenvironments of a past warm interval (~ 3 million years ago). Our reconstruction includes data sets for surface temperature, vegetation, soils, lakes, ice sheets, topography, and bathymetry. These data are being used along with global climate models to expand our understanding of the climate system and to help us prepare for future changes.
David Evans, Bridget S. Wade, Michael Henehan, Jonathan Erez, and Wolfgang Müller
Clim. Past, 12, 819–835, https://doi.org/10.5194/cp-12-819-2016, https://doi.org/10.5194/cp-12-819-2016, 2016
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We show that seawater pH exerts a substantial control on planktic foraminifera Mg / Ca, a widely applied palaeothermometer. As a result, temperature reconstructions based on this proxy are likely inaccurate over climatic events associated with a significant change in pH. We examine the implications of our findings for hydrological and temperature shifts over the Paleocene-Eocene Thermal Maximum and for the degree of surface ocean precursor cooling before the Eocene-Oligocene transition.
C. J. Hollis, B. R. Hines, K. Littler, V. Villasante-Marcos, D. K. Kulhanek, C. P. Strong, J. C. Zachos, S. M. Eggins, L. Northcote, and A. Phillips
Clim. Past, 11, 1009–1025, https://doi.org/10.5194/cp-11-1009-2015, https://doi.org/10.5194/cp-11-1009-2015, 2015
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Re-examination of a Deep Sea Drilling Project sediment core (DSDP Site 277) from the western Campbell Plateau has identified the initial phase of the Paleocene-Eocene Thermal Maximum (PETM) within nannofossil chalk, the first record of the PETM in an oceanic setting in the southern Pacific Ocean (paleolatitude of ~65°S). Geochemical proxies indicate that intermediate and surface waters warmed by ~6° at the onset of the PETM prior to the full development of the negative δ13C excursion.
E. O. Walliser, B. R. Schöne, T. Tütken, J. Zirkel, K. I. Grimm, and J. Pross
Clim. Past, 11, 653–668, https://doi.org/10.5194/cp-11-653-2015, https://doi.org/10.5194/cp-11-653-2015, 2015
A. M. Snelling, G. E. A. Swann, J. Pike, and M. J. Leng
Clim. Past, 10, 1837–1842, https://doi.org/10.5194/cp-10-1837-2014, https://doi.org/10.5194/cp-10-1837-2014, 2014
K. T. Lawrence, I. Bailey, and M. E. Raymo
Clim. Past, 9, 2391–2397, https://doi.org/10.5194/cp-9-2391-2013, https://doi.org/10.5194/cp-9-2391-2013, 2013
C. F. Dawber and A. K. Tripati
Clim. Past, 8, 1957–1971, https://doi.org/10.5194/cp-8-1957-2012, https://doi.org/10.5194/cp-8-1957-2012, 2012
G. E. A. Swann and S. V. Patwardhan
Clim. Past, 7, 65–74, https://doi.org/10.5194/cp-7-65-2011, https://doi.org/10.5194/cp-7-65-2011, 2011
Cited articles
Abell, J. T., Winckler, G., Anderson, R. F., and Herbert, T. D.: Poleward and weakened westerlies during Pliocene warmth, Nature, 589, 70–75, https://doi.org/10.1038/s41586-020-03062-1, 2021.
Acker, J. G. and Leptoukh, G.: Online analysis enhances use of NASA Earth science data, Eos T. Am. Geophys. Un., 88, 14–17, https://doi.org/10.1029/2007EO020003, 2007.
Ai, X. E., Studer, A. S., Sigman, D. M., Martínez-García, A., Fripiat, F., Thöle, L. M., Michel, E., Gottschalk, J., Arnold, L., Moretti, S., Schmitt, M., Oleynik, S., Jaccard, S. L., and Haug, G. H.: Southern Ocean upwelling, Earth's obliquity, and glacial-interglacial atmospheric CO2 change, Science, 370, 1348–1352, https://doi.org/10.1126/science.abd2115, 2020.
Ai, X. E., Thöle, L. M., Auderset, A., Schmitt, M., Moretti, S., Studer, A. S., Michel, E., Wegmann, M., Mazaud, A., Bijl, P. K., Sigman, D. M., Martínez-García, A., and Jaccard, S. L.: The southward migration of the Antarctic Circumpolar Current enhanced oceanic degassing of carbon dioxide during the last two deglaciations, Commun. Earth Environ., 5, 1–12, https://doi.org/10.1038/s43247-024-01216-x, 2024.
Bachem, P. E., Risebrobakken, B., De Schepper, S., and McClymont, E. L.: Highly variable Pliocene sea surface conditions in the Norwegian Sea, Clim. Past, 13, 1153–1168, https://doi.org/10.5194/cp-13-1153-2017, 2017.
