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			<titleStmt><title level='a'>Ross Sea West Antarctic Ice Sheet History</title></titleStmt>
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				<publisher></publisher>
				<date>08/10/2019</date>
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					<idno type="par_id">10224876</idno>
					<idno type="doi">10.14379/iodp.proc.374.2019</idno>
					<title level='j'>Proceedings of the International Ocean Discovery Program</title>
<idno>2377-3189</idno>
<biblScope unit="volume">374</biblScope>
<biblScope unit="issue"></biblScope>					

					<author>R.M. McKay</author><author>L. De Santis</author><author>D.K. Kulhanek</author>
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			<abstract><ab><![CDATA[The marine-based West Antarctic Ice Sheet (WAIS) is currently locally retreating because of shifting wind-driven oceanic currents that transport warm waters toward the ice margin, resulting in ice shelf thinning and accelerated mass loss. Previous results from geologic drilling on Antarctica’s continental margins show significant variability in ice sheet extent during the late Neogene and Quaternary. Climate and ice sheet models indicate a fundamental role for oceanic heat in controlling ice sheet variability over at least the past 20 My. Although evidence for past ice sheet variability is available from ice-proximal marine settings, sedimentary sequences from the continental shelf and rise are required to evaluate the extent of past ice sheet variability and the associated forcings and feedbacks. International Ocean Discovery Program Expedition 374 drilled a latitudinal and depth transect of five sites from the outer continental shelf to rise in the central Ross Sea to resolve Neogene and Quaternary relationships between climatic and oceanic change and WAIS evolution. The Ross Sea was targeted because numerical ice sheet models indicate that this sector of Antarctica responds sensitively to changes in ocean heat flux. Expedition 374 was designed for optimal data-model integration to enable an improved understanding of Antarctic Ice Sheet (AIS) mass balance during warmer-than-present climates (e.g., the Pleistocene “super interglacials,” the mid-Pliocene, and the Miocene Climatic Optimum). The principal goals of Expedition 374 were to: 1. Evaluate the contribution of West Antarctica to far-field ice volume and sea level estimates; 2. Reconstruct ice-proximal oceanic and atmospheric temperatures to quantify past polar amplification; 3. Assess the role of oceanic forcing (e.g., temperature and sea level) on AIS variability; 4. Identify the sensitivity of the AIS to Earth’s orbital configuration under a variety of climate boundary conditions; and 5. Reconstruct Ross Sea paleobathymetry to examine relationships between seafloor geometry, ice sheet variability, and global climate. To achieve these objectives, postcruise studies will: 1. Use data and models to reconcile intervals of maximum Neogene and Quaternary ice advance and retreat with far-field records of eustatic sea level; 2. Reconstruct past changes in oceanic and atmospheric temperatures using a multiproxy approach; 3. Reconstruct Neogene and Quaternary sea ice margin fluctuations and correlate these records to existing inner continental shelf records;  4. Examine relationships among WAIS variability, Earth’s orbital configuration, oceanic temperature and circulation, and atmospheric pCO2; and 5. Constrain the timing of Ross Sea continental shelf overdeepening and assess its impact on Neogene and Quaternary ice dynamics. Expedition 374 departed from Lyttelton, New Zealand, in January 2018 and returned in March 2018. We recovered 1292.70 m of high-quality core from five sites spanning the early Miocene to late Quaternary. Three sites were cored on the continental shelf (Sites U1521, U1522, and U1523). At Site U1521, we cored a 650 m thick sequence of interbedded diamictite and diatom-rich mudstone penetrating seismic Ross Sea Unconformity 4 (RSU4). The depositional reconstructions of past glacial and open-marine conditions at this site will provide unprecedented insight into environmental change on the Antarctic continental shelf during the late early and middle Miocene. At Site U1522, we cored a discontinuous late Miocene to Pleistocene sequence of glacial and glaciomarine strata from the outer shelf with the primary objective of penetrating and dating RSU3, which is interpreted to reflect the first continental shelf–wide expansion of East and West Antarctic ice streams. Site U1523, located on the outer continental shelf, targeted a sediment drift beneath the westward-flowing Antarctic Slope Current (ASC) to