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Levy R, Harwood D, Florindo F, Sangiorgi F, Tripati R, von Eynatten H, Gasson E, Kuhn G, Tripati A, DeConto R, Fielding C, Field B, Golledge N, McKay R, Naish T, Olney M, Pollard D, Schouten S, Talarico F, Warny S, Willmott V, Acton G, Panter K, Paulsen T, Taviani M. Antarctic ice sheet sensitivity to atmospheric CO2 variations in the early to mid-Miocene. Proc Natl Acad Sci U S A 2016; 113:3453-8. [PMID: 26903644 PMCID: PMC4822588 DOI: 10.1073/pnas.1516030113] [Citation(s) in RCA: 110] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Geological records from the Antarctic margin offer direct evidence of environmental variability at high southern latitudes and provide insight regarding ice sheet sensitivity to past climate change. The early to mid-Miocene (23-14 Mya) is a compelling interval to study as global temperatures and atmospheric CO2 concentrations were similar to those projected for coming centuries. Importantly, this time interval includes the Miocene Climatic Optimum, a period of global warmth during which average surface temperatures were 3-4 °C higher than today. Miocene sediments in the ANDRILL-2A drill core from the Western Ross Sea, Antarctica, indicate that the Antarctic ice sheet (AIS) was highly variable through this key time interval. A multiproxy dataset derived from the core identifies four distinct environmental motifs based on changes in sedimentary facies, fossil assemblages, geochemistry, and paleotemperature. Four major disconformities in the drill core coincide with regional seismic discontinuities and reflect transient expansion of grounded ice across the Ross Sea. They correlate with major positive shifts in benthic oxygen isotope records and generally coincide with intervals when atmospheric CO2 concentrations were at or below preindustrial levels (∼280 ppm). Five intervals reflect ice sheet minima and air temperatures warm enough for substantial ice mass loss during episodes of high (∼500 ppm) atmospheric CO2 These new drill core data and associated ice sheet modeling experiments indicate that polar climate and the AIS were highly sensitive to relatively small changes in atmospheric CO2 during the early to mid-Miocene.
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Affiliation(s)
- Richard Levy
- Department of Paleontology, GNS Science, Lower Hutt, New Zealand, 5040;
| | - David Harwood
- Department of Earth & Atmospheric Sciences, University of Nebraska, Lincoln, NE 68588
| | - Fabio Florindo
- Istituto Nazionale di Geofisica e Vulcanologia, I-00143 Rome, Italy
| | - Francesca Sangiorgi
- Marine Palynology and Paleoceanography, Laboratory of Palaeobotany and Palynology, Department of Earth Sciences, Utrecht University, 3584 CD, Utrecht, The Netherlands
| | - Robert Tripati
- Institute of the Environment and Sustainability, University of California, Los Angeles, CA 90024; Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles, CA 90095
| | - Hilmar von Eynatten
- Department of Sedimentology & Environmental Geology, Geoscience Center Göttingen, 37077 Göttingen, Germany
| | - Edward Gasson
- Department of Geosciences, University of Massachusetts, Amherst, MA 01003
| | - Gerhard Kuhn
- Alfred Wegener Institute for Polar & Marine Research, 27568 Bremerhaven, Germany
| | - Aradhna Tripati
- Institute of the Environment and Sustainability, University of California, Los Angeles, CA 90024; Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles, CA 90095
| | - Robert DeConto
- Department of Geosciences, University of Massachusetts, Amherst, MA 01003
| | - Christopher Fielding
- Department of Earth & Atmospheric Sciences, University of Nebraska, Lincoln, NE 68588
| | - Brad Field
- Department of Paleontology, GNS Science, Lower Hutt, New Zealand, 5040
| | - Nicholas Golledge
- Department of Paleontology, GNS Science, Lower Hutt, New Zealand, 5040; Antarctic Research Centre, Victoria University of Wellington, Wellington, New Zealand, 6012
| | - Robert McKay
- Antarctic Research Centre, Victoria University of Wellington, Wellington, New Zealand, 6012
| | - Timothy Naish
- Department of Paleontology, GNS Science, Lower Hutt, New Zealand, 5040; Antarctic Research Centre, Victoria University of Wellington, Wellington, New Zealand, 6012