Bereiter, B., Eggleston, S., Schmitt, J., Nehrbass-Ahles, C., Stocker, T. F., Fischer, H., Kipfstuhl, S., and Chappellaz, J.: Revision of the EPICA Dome C CO2 record from 800 to 600 kyr before present, Geophys. Res. Lett., 42, 542–549, https://doi.org/10.1002/2014GL061957, 2015.
Bijl, P. K. and Brinkhuis, H.: Palsys.org: an open-access taxonomic and stratigraphic database of organic-walled dinoflagellate cysts, J. Micropalaeontol., 42, 309–314, https://doi.org/10.5194/jm-42-309-2023, 2023.
Bourgeois, T., Goris, N., Schwinger, J., and Tjiputra, J. F.: Stratification constrains future heat and carbon uptake in the Southern Ocean between 30° S and 55° S, Nat. Commun., 13, 340, https://doi.org/10.1038/s41467-022-27979-5, 2022.
Braaten, A. H., Jakob, K. A., Ho, S. L., Friedrich, O., Galaasen, E. V., De Schepper, S., Wilson, P. A., and Meckler, A. N.: Limited exchange between the deep Pacific and Atlantic oceans during the warm mid-Pliocene and Marine Isotope Stage M2 “glaciation”, Clim. Past, 19, 2109–2125, https://doi.org/10.5194/cp-19-2109-2023, 2023.
Brinkhuis, H., Munsterman, D. K., Sengers, M. J., Sluijs, A., Warnaar, J., and Williams, G. L.: Late eocene – Quaternary dinoflagellate cysts from odp site1168, Off Western Tasmania, Ocean Drilling Program, https://doi.org/10.2973/odp.proc.sr.189.2004, 2004.
Burton, L. E., Haywood, A. M., Tindall, J. C., Dolan, A. M., Hill, D. J., Abe-Ouchi, A., Chan, W.-L., Chandan, D., Feng, R., Hunter, S. J., Li, X., Peltier, W. R., Tan, N., Stepanek, C., and Zhang, Z.: On the climatic influence of CO2 forcing in the Pliocene, Clim. Past, 19, 747–764, https://doi.org/10.5194/cp-19-747-2023, 2023.
CenCO2PIP Consortium: Toward a Cenozoic history of atmospheric CO2, Science, 382, eadi5177, https://doi.org/10.1126/science.adi5177, 2023.
Chalk, T. B., Hain, M. P., Foster, G. L., Rohling, E. J., Sexton, P. F., Badger, M. P. S., Cherry, S. G., Hasenfratz, A. P., Haug, G. H., Jaccard, S. L., Martínez-García, A., Pälike, H., Pancost, R. D., and Wilson, P. A.: Causes of ice age intensification across the Mid-Pleistocene Transition, P. Natl. Acad. Sci. USA, 114, 13114–13119, https://doi.org/10.1073/pnas.1702143114, 2017.
Cook, C. P., van de Flierdt, T., Williams, T., Hemming, S. R., Iwai, M., Kobayashi, M., Jimenez-Espejo, F. J., Escutia, C., González, J. J., Khim, B.-K., McKay, R. M., Passchier, S., Bohaty, S. M., Riesselman, C. R., Tauxe, L., Sugisaki, S., Galindo, A. L., Patterson, M. O., Sangiorgi, F., Pierce, E. L., Brinkhuis, H., Klaus, A., Fehr, A., Bendle, J. A. P., Bijl, P. K., Carr, S. A., Dunbar, R. B., Flores, J. A., Hayden, T. G., Katsuki, K., Kong, G. S., Nakai, M., Olney, M. P., Pekar, S. F., Pross, J., Röhl, U., Sakai, T., Shrivastava, P. K., Stickley, C. E., Tuo, S., Welsh, K., and Yamane, M.: Dynamic behaviour of the East Antarctic ice sheet during Pliocene warmth, Nat. Geosci., 6, 765–769, https://doi.org/10.1038/ngeo1889, 2013.
De Boer, B., Lourens, L. J., and van de Wal, R. S. W.: Persistent 400 000 year variability of Antarctic ice volume and the carbon cycle is revealed throughout the Plio-Pleistocene, Nat. Commun., 5, 2999, https://doi.org/10.1038/ncomms3999, 2014.
De la Vega, E., Chalk, T. B., Wilson, P. A., Bysani, R. P., and Foster, G. L.: Atmospheric CO2 during the Mid-Piacenzian Warm Period and the M2 glaciation, Sci. Rep., 10, 11002, https://doi.org/10.1038/s41598-020-67154-8, 2020.
De la Vega, E., Chalk, T. B., Hain, M. P., Wilding, M. R., Casey, D., Gledhill, R., Luo, C., Wilson, P. A., and Foster, G. L.: Orbital CO2 reconstruction using boron isotopes during the late Pleistocene, an assessment of accuracy, Clim. Past, 19, 2493–2510, https://doi.org/10.5194/cp-19-2493-2023, 2023.
