title: Antarctic ice sheet sensitivity to atmospheric CO2 variations in the early to mid-Miocene.
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.
authors.affiliation: Department of Paleontology, GNS Science, Lower Hutt, New Zealand, 5040; R.Levy@gns.cri.nz.
authors.forename: Richard
authors.initials: R
authors.lastname: Levy
authors.affiliation: Department of Earth & Atmospheric Sciences, University of Nebraska, Lincoln, NE 68588;
authors.forename: David
authors.initials: D
authors.lastname: Harwood
authors.affiliation: Istituto Nazionale di Geofisica e Vulcanologia, I-00143 Rome, Italy;
authors.forename: Fabio
authors.initials: F
authors.lastname: Florindo
authors.affiliation: Marine Palynology and Paleoceanography, Laboratory of Palaeobotany and Palynology, Department of Earth Sciences, Utrecht University, 3584 CD, Utrecht, The Netherlands;
authors.forename: Francesca
authors.initials: F
authors.lastname: Sangiorgi
authors.affiliation: 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;
authors.forename: Robert
authors.initials: R
authors.lastname: Tripati
authors.affiliation: Department of Sedimentology & Environmental Geology, Geoscience Center Göttingen, 37077 Göttingen, Germany;
authors.forename: Hilmar
authors.initials: H
authors.lastname: von Eynatten
authors.affiliation: Department of Geosciences, University of Massachusetts, Amherst, MA 01003;
authors.forename: Edward
authors.identifier: http://orcid.org/0000-0003-4653-6217
authors.initials: E
authors.lastname: Gasson
authors.affiliation: Alfred Wegener Institute for Polar & Marine Research, 27568 Bremerhaven, Germany;
authors.forename: Gerhard
authors.identifier: http://orcid.org/0000-0001-6069-7485
authors.initials: G
authors.lastname: Kuhn
authors.affiliation: 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;
authors.forename: Aradhna
authors.initials: A
authors.lastname: Tripati
authors.affiliation: Department of Geosciences, University of Massachusetts, Amherst, MA 01003;
authors.forename: Robert
authors.initials: R
authors.lastname: DeConto
authors.affiliation: Department of Earth & Atmospheric Sciences, University of Nebraska, Lincoln, NE 68588;
authors.forename: Christopher
authors.initials: C
authors.lastname: Fielding
authors.affiliation: Department of Paleontology, GNS Science, Lower Hutt, New Zealand, 5040;
authors.forename: Brad
authors.initials: B
authors.lastname: Field
authors.affiliation: Department of Paleontology, GNS Science, Lower Hutt, New Zealand, 5040; Antarctic Research Centre, Victoria University of Wellington, Wellington, New Zealand, 6012;
authors.forename: Nicholas
authors.initials: N
authors.lastname: Golledge
authors.affiliation: Antarctic Research Centre, Victoria University of Wellington, Wellington, New Zealand, 6012;
authors.forename: Robert
authors.initials: R
authors.lastname: McKay
authors.affiliation: Department of Paleontology, GNS Science, Lower Hutt, New Zealand, 5040; Antarctic Research Centre, Victoria University of Wellington, Wellington, New Zealand, 6012;
authors.forename: Timothy
authors.initials: T
authors.lastname: Naish
authors.affiliation: Hillsborough Community College, Tampa, FL 10414;
authors.forename: Matthew
authors.initials: M
authors.lastname: Olney
authors.affiliation: Earth & Environmental Systems Institute, Pennsylvania State University, University Park, PA 16802;
authors.forename: David
authors.initials: D
authors.lastname: Pollard
authors.affiliation: Marine Organic Biogeochemistry, Royal Netherlands Institute for Sea Research, 1797 SZ 't Horntje (Texel), The Netherlands;
authors.forename: Stefan
authors.initials: S
authors.lastname: Schouten
authors.affiliation: Dipartimento di Scienze Fisiche della Terra e dell'Ambiente, Università degli Studi di Siena, I-53100 Siena, Italy;
authors.forename: Franco
authors.initials: F
authors.lastname: Talarico
authors.affiliation: Department of Geology & Geophysics and Museum of Natural Science, Louisiana State University, Baton Rouge, LA 70803;
authors.forename: Sophie
authors.initials: S
authors.lastname: Warny
authors.affiliation: Alfred Wegener Institute for Polar & Marine Research, 27568 Bremerhaven, Germany;
authors.forename: Veronica
authors.initials: V
authors.lastname: Willmott
authors.affiliation: Department of Geography & Geology, Sam Houston State University, Huntsville, TX 77341;
authors.forename: Gary
authors.initials: G
authors.lastname: Acton
authors.affiliation: Department of Geology, Bowling Green State University, Bowling Green, OH 43403;
authors.forename: Kurt
authors.initials: K
authors.lastname: Panter
authors.affiliation: Department of Geology, University of Wisconsin-Oshkosh, Oshkosh, WI 54901;
authors.forename: Timothy
authors.initials: T
authors.lastname: Paulsen
authors.affiliation: Institute of Marine Sciences, National Research Council, 40129 Bologna, Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Taviani
keywords: Antarctica; Climate Optimum; Miocene; Ross Sea; ice sheet