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Benthic δ18O records Earth’s energy imbalance


Oxygen isotope ratios (δ18O) of foraminifera in marine sediment records have fundamentally shaped our understanding of the ice ages and global climate change. Interpretation of these records has, however, been challenging because they reflect contributions from both ocean temperature and ice volume. Here, instead of disentangling, we reconstruct global benthic foraminiferal δ18O across the last deglaciation (18–11.5 ka) with ice volume constraints from fossil corals and ocean temperature constraints from ice core noble gases. We demonstrate that, while ocean temperature and ice volume histories are distinct, their summed contributions to δ18O agree remarkably well with benthic δ18O records. Given the agreement between predicted and observed δ18O, we further build upon recent insight into global energy fluxes and introduce a framework to quantitively reconstruct top-of-atmosphere net radiative imbalance, or Earth’s energy imbalance, from δ18O. Finally, we reconstruct 150,000 years of energy imbalance, which broadly follows Northern Hemisphere summer insolation but shows millennial-scale energy gain during the cold intervals surrounding Heinrich events. This suggests that, in addition to external forcing, internal variability plays an important role in modifying the global energy budget on long (millennial-plus) timescales.

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Fig. 1: Contributions of ocean temperature and ice volume changes to global Δδ18O.
Fig. 2: Sensitivity of LGM Δδ18Opredicted to mean δ18Oice, noble gas saturation state and applied sea level reconstruction.
Fig. 3: Global energy change (ΔEglobal) and EEI on a range of timescales.

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File including the reconstructions from this study and original data used to produce reconstructions is available at


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We thank M. Bender, J. Higgins and J. Severinghaus for helpful discussions and encouragement in pursuing this project. We are grateful to J. Severinghaus for pointing us to the Great Barrier Reef sea level reconstruction. Thanks to S. Hines for her expertise and advice on the interpretation of marine sediment records. The first author was supported by National Science Foundation awards 1744993 and 2052958. A.S. was supported by National Science Foundation award 2049359.

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Authors and Affiliations



S.S. and D.B. designed the research. A.S. and S.S. established the method for splined reconstructions via Monte Carlo error propagation. D.B. and S.S. re-analysed the published noble gas records to produce the splined ocean temperature reconstruction. S.S., A.S., D.B. and L.E.L. analysed the data. S.S. wrote the paper with input from all authors.

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Correspondence to Sarah Shackleton.

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Nature Geoscience thanks the anonymous reviewers for their contribution to the peer review of this work. Primary Handling Editor: James Super, in collaboration with the Nature Geoscience team.

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Extended data

Extended Data Fig. 1 Global mean ocean temperature (MOT) evolution over the last 25 ka.

Individual samples from WAIS Divide18 (WDC, blue), EPICA Dome C16 (EDC, red) and Taylor Glacier20,40 (TG, yellow) are shown as points with 1σ error bars calculated from published analytical uncertainties and uncertainties associated with box model inputs (see Methods). Splined reconstruction from these combined data (MOTcomb) are shown in green with 1σ confidence envelope shown in shading centered on mean spline (solid line). Note that absolute mean ocean temperature (rather than temperature anomaly) is shown here.

Extended Data Fig. 2 Raw relative sea level data and calculated eustatic sea level curves considered in this study.

In a) points represent the individual raw observations from refs. 17 (yellow) and29 (orange) and solid lines show the splines of the eustatic sea level curves from each study that are used to compute the ice volume component of δ18Obenth. b) shows the number of raw sea level observations for each study per thousand-year bin.

Extended Data Fig. 3

Agnostic reconstruction of Earth’s energy imbalance (EEI) from δ18Obenth. Here we outline the steps taken to calculate EEI from δ18Obenth (left to right), which are described in detail in the methods. Briefly, δ18Obenth21 (left) is converted into sea level (second panel, top in yellow) and ocean temperature (second panel, bottom in green) using the assumption that the δ18Obenth signal is entirely attributed to one or the other. We then calculate the energy change associated with ice sheet buildup/melting from the sea level reconstruction (third panel, yellow) and with ocean warming/cooling from the ocean temperature reconstruction (third panel, green). EEI is then calculated by taking the time derivative of the energy changes and averaging over Earth’s surface area (panel 4). The gray lines in panels 3 and 4 show the calculated the global energy change (ΔEglobal) and EEI if we assume a constant 60/40 split of δ18Obenth between ice volume and ocean temperature changes.

Extended Data Fig. 4

Sensitivity of calculated (a) global energy change (ΔEglobal) and (b) Earth’s energy imbalance (EEI) to applied δ18Oice. Here we assume the δ18Obenth21 record is entirely an ice volume signal and calculate the energy change using a wide range of mean ice sheet δ18O (−35‰ to −25‰) to test the sensitivity of calculated EEI to this parameter.

Extended Data Fig. 5 Mean ocean temperature40 and sea level35,41 reconstructions for Termination II and the Last Interglacial.

Blue show sea level reconstructions from Red Sea plankonic δ18O35 and red diamonds show coral records from the Seychelles41. Dashed line indicates the onset and end of the termination and orange shading indicates the timing of Heinrich Stadial 11.

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Shackleton, S., Seltzer, A., Baggenstos, D. et al. Benthic δ18O records Earth’s energy imbalance. Nat. Geosci. 16, 797–802 (2023).

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