De Schepper, S., Head, M. J., and Groeneveld, J.: North Atlantic Current variability through marine isotope stage M2 (circa 3.3 Ma) during the mid-Pliocene, Paleoceanography, 24, https://doi.org/10.1029/2008PA001725, 2009.
De Schepper, S., Fischer, E. I., Groeneveld, J., Head, M. J., and Matthiessen, J.: Deciphering the palaeoecology of Late Pliocene and Early Pleistocene dinoflagellate cysts, Palaeogeogr. Palaeocl., 309, 17–32, https://doi.org/10.1016/j.palaeo.2011.04.020, 2011.
De Schepper, S., Groeneveld, J., Naafs, B. D. A., Van Renterghem, C., Hennissen, J., Head, M. J., Louwye, S., and Fabian, K.: Northern Hemisphere Glaciation during the Globally Warm Early Late Pliocene, PLoS ONE, 8, e81508, https://doi.org/10.1371/journal.pone.0081508, 2013.
De Schepper, S., Gibbard, P. L., Salzmann, U., and Ehlers, J.: A global synthesis of the marine and terrestrial evidence for glaciation during the Pliocene Epoch, Earth-Sci. Rev., 135, 83–102, https://doi.org/10.1016/j.earscirev.2014.04.003, 2014.
Egleston, E. S., Sabine, C. L., and Morel, F. M. M.: Revelle revisited: Buffer factors that quantify the response of ocean chemistry to changes in DIC and alkalinity, Global Biogeochem. Cy., 24, GB1002, https://doi.org/10.1029/2008GB003407, 2010.
Exon, N. F., Kennett, J. P., and Malone, M. J.: Ocean Drilling Program Leg 189 Initial Reports, Chap. 3, http://www-odp.tamu.edu/publications/189_IR/chap_03/chap_03.htm (last access: 6 January 2025), 2001.
Flesche Kleiven, H., Jansen, E., Fronval, T., and Smith, T. M.: Intensification of Northern Hemisphere glaciations in the circum Atlantic region (3.5–2.4 Ma) – ice-rafted detritus evidence, Palaeogeogr. Palaeocl., 184, 213–223, https://doi.org/10.1016/S0031-0182(01)00407-2, 2002.
Foster, G. L.: Seawater pH, pCO2 and [CO2-3] variations in the Caribbean Sea over the last 130 kyr: A boron isotope and B/Ca study of planktic foraminifera, Earth Planet. Sc. Lett., 271, 254–266, https://doi.org/10.1016/j.epsl.2008.04.015, 2008.
Gottschalk, J., Battaglia, G., Fischer, H., Frölicher, T. L., Jaccard, S. L., Jeltsch-Thömmes, A., Joos, F., Köhler, P., Meissner, K. J., Menviel, L., Nehrbass-Ahles, C., Schmitt, J., Schmittner, A., Skinner, L. C., and Stocker, T. F.: Mechanisms of millennial-scale atmospheric CO2 change in numerical model simulations, Quaternary Sci. Rev., 220, 30–74, https://doi.org/10.1016/j.quascirev.2019.05.013, 2019.
Groeneveld, J., Henderiks, J., Renema, W., McHugh, C. M., De Vleeschouwer, D., Christensen, B. A., Fulthorpe, C. S., Reuning, L., Gallagher, S. J., Bogus, K., Auer, G., Ishiwa, T., and Expedition 356 Scientists: Australian shelf sediments reveal shifts in Miocene Southern Hemisphere westerlies, Sci. Adv., 3, e1602567, https://doi.org/10.1126/sciadv.1602567, 2017.
Gruber, N., Gloor, M., Mikaloff Fletcher, S. E., Doney, S. C., Dutkiewicz, S., Follows, M. J., Gerber, M., Jacobson, A. R., Joos, F., Lindsay, K., Menemenlis, D., Mouchet, A., Müller, S. A., Sarmiento, J. L., and Takahashi, T.: Oceanic sources, sinks, and transport of atmospheric CO2, Global Biogeochem. Cy., 23, GB1005, https://doi.org/10.1029/2008GB003349, 2009.
Gruber, N., Bakker, D. C. E., DeVries, T., Gregor, L., Hauck, J., Landschützer, P., McKinley, G. A., and Müller, J. D.: Trends and variability in the ocean carbon sink, Nat. Rev. Earth Environ., 4, 119–134, https://doi.org/10.1038/s43017-022-00381-x, 2023.
