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      Millennial-scale variability of the Antarctic ice sheet during the early Miocene

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          Significance

          Millennial-scale cycles (1–15 kyr periods) are extensively documented in Quaternary climate proxies and linked to complex interhemispheric earth system feedbacks associated with dynamic behavior of large continental-scale ice sheets at both poles. Here, we identify millennial-scale variability in the East Antarctic ice sheet in the early Miocene, a time characterized by warmer climates, higher atmospheric pCO 2, and no large Northern Hemisphere ice sheets. These millennial-scale cycles are modulated by astronomical climate forcing, despite there being no a priori reason to expect such patterns to arise from a linear response to Milankovitch Cycles. These patterns likely arise from nonlinear interactions between the atmosphere, ocean, and ice that appear to have characterized Earth’s cryosphere for at least the past 20 My.

          Abstract

          Millennial-scale ice sheet variability (1–15 kyr periods) is well documented in the Quaternary, providing insight into critical atmosphere–ocean–cryosphere interactions that can inform the mechanism and pace of future climate change. Ice sheet variability at similar frequencies is comparatively less known and understood prior to the Quaternary during times, where higher atmospheric pCO 2 and warmer climates prevailed, and continental-scale ice sheets were largely restricted to Antarctica. In this study, we evaluate a high-resolution clast abundance dataset (ice-rafted debris) that captures East Antarctic ice sheet variability in the western Ross Sea during the early Miocene. This dataset is derived from a 100 m-thick mudstone interval in the ANtarctic DRILLing (ANDRILL or AND) core 2A, which preserves a record of precession and eccentricity variability. The sedimentation rates are of appropriate resolution to also characterize the signature of robust, subprecession cyclicity. Strong sub-precession (~10 kyr) cyclicity is observed, with an amplitude modulation in lockstep with eccentricity, indicating a relationship between high-frequency Antarctic ice sheet dynamics and astronomical forcing. Bicoherence analysis indicates that many of the observed millennial-scale cycles (as short as 1.2 kyr) are associated with nonlinear interactions (combination or difference tones) between each other and the Milankovitch cycles. The presence of these cycles during the Miocene reveals the ubiquity of millennial-scale ice sheet variability and sheds light on the interactions between Earth’s atmosphere, ocean, and ice in climates warmer than the Quaternary.

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          Most cited references106

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          Controlling the False Discovery Rate: A Practical and Powerful Approach to Multiple Testing

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            Trends, rhythms, and aberrations in global climate 65 Ma to present.

            Since 65 million years ago (Ma), Earth's climate has undergone a significant and complex evolution, the finer details of which are now coming to light through investigations of deep-sea sediment cores. This evolution includes gradual trends of warming and cooling driven by tectonic processes on time scales of 10(5) to 10(7) years, rhythmic or periodic cycles driven by orbital processes with 10(4)- to 10(6)-year cyclicity, and rare rapid aberrant shifts and extreme climate transients with durations of 10(3) to 10(5) years. Here, recent progress in defining the evolution of global climate over the Cenozoic Era is reviewed. We focus primarily on the periodic and anomalous components of variability over the early portion of this era, as constrained by the latest generation of deep-sea isotope records. We also consider how this improved perspective has led to the recognition of previously unforeseen mechanisms for altering climate.
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              Spectrum estimation and harmonic analysis

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                Author and article information

                Contributors
                Journal
                Proc Natl Acad Sci U S A
                Proc Natl Acad Sci U S A
                PNAS
                Proceedings of the National Academy of Sciences of the United States of America
                National Academy of Sciences
                0027-8424
                1091-6490
                18 September 2023
                26 September 2023
                18 March 2024
                : 120
                : 39
                : e2304152120
                Affiliations
                [1] aDepartment of Geoscience, University of Wisconsin-Madison , Madison, WI 53706
                [2] bAntarctic Research Centre, Victoria University of Wellington , Wellington 6012, New Zealand
                [3] cGeological and Nuclear Science , Lower Hutt 5040, New Zealand
                Author notes
                1To whom correspondence may be addressed. Email: nbsullivan@ 123456wisc.edu .

                Edited by Mathieu Martinez, Universite de Rennes 1, Rennes cedex, France; received March 13, 2023; accepted August 2, 2023 by Editorial Board Member Jean Jouzel

                Author information
                https://orcid.org/0000-0003-2009-8992
                https://orcid.org/0000-0003-4422-720X
                https://orcid.org/0000-0002-8783-0167
                https://orcid.org/0000-0002-5602-6985
                https://orcid.org/0000-0001-7676-8970
                https://orcid.org/0000-0003-1780-3371
                Article
                202304152
                10.1073/pnas.2304152120
                10523552
                37722047
                b220a9c1-8585-4bd8-9356-8c8c8e97f7b5
                Copyright © 2023 the Author(s). Published by PNAS.

                This article is distributed under Creative Commons Attribution-NonCommercial-NoDerivatives License 4.0 (CC BY-NC-ND).

                History
                : 13 March 2023
                : 02 August 2023
                Page count
                Pages: 8, Words: 4829
                Funding
                Funded by: Columbia | LDEO | U.S. Science Support Program, Lamont-Doherty Earth Observatory (USSSP, LDEO), FundRef 100012530;
                Award ID: Schlanger
                Award Recipient : Nicholas B. Sullivan
                Funded by: National Science Foundation (NSF), FundRef 100000001;
                Award ID: 1151438
                Award Recipient : Stephen R. Meyers
                Funded by: Heising-Simons Foundation (HSF), FundRef 100014155;
                Award ID: 2021-2797
                Award Recipient : Stephen R. Meyers
                Funded by: New Zealand Antarctic Research Institute (NZARI), FundRef 100014355;
                Award ID: ANTA1801
                Award Recipient : Richard Levy Award Recipient : Robert McKay Award Recipient : Nicholas R Golledge Award Recipient : Giuseppe Cortese
                Categories
                research-article, Research Article
                earth-sci, Earth, Atmospheric, and Planetary Sciences
                413
                Physical Sciences
                Earth, Atmospheric, and Planetary Sciences

                paleoclimate,cryosphere,miocene,cyclostratigraphy
                paleoclimate, cryosphere, miocene, cyclostratigraphy

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