Mean global ocean temperatures during the last glacial transition


Little is known about the ocean temperature’s long-term response to climate perturbations owing to limited observations and a lack of robust reconstructions. Although most of the anthropogenic heat added to the climate system has been taken up by the ocean up until now, its role in a century and beyond is uncertain. Here, using noble gases trapped in ice cores, we show that the mean global ocean temperature increased by 2.57 ± 0.24 degrees Celsius over the last glacial transition (20,000 to 10,000 years ago). Our reconstruction provides unprecedented precision and temporal resolution for the integrated global ocean, in contrast to the depth-, region-, organism- and season-specific estimates provided by other methods. We find that the mean global ocean temperature is closely correlated with Antarctic temperature and has no lead or lag with atmospheric CO2, thereby confirming the important role of Southern Hemisphere climate in global climate trends. We also reveal an enigmatic 700-year warming during the early Younger Dryas period (about 12,000 years ago) that surpasses estimates of modern ocean heat uptake.

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Figure 1: Schematic of the four-box model used to derive MOT, including the modern (‘Today’) and LGM characteristics of the boxes.
Figure 2: MOT records relative to today derived from three different atmospheric noble gas ratios and their mixture.
Figure 3: Comparison of our best-estimate MOT record with other palaeoclimatic records for the last glacial transition.


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This work was supported by the Swiss National Science Foundation (scholarship P2BEP2_152071), by the US National Science Foundation (grants 05-38630 and 09-44343 to J.S.) and by the JSPS KAKENHI (grants 21671001, 26241011, 15KK0027 and 17H06320 to K.K.). We thank C. Buizert for providing the WAIS divide past firn temperature modelling results and P. Pfister for providing the Bern3D model results. We are deeply indebted to many participants in the WAIS Divide project and especially thank K. Taylor, M. Twickler, the National Ice Core Laboratory, the Ice Drilling Design and Operations (IDDO) for ice drilling, the New York Air National Guard for airlift, and the Office of Polar Programs of the US National Science Foundation. R. Keeling first provided the idea for the noble-gas-based determination of mean ocean temperature.

Author information




B.B. and D.B. performed the experiments and analysed the ice samples, and S.S. provided assistance. B.B. analysed the data and J.S. reviewed it. B.B. performed the simulations and data evaluations. J.S. supervised the project. K.K. developed central parts of the method used. B.B. drafted and wrote the manuscript and J.S., D.B. and S.S. reviewed it.

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Correspondence to Bernhard Bereiter.

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Reviewer Information Nature thanks W. Aeschbach, R. Stanley and the other anonymous reviewer(s) for their contribution to the peer review of this work.

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Extended data figures and tables

Extended Data Figure 1 Elements related to the gravitational and thermal correction applied to the ice core data.

a, Residual of the isotope data after correction for gravitational enrichment in the firn based on δ40Ar (orange) and modelled firn thermal gradients (b, green36). In contrast to δ15N (black), δ86Kr (purple) clearly deviates from the zero line by −56 per meg on average, showing that our correction factors for δ86Kr are over-estimated (δ40Ar is zero by definition because we use this data for the correction). Error bars represent the 1σ analytical uncertainty of our method based on repeated measurements of modern air samples10. b, The two independent WAIS Divide ice core site firn thermal gradient scenarios used in this study. The blue trace represents the scenario derived from our isotope data for δ15N, δ40Ar and δ86Kr, while first we corrected δ86Kr by the offset seen in a. The green trace represents the model-based scenario and originates from ref. 36. Source data

Extended Data Figure 2 Raw atmospheric noble gas elemental ratios and relative differences between individual MOT records.

a, Reconstructed atmospheric elemental ratios (orange, δKr/N2; red, δXe/N2; purple, δXe/Kr) using δ40Ar to correct for gravitational enrichment in the firn, and using the firn thermal gradient scenario based on our isotope data (see Extended Data Fig. 1) to correct for thermal fractionation. The error bars are 1σ. b, Differences in MOT derived from each of the three individual gas ratios relative to the best-estimate (Mix) data (compare with Fig. 1; orange, Kr/N2 versus Mix; red, Xe/N2 versus Mix; purple, Xe/Kr versus Mix). Source data

Extended Data Table 1 Effects of box-model elements on the LGM–Holocene MOT difference
Extended Data Table 2 Simulated ocean and surface temperatures

Supplementary information

Supplementary Data

The basic raw isotope and elemental ratios referenced to the current atmosphere as derived from the WAIS divide ice core samples. (XLSX 21 kb)

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Bereiter, B., Shackleton, S., Baggenstos, D. et al. Mean global ocean temperatures during the last glacial transition. Nature 553, 39–44 (2018).

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