Han, Z., Zhang, Q., Li, Q., Feng, R., Haywood, A. M., Tindall, J. C., Hunter, S. J., Otto-Bliesner, B. L., Brady, E. C., Rosenbloom, N., Zhang, Z., Li, X., Guo, C., Nisancioglu, K. H., Stepanek, C., Lohmann, G., Sohl, L. E., Chandler, M. A., Tan, N., Ramstein, G., Baatsen, M. L. J., von der Heydt, A. S., Chandan, D., Peltier, W. R., Williams, C. J. R., Lunt, D. J., Cheng, J., Wen, Q., and Burls, N. J.: Evaluating the large-scale hydrological cycle response within the Pliocene Model Intercomparison Project Phase 2 (PlioMIP2) ensemble, Clim. Past, 17, 2537–2558, https://doi.org/10.5194/cp-17-2537-2021, 2021.
Haywood, A. M., Tindall, J. C., Dowsett, H. J., Dolan, A. M., Foley, K. M., Hunter, S. J., Hill, D. J., Chan, W.-L., Abe-Ouchi, A., Stepanek, C., Lohmann, G., Chandan, D., Peltier, W. R., Tan, N., Contoux, C., Ramstein, G., Li, X., Zhang, Z., Guo, C., Nisancioglu, K. H., Zhang, Q., Li, Q., Kamae, Y., Chandler, M. A., Sohl, L. E., Otto-Bliesner, B. L., Feng, R., Brady, E. C., von der Heydt, A. S., Baatsen, M. L. J., and Lunt, D. J.: The Pliocene Model Intercomparison Project Phase 2: large-scale climate features and climate sensitivity, Clim. Past, 16, 2095–2123, https://doi.org/10.5194/cp-16-2095-2020, 2020.
Heath, R. A.: A review of the physical oceanography of the seas around New Zealand – 1982, New Zeal. J. Mar. Fresh., 19, 79–124, https://doi.org/10.1080/00288330.1985.9516077, 1985.
Hennissen, J. A. I., Head, M. J., De Schepper, S., and Groeneveld, J.: Dinoflagellate cyst paleoecology during the Pliocene–Pleistocene climatic transition in the North Atlantic, Palaeogeogr. Palaeocl., 470, 81–108, https://doi.org/10.1016/j.palaeo.2016.12.023, 2017.
Ho, S. L. and Laepple, T.: Flat meridional temperature gradient in the early Eocene in the subsurface rather than surface ocean, Nat. Geosci., 9, 606–610, https://doi.org/10.1038/ngeo2763, 2016.
Hoem, F. S., Sauermilch, I., Hou, S., Brinkhuis, H., Sangiorgi, F., and Bijl, P. K.: Late Eocene–early Miocene evolution of the southern Australian subtropical front: a marine palynological approach, J. Micropalaeontol., 40, 175–193, https://doi.org/10.5194/jm-40-175-2021, 2021.
Hoem, F. S., Sauermilch, I., Aleksinski, A. K., Huber, M., Peterse, F., Sangiorgi, F., and Bijl, P. K.: Strength and variability of the Oligocene Southern Ocean surface temperature gradient, Commun. Earth Environ., 3, 322, https://doi.org/10.1038/s43247-022-00666-5, 2022.
Hou, S.: Data from manuscripts “Reconciling equatorward migration of Southern Ocean fronts with minor Antarctic ice volume change during Miocene cooling” and “Southern Ocean control on atmospheric CO2 changes across late-Pliocene Marine Isotope Stage M2” by Suning Hou and others, Zenodo [data set], https://doi.org/10.5281/zenodo.13850979, 2024.
Hou, S., Lamprou, F., Hoem, F. S., Hadju, M. R. N., Sangiorgi, F., Peterse, F., and Bijl, P. K.: Lipid-biomarker-based sea surface temperature record offshore Tasmania over the last 23 million years, Clim. Past, 19, 787–802, https://doi.org/10.5194/cp-19-787-2023, 2023a.
Hou, S., Stap, L. B., Paul, R., Nelissen, M., Hoem, F. S., Ziegler, M., Sluijs, A., Sangiorgi, F., and Bijl, P. K.: Reconciling Southern Ocean fronts equatorward migration with minor Antarctic ice volume change during Miocene cooling, Nat. Commun., 14, 7230, https://doi.org/10.1038/s41467-023-43106-4, 2023b.
IPCC: Special Report on the Ocean and Cryosphere in a Changing Climate, https://www.ipcc.ch/srocc/ (last access: 6 January 2025), 2019.
Keigwin, L.: Pliocene stable-isotope record of deep sea drilling project site 606: Sequential events of 18O enrichment beginning AT 3.1 MA, U. S. Government Printing Office, https://doi.org/10.2973/dsdp.proc.94.1987, 1987.
Kim, J.-H., van der Meer, J., Schouten, S., Helmke, P., Willmott, V., Sangiorgi, F., Koç, N., Hopmans, E. C., and Damsté, J. S. S.: New indices and calibrations derived from the distribution of crenarchaeal isoprenoid tetraether lipids: Implications for past sea surface temperature reconstructions, Geochim. Cosmochim. Ac., 74, 4639–4654, https://doi.org/10.1016/j.gca.2010.05.027, 2010.