| | | | - David Pollard
- Earth & Environmental Systems Institute, Pennsylvania State University, University Park, PA 16802
| | - Stefan Schouten
- Marine Organic Biogeochemistry, Royal Netherlands Institute for Sea Research, 1797 SZ 't Horntje (Texel), The Netherlands
| | - Franco Talarico
- Dipartimento di Scienze Fisiche della Terra e dell'Ambiente, Università degli Studi di Siena, I-53100 Siena, Italy
| | - Sophie Warny
- Department of Geology & Geophysics and Museum of Natural Science, Louisiana State University, Baton Rouge, LA 70803
| | - Veronica Willmott
- Alfred Wegener Institute for Polar & Marine Research, 27568 Bremerhaven, Germany
| | - Gary Acton
- Department of Geography & Geology, Sam Houston State University, Huntsville, TX 77341
| | - Kurt Panter
- Department of Geology, Bowling Green State University, Bowling Green, OH 43403
| | - Timothy Paulsen
- Department of Geology, University of Wisconsin-Oshkosh, Oshkosh, WI 54901
| | - Marco Taviani
- Institute of Marine Sciences, National Research Council, 40129 Bologna, Italy
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Galeotti S, DeConto R, Naish T, Stocchi P, Florindo F, Pagani M, Barrett P, Bohaty SM, Lanci L, Pollard D, Sandroni S, Talarico FM, Zachos JC. Antarctic Ice Sheet variability across the Eocene-Oligocene boundary climate transition. Science 2016; 352:76-80. [PMID: 27034370 DOI: 10.1126/science.aab0669] [Citation(s) in RCA: 90] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2015] [Accepted: 02/24/2016] [Indexed: 11/02/2022]
Abstract
About 34 million years ago, Earth's climate cooled and an ice sheet formed on Antarctica as atmospheric carbon dioxide (CO2) fell below ~750 parts per million (ppm). Sedimentary cycles from a drill core in the western Ross Sea provide direct evidence of orbitally controlled glacial cycles between 34 million and 31 million years ago. Initially, under atmospheric CO2 levels of ≥600 ppm, a smaller Antarctic Ice Sheet (AIS), restricted to the terrestrial continent, was highly responsive to local insolation forcing. A more stable, continental-scale ice sheet calving at the coastline did not form until ~32.8 million years ago, coincident with the earliest time that atmospheric CO2 levels fell below ~600 ppm. Our results provide insight into the potential of the AIS for threshold behavior and have implications for its sensitivity to atmospheric CO2 concentrations above present-day levels.
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Affiliation(s)
- Simone Galeotti
- Dipartimento di Scienze Pure e Applicate, Università degli Studi di Urbino "Carlo Bo," 61029 Urbino, Italy.
| | - Robert DeConto
- Department of Geosciences, University of Massachusetts, Amherst, MA, USA
| | - Timothy Naish
- Antarctic Research Centre, Victoria University of Wellington, Wellington, New Zealand. GNS Science, P.O. Box 30368, Lower Hutt, New Zealand
| | - Paolo Stocchi
- NIOZ Royal Netherlands Institute for Sea Research, Department of Coastal Systems, and Utrecht University, 1790 AB Den Burg, Texel, Netherlands
| | - Fabio Florindo
- Istituto Nazionale di Geofisica e Vulcanologia, 00143 Rome, Italy
| | - Mark Pagani
- Department of Geology and Geophysics, Yale University, New Haven, CT, USA
| | - Peter Barrett
- Antarctic Research Centre, Victoria University of Wellington, Wellington, New Zealand
| | - Steven M Bohaty
- Ocean and Earth Science, University of Southampton, National Oceanography Centre, Southampton SO14 3ZH, UK
| | - Luca Lanci
- Dipartimento di Scienze Pure e Applicate, Università degli Studi di Urbino "Carlo Bo," 61029 Urbino, Italy
| | - David Pollard
- Earth System Science Center, Pennsylvania State University, State College, PA, USA
| | - Sonia Sandroni
- Museo Nazionale dell'Antartide, Università degli Studi di Siena, 53100 Siena, Italy
| | - Franco M Talarico
- Museo Nazionale dell'Antartide, Università degli Studi di Siena, 53100 Siena, Italy. Dipartimento di Scienze Fisiche, della Terra e dell'Ambiente, Università degli Studi di Siena, 53100 Siena, Italy
| | - James C Zachos
- Earth Sciences Department, University of California, Santa Cruz, CA 95064, USA
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