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Active Nordic Seas deep-water formation during the last glacial maximum

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Abstract

The Nordic Seas are the primary location where the warm waters of the North Atlantic Current densify to form North Atlantic Deep Water, which plays a key part in the modern Atlantic Meridional Overturning Circulation. The formation of dense water in the Nordic Seas and Arctic Ocean and resulting ocean circulation changes were probably driven by and contributed to the regional and global climate of the last glacial maximum (LGM). Here we map the source and degree of mixing of deep water in the Nordic Seas and through the Arctic Gateway (Yermak Plateau) over the past 35 thousand years using neodymium isotopes (εNd) measured on authigenic phases in deep-sea sediments with a high spatial and temporal resolution. We find that a large-scale reorganization of deep-water formation in the Nordic Seas took place between the LGM (23–18 thousand years ago) and the rapid climate shift that accompanied the subsequent deglaciation (18–10 thousand years ago). We show that homogeneous εNd signatures across a wide range of sites support LGM deep-water formation in the Nordic Seas. In contrast, during the deglaciation, disparate and spatially variable εNd values are observed leading to the conclusion that deep-water formation may have been reduced during this time.

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Fig. 1: Deep-sea sediment core locations.
Fig. 2: Arctic Ocean, Nordic Seas and northeast Atlantic neodymium isotope reconstructions over the past 35 ka.
Fig. 3: Time-slice reconstructions of Arctic Ocean, Nordic Seas and northeast Atlantic εNd.
Fig. 4: Histogram and probability distribution of Nordic Seas and Yermak Plateau εNd.

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Data availability

All data from this study can be found in the supplementary information (data tables) and can be accessed through the PANGAEA data archive.

Code availability

All modelling and statistical analysis was carried out with the use of published open-access software in R, as referenced in Methods. R codes used for the numerical procedures are available from the corresponding author upon reasonable request.

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Acknowledgements

C.S.L. thanks T. Williams, V. Rennie, R. Wang, M.-L. Bagard, J. Hall, S. Crowhurst, G. Dipre and H. Chapman for assistance in the lab. C.S.L. is grateful to K. Hogan and C. Xuan for suggesting core locations. We thank the British Ocean Sediment Core Research Facility, the Byrd Polar and Climate Research Center, Lamont–Doherty Core Repository and International Ocean Discovery Program for supplying sediment samples used in this study. C.S.L. was funded by a NERC studentship (NE/L002507/1) with support from Murray Edwards College and the Geological Society’s Elspeth Matthews Fund. Radiocarbon analysis was supported by NERC Radiocarbon Facility NRCF010001 to A.M.P., S.G.M. and C.S.L. (allocation number 2117.0418). M.M.E. is funded by the Research Council of Norway and the Co-funding of Regional, National and International Programmes (COFUND)–Marie Sklodowska-Curie Actions under the European Union Seventh Framework Programme (FP7), project number 274429, and the Tromsø Research Foundation, project number A31720. M.M.E. and T.L.R. received funding from the Research Council of Norway through its Centres of Excellence funding scheme, grant number 223259.

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Authors and Affiliations

  1. Department of Earth Sciences, University of Cambridge, Cambridge, UK

    Christina S. Larkin, Mohamed M. Ezat, Natalie L. Roberts, Edward T. Tipper & Alex M. Piotrowski

  2. School of Ocean and Earth Science, University of Southampton, National Oceanography Centre, Southampton, UK

    Christina S. Larkin

  3. Murray Edwards College, University of Cambridge, Cambridge, UK

    Christina S. Larkin & Alex M. Piotrowski

  4. CAGE–Centre for Arctic Gas Hydrate, Environment and Climate, Department of Geosciences, UiT the Arctic University of Norway, Tromsø, Norway