Kirby, N., Bailey, I., Lang, D. C., Brombacher, A., Chalk, T. B., Parker, R. L., Crocker, A. J., Taylor, V. E., Milton, J. A., Foster, G. L., Raymo, M. E., Kroon, D., Bell, D. B., and Wilson, P. A.: On climate and abyssal circulation in the Atlantic Ocean during late Pliocene marine isotope stage M2, ∼3.3 million years ago, Quaternary Sci. Rev., 250, 106644, https://doi.org/10.1016/j.quascirev.2020.106644, 2020.
Kocken, I. J., Müller, I. A., and Ziegler, M.: Optimizing the Use of Carbonate Standards to Minimize Uncertainties in Clumped Isotope Data, Geochem. Geophy. Geosy., 20, 5565–5577, https://doi.org/10.1029/2019GC008545, 2019.
Kohfeld, K. E. and Chase, Z.: Temporal evolution of mechanisms controlling ocean carbon uptake during the last glacial cycle, Earth Planet. Sc. Lett., 472, 206–215, https://doi.org/10.1016/j.epsl.2017.05.015, 2017.
Laskar, J., Robutel, P., Joutel, F., Gastineau, M., Correia, A. C. M., and Levrard, B.: A long-term numerical solution for the insolation quantities of the Earth, Aatron. Astrophys., 428, 261–285, https://doi.org/10.1051/0004-6361:20041335, 2004.
Lawrence, K. T., Herbert, T. D., Brown, C. M., Raymo, M. E., and Haywood, A. M.: High-amplitude variations in North Atlantic sea surface temperature during the early Pliocene warm period, Paleoceanography, 24, PA2218, https://doi.org/10.1029/2008PA001669, 2009.
Li, M., Hinnov, L., and Kump, L.: Acycle: Time-series analysis software for paleoclimate research and education, Comput. Geosci., 127, 12–22, https://doi.org/10.1016/j.cageo.2019.02.011, 2019.
Lisiecki, L. E. and Raymo, M. E.: A Pliocene–Pleistocene stack of 57 globally distributed benthic δ18O records: Pliocene–Pleistocene benthic stack, Paleoceanography, 20, PA1003, https://doi.org/10.1029/2004PA001071, 2005.
Liu, J., Tian, J., Liu, Z., Herbert, T. D., Fedorov, A. V., and Lyle, M.: Eastern equatorial Pacific cold tongue evolution since the late Miocene linked to extratropical climate, Sci. Adv., 5, eaau6060, https://doi.org/10.1126/sciadv.aau6060, 2019.
Liu, X., Huber, M., Foster, G. L., Dessler, A., and Zhang, Y. G.: Persistent high latitude amplification of the Pacific Ocean over the past 10 million years, Nat. Commun., 13, 7310, https://doi.org/10.1038/s41467-022-35011-z, 2022.
Martin, J. H.: Glacial-interglacial CO2 change: The Iron Hypothesis, Paleoceanography, 5, 1–13, https://doi.org/10.1029/PA005i001p00001, 1990.
Martínez-Botí, M. A., Foster, G. L., Chalk, T. B., Rohling, E. J., Sexton, P. F., Lunt, D. J., Pancost, R. D., Badger, M. P. S., and Schmidt, D. N.: Plio-Pleistocene climate sensitivity evaluated using high-resolution CO2 records, Nature, 518, 49–54, https://doi.org/10.1038/nature14145, 2015.
Martínez-Garcia, A., Rosell-Melé, A., McClymont, E. L., Gersonde, R., and Haug, G. H.: Subpolar Link to the Emergence of the Modern Equatorial Pacific Cold Tongue, Science, 328, 1550–1553, https://doi.org/10.1126/science.1184480, 2010.
Martínez-García, A., Sigman, D. M., Ren, H., Anderson, R. F., Straub, M., Hodell, D. A., Jaccard, S. L., Eglinton, T. I., and Haug, G. H.: Iron Fertilization of the Subantarctic Ocean During the Last Ice Age, Science, 343, 1347–1350, https://doi.org/10.1126/science.1246848, 2014.
Mas e Braga, M., Jones, R. S., Bernales, J., Andersen, J. L., Fredin, O., Morlighem, M., Koester, A. J., Lifton, N. A., Harbor, J. M., Suganuma, Y., Glasser, N. F., Rogozhina, I., and Stroeven, A. P.: A thicker Antarctic ice stream during the mid-Pliocene warm period, Commun. Earth Environ., 4, 1–13, https://doi.org/10.1038/s43247-023-00983-3, 2023.
