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      Glacial heterogeneity in Southern Ocean carbon storage abated by fast South Indian deglacial carbon release

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          Abstract

          Past changes in ocean 14C disequilibria have been suggested to reflect the Southern Ocean control on global exogenic carbon cycling. Yet, the volumetric extent of the glacial carbon pool and the deglacial mechanisms contributing to release remineralized carbon, particularly from regions with enhanced mixing today, remain insufficiently constrained. Here, we reconstruct the deglacial ventilation history of the South Indian upwelling hotspot near Kerguelen Island, using high-resolution 14C-dating of smaller-than-conventional foraminiferal samples and multi-proxy deep-ocean oxygen estimates. We find marked regional differences in Southern Ocean overturning with distinct South Indian fingerprints on (early de-)glacial atmospheric CO 2 change. The dissipation of this heterogeneity commenced 14.6 kyr ago, signaling the onset of modern-like, strong South Indian Ocean upwelling, likely promoted by rejuvenated Atlantic overturning. Our findings highlight the South Indian Ocean’s capacity to influence atmospheric CO 2 levels and amplify the impacts of inter-hemispheric climate variability on global carbon cycling within centuries and millennia.

          Abstract

          A Southern Ocean influences on the carbon cycle is considered a key component of deglacial changes. Here, the authors show spatial differences in glacial Southern Ocean carbon storage that dissipated rapidly 14.6 kyr ago, revealing a South Indian Ocean contribution to rapid deglacial atmospheric CO 2 increases.

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          Structural absorption by barbule microstructures of super black bird of paradise feathers

          Many studies have shown how pigments and internal nanostructures generate color in nature. External surface structures can also influence appearance, such as by causing multiple scattering of light (structural absorption) to produce a velvety, super black appearance. Here we show that feathers from five species of birds of paradise (Aves: Paradisaeidae) structurally absorb incident light to produce extremely low-reflectance, super black plumages. Directional reflectance of these feathers (0.05–0.31%) approaches that of man-made ultra-absorbent materials. SEM, nano-CT, and ray-tracing simulations show that super black feathers have titled arrays of highly modified barbules, which cause more multiple scattering, resulting in more structural absorption, than normal black feathers. Super black feathers have an extreme directional reflectance bias and appear darkest when viewed from the distal direction. We hypothesize that structurally absorbing, super black plumage evolved through sensory bias to enhance the perceived brilliance of adjacent color patches during courtship display.
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            Collapse and rapid resumption of Atlantic meridional circulation linked to deglacial climate changes.

            The Atlantic meridional overturning circulation is widely believed to affect climate. Changes in ocean circulation have been inferred from records of the deep water chemical composition derived from sedimentary nutrient proxies, but their impact on climate is difficult to assess because such reconstructions provide insufficient constraints on the rate of overturning. Here we report measurements of 231Pa/230Th, a kinematic proxy for the meridional overturning circulation, in a sediment core from the subtropical North Atlantic Ocean. We find that the meridional overturning was nearly, or completely, eliminated during the coldest deglacial interval in the North Atlantic region, beginning with the catastrophic iceberg discharge Heinrich event H1, 17,500 yr ago, and declined sharply but briefly into the Younger Dryas cold event, about 12,700 yr ago. Following these cold events, the 231Pa/230Th record indicates that rapid accelerations of the meridional overturning circulation were concurrent with the two strongest regional warming events during deglaciation. These results confirm the significance of variations in the rate of the Atlantic meridional overturning circulation for abrupt climate changes.
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              Circulation, mixing, and production of Antarctic Bottom Water

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                Author and article information

                Contributors
                jgottsch@ldeo.columbia.edu
                Journal
                Nat Commun
                Nat Commun
                Nature Communications
                Nature Publishing Group UK (London )
                2041-1723
                3 December 2020
                3 December 2020
                2020
                : 11
                : 6192
                Affiliations
                [1 ]GRID grid.5734.5, ISNI 0000 0001 0726 5157, Institute of Geological Sciences and Oeschger Center for Climate Change Research, , University of Bern, ; Bern, Switzerland
                [2 ]GRID grid.21729.3f, ISNI 0000000419368729, Lamont-Doherty Earth Observatory, , Columbia University of the City of New York, ; Palisades, NY USA
                [3 ]GRID grid.460789.4, ISNI 0000 0004 4910 6535, Laboratoire des Sciences du Climat et de l’Environnement, LSCE/IPSL, CNRS-CEA-UVSQ, , Université de Paris-Saclay, ; Gif-sur-Yvette, France
                [4 ]GRID grid.5477.1, ISNI 0000000120346234, Department of Earth Sciences, Marine Palynology and Paleoceanography, , Utrecht University, ; Utrecht, Netherlands
                [5 ]GRID grid.419509.0, ISNI 0000 0004 0491 8257, Max Planck Institute for Chemistry, , Climate Geochemistry Department, ; Mainz, Germany
                [6 ]GRID grid.6612.3, ISNI 0000 0004 1937 0642, Department of Environmental Sciences, , University of Basel, ; Basel, Switzerland
                [7 ]GRID grid.5801.c, ISNI 0000 0001 2156 2780, Geological Institute, Department of Earth Sciences, , ETH Zurich, ; Zurich, Switzerland
                [8 ]GRID grid.10894.34, ISNI 0000 0001 1033 7684, Alfred-Wegener-Institut Helmholtz-Zentrum für Polar-und Meeresforschung, ; Bremerhaven, Germany
                [9 ]GRID grid.5734.5, ISNI 0000 0001 0726 5157, Department of Chemistry and Biochemistry and Oeschger Centre for Climate Change Research, , University of Bern, ; Bern, Switzerland
                [10 ]GRID grid.9851.5, ISNI 0000 0001 2165 4204, Present Address: Institute of Earth Sciences, , University of Lausanne, ; Lausanne, Switzerland
                Author information
                http://orcid.org/0000-0002-0403-3059
                http://orcid.org/0000-0001-7810-8888
                http://orcid.org/0000-0001-7354-8497
                http://orcid.org/0000-0002-9275-7304
                http://orcid.org/0000-0002-7206-5079
                http://orcid.org/0000-0002-5793-0896
                Article
                20034
                10.1038/s41467-020-20034-1
                7712879
                33273459
                7db2c93f-cfca-462d-8a41-6d37085d270e
                © The Author(s) 2020

                Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/.

                History
                : 13 May 2020
                : 5 November 2020
                Funding
                Funded by: FundRef https://doi.org/10.13039/501100001659, Deutsche Forschungsgemeinschaft (German Research Foundation);
                Award ID: GO 2294/2-1
                Award Recipient :
                Funded by: FundRef https://doi.org/10.13039/501100004359, Vetenskapsrådet (Swedish Research Council);
                Award ID: VR-349-2012-6278
                Award ID: VR-349-2012-6278
                Award Recipient :
                Funded by: FundRef https://doi.org/10.13039/501100001711, Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung (Swiss National Science Foundation);
                Award ID: PBEZP2_145695
                Award Recipient :
                Categories
                Article
                Custom metadata
                © The Author(s) 2020

                Uncategorized
                biogeochemistry,carbon cycle,climate change,palaeoceanography,palaeoclimate
                Uncategorized
                biogeochemistry, carbon cycle, climate change, palaeoceanography, palaeoclimate

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