    Mohamed M. Ezat & Tine L. Rasmussen

  5. Department of Geology, Faculty of Science, Beni-Suef University, Beni-Suef, Egypt

    Mohamed M. Ezat

  6. Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany

    Henning A. Bauch

  7. GEOMAR Helmholtz Centre for Ocean Research, Kiel, Germany

    Henning A. Bauch & Robert F. Spielhagen

  8. The University Centre in Svalbard, Longyearbyen, Norway

    Riko Noormets

  9. Byrd Polar and Climate Research Center, Ohio State University, Columbus, USA

    Leonid Polyak

  10. NERC Radiocarbon Facility, East Kilbride, UK

    Steven G. Moreton

  11. Christian-Albrechts University, Kiel, Germany

    Michael Sarnthein

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  1. Christina S. Larkin
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Contributions

The research was planned by C.S.L., A.M.P. and E.T.T., with input from all authors. Analysis was carried out by C.S.L., apart from as follows: data from core PS1243 was obtained by N.L.R. Materials were supplied by H.A.B., R.F.S., L.P., T.L.R., M.S., R.N. and M.M.E. The manuscript was written by C.S.L. with comments and contributions from all authors.

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Correspondence to Christina S. Larkin.

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Nature Geoscience thanks Patrick Blaser and the other, anonymous, reviewer(s) for their contribution to the peer review of this work. Editor Recognition: Primary Handling Editor(s): James Super, in collaboration with the Nature Geoscience team.

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Extended data

Extended Data Fig. 1 εNd leachate comparison with seawater and planktic foraminifera.

Left: Cross plot of authigenic εNd measured on planktic foraminifera and bulk sediment leachates at the same depth, blue line is the linear best fit line with the 95% confidence interval shown (grey band), the associated R2 is 0.96814, and the black dashed line is the 1:1 line. 2σ error bars are smaller than symbol size. Right: Cross plot of bulk leachate core top authigenic εNd and the nearest modern seawater values20,36,37,39,40. 2σ error bars are the analytical uncertainty. The red line is the linear best fit line with the 95% confidence interval shown (grey band), and the associated R2 is 0.7545 the dashed black line is the 1:1 line.

Extended Data Fig. 2 Bayesian age models produced for deep sea sediment cores with new records presented in this study.

Using the program ‘BACON’61. Dark shading indicates the more likely ages for a given depth, and the red dashed line indicates the best-fit age model.

Extended Data Fig. 3 Nordic Seas planktic δ18O.

a, All Nordic Seas and Yermak Plateau εNd data compiled, plotted for reference. εNd data includes new data presented in this study and literature data22,33 b, Published planktic δ18O on N. pachyderma s. from the Nordic Seas9,13,69,70,71,72. δ18O is not ice-volume corrected. Blank lines show the smoothed conditional means of the data, with the 95% confidence interval in grey. Time intervals considered and defined in this study are indicated by coloured bars: late Holocene 5-0 ka, Deglacial: 18-13 ka, LGM: 23-18 ka.

Extended Data Fig. 4 Nordic Sea and Yermak Plateau deep-sea sediment core site modern water mass properties.

Symbols are sediment core locations: red squares are from this study, blue diamonds are literature data22,33. Salinity and temperature cross sections are through the Nordic Seas and Yermak Plateau (red line on map). Made using ODV. Salinity and temperature data from the World Ocean Atlas (2013), retrieved through ODV43.

Extended Data Fig. 5 Quantile-Quantile Normal plots of Nordic Seas and Yermak Plateau data.

Top left to right is modern seawater and late Holocene (5-0 ka), bottom is left to right deglacial (18-13 ka) and LGM (23-18 ka). 95% confidence interval is given (grey band) alongside the 1:1 line (black line).

Extended Data Table 1 Results of the Shapiro-Wilk test for normality carried out on Nordic Seas and Yermak Plateau εNd datasets
Full size table
Extended Data Table 2 Results of the F-test (two-tailed) used to compare variances for Nordic Seas and Yermak Plateau εNd datasets, with normal distributions
Full size table

Supplementary information

Supplementary Information

Supplementary Tables 1–7.

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Larkin, C.S., Ezat, M.M., Roberts, N.L. et al. Active Nordic Seas deep-water formation during the last glacial maximum. Nat. Geosci. 15, 925–931 (2022). https://doi.org/10.1038/s41561-022-01050-w

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