McClymont, E. L., Ford, H. L., Ho, S. L., Tindall, J. C., Haywood, A. M., Alonso-Garcia, M., Bailey, I., Berke, M. A., Littler, K., Patterson, M. O., Petrick, B., Peterse, F., Ravelo, A. C., Risebrobakken, B., De Schepper, S., Swann, G. E. A., Thirumalai, K., Tierney, J. E., van der Weijst, C., White, S., Abe-Ouchi, A., Baatsen, M. L. J., Brady, E. C., Chan, W.-L., Chandan, D., Feng, R., Guo, C., von der Heydt, A. S., Hunter, S., Li, X., Lohmann, G., Nisancioglu, K. H., Otto-Bliesner, B. L., Peltier, W. R., Stepanek, C., and Zhang, Z.: Lessons from a high−CO2 world: an ocean view from ∼3 million years ago, Clim. Past, 16, 1599–1615, https://doi.org/10.5194/cp-16-1599-2020, 2020.
McKay, R., Naish, T., Carter, L., Riesselman, C., Dunbar, R., Sjunneskog, C., Winter, D., Sangiorgi, F., Warren, C., Pagani, M., Schouten, S., Willmott, V., Levy, R., DeConto, R., and Powell, R. D.: Antarctic and Southern Ocean influences on Late Pliocene global cooling, P. Natl. Acad. Sci. USA, 109, 6423–6428, https://doi.org/10.1073/pnas.1112248109, 2012.
Merino, N., Le Sommer, J., Durand, G., Jourdain, N. C., Madec, G., Mathiot, P., and Tournadre, J.: Antarctic icebergs melt over the Southern Ocean: Climatology and impact on sea ice, Ocean Model., 104, 99–110, https://doi.org/10.1016/j.ocemod.2016.05.001, 2016.
Müller, P. J., Kirst, G., Ruhland, G., von Storch, I., and Rosell-Melé, A.: Calibration of the alkenone paleotemperature index U37K' based on core-tops from the eastern South Atlantic and the global ocean (60° N–60° S), Geochim. Cosmochim. Ac., 62, 1757–1772, https://doi.org/10.1016/S0016-7037(98)00097-0, 1998.
Naafs, B. D. A., Hefter, J., Acton, G., Haug, G. H., Martínez-Garcia, A., Pancost, R., and Stein, R.: Strengthening of North American dust sources during the late Pliocene (2.7 Ma), Earth Planet. Sc. Lett., 317–318, 8–19, https://doi.org/10.1016/j.epsl.2011.11.026, 2012.
Patterson, M. O., McKay, R., Naish, T., Escutia, C., Jimenez-Espejo, F. J., Raymo, M. E., Meyers, S. R., Tauxe, L., and Brinkhuis, H.: Orbital forcing of the East Antarctic ice sheet during the Pliocene and Early Pleistocene, Nat. Geosci., 7, 841–847, https://doi.org/10.1038/ngeo2273, 2014.
Rae, J. W. B., Burke, A., Robinson, L. F., Adkins, J. F., Chen, T., Cole, C., Greenop, R., Li, T., Littley, E. F. M., Nita, D. C., Stewart, J. A., and Taylor, B. J.: CO2 storage and release in the deep Southern Ocean on millennial to centennial timescales, Nature, 562, 569–573, https://doi.org/10.1038/s41586-018-0614-0, 2018.
Reagan, J. R., P., B., Tim, E, G., Hernán, A, L., Ricardo, K., B., Olga, Courtney, B., L., C., Scott, V, M., Alexey, R, P., Christopher, Dan, S., Zhankun, W., and Dmitry, D.: World Ocean Atlas 2023 (NCEI Accession 0270533), NCEI, https://doi.org/10.25921/va26-hv25, 2023.
Risebrobakken, B., Andersson, C., De Schepper, S., and McClymont, E. L.: Low-frequency Pliocene climate variability in the eastern Nordic Seas, Paleoceanography, 31, 1154–1175, https://doi.org/10.1002/2015PA002918, 2016.
Sabine, C. L., Feely, R. A., Gruber, N., Key, R. M., Lee, K., Bullister, J. L., Wanninkhof, R., Wong, C. S., Wallace, D. W. R., Tilbrook, B., Millero, F. J., Peng, T.-H., Kozyr, A., Ono, T., and Rios, A. F.: The Oceanic Sink for Anthropogenic CO2, Science, 305, 367–371, https://doi.org/10.1126/science.1097403, 2004.
Sangiorgi, F., Bijl, P. K., Passchier, S., Salzmann, U., Schouten, S., McKay, R., Cody, R. D., Pross, J., van de Flierdt, T., Bohaty, S. M., Levy, R., Williams, T., Escutia, C., and Brinkhuis, H.: Southern Ocean warming and Wilkes Land ice sheet retreat during the mid-Miocene, Nat. Commun., 9, 317, https://doi.org/10.1038/s41467-017-02609-7, 2018.
Seki, O., Foster, G. L., Schmidt, D. N., Mackensen, A., Kawamura, K., and Pancost, R. D.: Alkenone and boron-based Pliocene pCO2 records, Earth Planet. Sc. Lett., 292, 201–211, https://doi.org/10.1016/j.epsl.2010.01.037, 2010.
Shackleton, N. J., Hall, M. A., and Pate: Proceedings of the Ocean Drilling Program, 138 Scientific Results, Ocean Drilling Program, https://doi.org/10.2973/odp.proc.sr.138.1995, 1995.
Sigman, D. M., Hain, M. P., and Haug, G. H.: The polar ocean and glacial cycles in atmospheric CO2 concentration, Nature, 466, 47–55, https://doi.org/10.1038/nature09149, 2010.
Skinner, L. C., Fallon, S., Waelbroeck, C., Michel, E., and Barker, S.: Ventilation of the Deep Southern Ocean and Deglacial CO2 Rise, Science, 328, 1147–1151, https://doi.org/10.1126/science.1183627, 2010.
Stickley, C. E., Fuller, M., Kelly, D. C., Nürnberg, D., Pfuhl, H. A., Schellenberg, S. A., Schoenfeld, J., Suzuki, N., Touchard, Y., Wei, W., Williams, G. L., Lara, J., and Stant, S. A.: Proceedings of the Ocean Drilling Program, 189 Scientific Results, edited by: Exon, N. F., Kennett, J. P., and Malone, M. J., Ocean Drilling Program, https://doi.org/10.2973/odp.proc.sr.189.2004, 2004.
Stockmarr, J.: Tables with spores used in absolute pollen analysis, Poll. Spor., 13, 615–621, 1971.
Taylor, K. W. R., Huber, M., Hollis, C. J., Hernandez-Sanchez, M. T., and Pancost, R. D.: Re-evaluating modern and Palaeogene GDGT distributions: Implications for SST reconstructions, Global Planet. Change, 108, 158–174, https://doi.org/10.1016/j.gloplacha.2013.06.011, 2013.
Teruel, O., Rosell-Melè, A., and Penalva-Arias, N.: Global patterns of oceanic dust deposition during Pliocene-Pleistocene transitions, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10616, https://doi.org/10.5194/egusphere-egu21-10616, 2021.
Thöle, L. M., Amsler, H. E., Moretti, S., Auderset, A., Gilgannon, J., Lippold, J., Vogel, H., Crosta, X., Mazaud, A., Michel, E., Martínez-García, A., and Jaccard, S. L.: Glacial-interglacial dust and export production records from the Southern Indian Ocean, Earth Planet. Sc. Lett., 525, 115716, https://doi.org/10.1016/j.epsl.2019.115716, 2019.
Thöle, L. M., Nooteboom, P. D., Hou, S., Wang, R., Nie, S., Michel, E., Sauermilch, I., Marret, F., Sangiorgi, F., and Bijl, P. K.: An expanded database of Southern Hemisphere surface sediment dinoflagellate cyst assemblages and their oceanographic affinities, J. Micropalaeontol., 42, 35–56, https://doi.org/10.5194/jm-42-35-2023, 2023.
Tiedemann, R., Sarnthein, M., and Shackleton, N. J.: Astronomic timescale for the Pliocene Atlantic δ18O and dust flux records of Ocean Drilling Program Site 659, Paleoceanography, 9, 619–638, https://doi.org/10.1029/94PA00208, 1994.
Tierney, J. E. and Tingley, M. P.: A Bayesian, spatially-varying calibration model for the TEX86 proxy, Geochim. Cosmochim. Ac., 127, 83–106, https://doi.org/10.1016/j.gca.2013.11.026, 2014.
Toggweiler, J. R., Russell, J. L., and Carson, S. R.: Midlatitude westerlies, atmospheric CO2, and climate change during the ice ages: Westerlies and CO2 during the Ice Ages, Paleoceanography, 21, PA2005, https://doi.org/10.1029/2005PA001154, 2006.
Van der Weijst, C. M. H., van der Laan, K. J., Peterse, F., Reichart, G.-J., Sangiorgi, F., Schouten, S., Veenstra, T. J. T., and Sluijs, A.: A 15-million-year surface- and subsurface-integrated TEX86 temperature record from the eastern equatorial Atlantic, Clim. Past, 18, 1947–1962, https://doi.org/10.5194/cp-18-1947-2022, 2022.
Venugopal, A. U., Bertler, N. A. N., Severinghaus, J. P., Brook, E. J., Cortese, G., Lee, J. E., Blunier, T., Mayewski, P. A., Kjær, H. A., Carter, L., Weber, M. E., Levy, R. H., Pyne, R. L., and Vandergoes, M. J.: Antarctic evidence for an abrupt northward shift of the Southern Hemisphere westerlies at 32 ka BP, Nat. Commun., 14, 5432, https://doi.org/10.1038/s41467-023-40951-1, 2023.
Weiffenbach, J. E., Dijkstra, H. A., von der Heydt, A. S., Abe-Ouchi, A., Chan, W.-L., Chandan, D., Feng, R., Haywood, A. M., Hunter, S. J., Li, X., Otto-Bliesner, B. L., Peltier, W. R., Stepanek, C., Tan, N., Tindall, J. C., and Zhang, Z.: Highly stratified mid-Pliocene Southern Ocean in PlioMIP2, Clim. Past, 20, 1067–1086, https://doi.org/10.5194/cp-20-1067-2024, 2024.
Westerhold, T., Marwan, N., Drury, A. J., Liebrand, D., Agnini, C., Anagnostou, E., Barnet, J. S. K., Bohaty, S. M., De Vleeschouwer, D., Florindo, F., Frederichs, T., Hodell, D. A., Holbourn, A. E., Kroon, D., Lauretano, V., Littler, K., Lourens, L. J., Lyle, M., Pälike, H., Röhl, U., Tian, J., Wilkens, R. H., Wilson, P. A., and Zachos, J. C.: An astronomically dated record of Earth's climate and its predictability over the last 66 million years, Science, 369, 1383–1387, https://doi.org/10.1126/science.aba6853, 2020.
Yamane, M., Yokoyama, Y., Abe-Ouchi, A., Obrochta, S., Saito, F., Moriwaki, K., and Matsuzaki, H.: Exposure age and ice-sheet model constraints on Pliocene East Antarctic ice sheet dynamics, Nat. Commun., 6, 7016, https://doi.org/10.1038/ncomms8016, 2015.
Yan, Y., Bender, M. L., Brook, E. J., Clifford, H. M., Kemeny, P. C., Kurbatov, A. V., Mackay, S., Mayewski, P. A., Ng, J., Severinghaus, J. P., and Higgins, J. A.: Two-million-year-old snapshots of atmospheric gases from Antarctic ice, Nature, 574, 663–666, https://doi.org/10.1038/s41586-019-1692-3, 2019.
Zhang, Z., Nisancioglu, K. H., and Ninnemann, U. S.: Increased ventilation of Antarctic deep water during the warm mid-Pliocene, Nat. Commun., 4, 1499, https://doi.org/10.1038/ncomms2521, 2013.
Zhang, Z., Li, X., Guo, C., Otterå, O. H., Nisancioglu, K. H., Tan, N., Contoux, C., Ramstein, G., Feng, R., Otto-Bliesner, B. L., Brady, E., Chandan, D., Peltier, W. R., Baatsen, M. L. J., von der Heydt, A. S., Weiffenbach, J. E., Stepanek, C., Lohmann, G., Zhang, Q., Li, Q., Chandler, M. A., Sohl, L. E., Haywood, A. M., Hunter, S. J., Tindall, J. C., Williams, C., Lunt, D. J., Chan, W.-L., and Abe-Ouchi, A.: Mid-Pliocene Atlantic Meridional Overturning Circulation simulated in PlioMIP2, Clim. Past, 17, 529–543, https://doi.org/10.5194/cp-17-529-2021, 2021.
Ziegler, M., Diz, P., Hall, I. R., and Zahn, R.: Millennial-scale changes in atmospheric CO2 levels linked to the Southern Ocean carbon isotope gradient and dust flux, Nat. Geosci., 6, 457–461, https://doi.org/10.1038/ngeo1782, 2013.
Zonneveld, K. A. F., Marret, F., Versteegh, G. J. M., Bogus, K., Bonnet, S., Bouimetarhan, I., Crouch, E., de Vernal, A., Elshanawany, R., Edwards, L., Esper, O., Forke, S., Grøsfjeld, K., Henry, M., Holzwarth, U., Kielt, J.-F., Kim, S.-Y., Ladouceur, S., Ledu, D., Chen, L., Limoges, A., Londeix, L., Lu, S.-H., Mahmoud, M. S., Marino, G., Matsouka, K., Matthiessen, J., Mildenhal, D. C., Mudie, P., Neil, H. L., Pospelova, V., Qi, Y., Radi, T., Richerol, T., Rochon, A., Sangiorgi, F., Solignac, S., Turon, J.-L., Verleye, T., Wang, Y., Wang, Z., and Young, M.: Atlas of modern dinoflagellate cyst distribution based on 2405 data points, Rev. Palaeobot. Palyno., 191, 1–197, https://doi.org/10.1016/j.revpalbo.2012.08.003, 2013.
Short summary
Based on dinoflagellate cyst assemblages and sea surface temperature records west of offshore Tasmania, we find a northward migration and freshening of the subtropical front, not at the M2 glacial maximum but at its deglaciation phase. This oceanographic change aligns well with trends in pCO2. We propose that iceberg discharge from the M2 deglaciation freshened the subtropical front, which together with the other oceanographic changes affected atmosphere–ocean CO2 exchange in the Southern Ocean.
Based on dinoflagellate cyst assemblages and sea surface temperature records west of offshore...