test the hypothesis that changes in ASC vigor regulate ocean heat flux onto the continental shelf and thus ice sheet mass balance. We also cored two sites on the continental rise and slope. At Site U1524, we recovered a Plio–Pleistocene sedimentary sequence from the levee of the Hillary Canyon, one of the largest conduits of Antarctic Bottom Water from the continental shelf to the abyssal ocean. Site U1524 was designed to penetrate into middle Miocene and older strata, but coring was initially interrupted by drifting sea ice that forced us to abandon coring in Hole U1524A at 399.5 m drilling depth below seafloor (DSF). We moved to a nearby alternate site on the continental slope (Site U1525) to core a single hole designed to complement the record at Site U1524. We returned to Site U1524 after the sea ice cleared and cored Hole U1524C with the rotary core barrel system with the intention of reaching the target depth of 1000 m DSF. However, we were forced to terminate Hole U1524C at 441.9 m DSF because of a mechanical failure with the vessel that resulted in termination of all drilling operations and forced us to return to Lyttelton 16 days earlier than scheduled. The loss of 39% of our operational days significantly impacted our ability to achieve all Expedition 374 objectives. In particular, we were not able to recover continuous middle Miocene sequences from the continental rise designed to complement the discontinuous record from continental shelf Site U1521. The mechanical failure also meant we could not recover cores from proposed Site RSCR-19A, which was targeted to obtain a high-fidelity, continuous record of upper Neogene and Quaternary pelagic/hemipelagic sedimentation. Despite our failure to recover a continental shelf-to-rise Miocene transect, records from Sites U1522, U1524, and U1525 and legacy cores from the Antarctic Geological Drilling Project (ANDRILL) can be integrated to develop a shelf-to-rise Plio–Pleistocene transect.]]></ab></abstract>
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<div xmlns="http://www.tei-c.org/ns/1.0"><head>Contents</head></div>
<div xmlns="http://www.tei-c.org/ns/1.0"><head>Expedition reports</head></div>
<div xmlns="http://www.tei-c.org/ns/1.0"><head>Chapters</head></div>
<div xmlns="http://www.tei-c.org/ns/1.0"><head>Core descriptions</head><p>Visual core descriptions (VCDs) are presented in PDF files for each site. Smear slides and/or thin sections are presented in PDF and/or CSV files for each site and/or hole (CSV files are available in the CORES directory). The entire set of core images in PDF is available in the IMAGES directory. </p></div>
<div xmlns="http://www.tei-c.org/ns/1.0"><head>Site</head></div>
<div xmlns="http://www.tei-c.org/ns/1.0"><head>Supplementary material</head><p>Supplementary material for the Volume 374 expedition reports includes DESClogik workbooks in Microsoft Excel format and hand drawn barrel sheets in PDF. A full list of directories can be found in SUPP_MAT in the volume zip folder or on the Supplementary material for Volume 374 expedition reports web page.</p></div>
<div xmlns="http://www.tei-c.org/ns/1.0"><head>Expedition research results</head></div>
<div xmlns="http://www.tei-c.org/ns/1.0"><head>Data reports</head><p>Titles are available in HTML.</p></div>
<div xmlns="http://www.tei-c.org/ns/1.0"><head>Syntheses</head><p>Titles are available in HTML. </p></div>
<div xmlns="http://www.tei-c.org/ns/1.0"><head>Drilling location maps</head></div>
<div xmlns="http://www.tei-c.org/ns/1.0"><head>Foreword</head><p>The International Ocean Discovery Program (IODP) represents the latest incarnation of almost five decades of scientific ocean drilling excellence and is generally accepted as the most successful international collaboration in the history of the Earth sciences. IODP builds seamlessly on the accomplishments of previous phases: the Deep Sea Drilling Project, Ocean Drilling Program, and Integrated Ocean Drilling Program. The 2013-2023 IODP Science Plan (Illuminating Earth's Past, Present, and Future) defines four themes and thirteen challenges for this decade of scientific ocean drilling that are both of fundamental importance in understanding how the Earth works and of significant relevance to society as the Earth changes, at least in part in response to anthropogenic forcing. This phase of IODP represents a renewed level of international collaboration in bringing diverse drilling platforms and strategies to increasing our understanding of climate and ocean change, the deep biosphere and evolution of ecosystems, connections between Earth's deep processes and surface manifestations, and geologically induced hazards on human timeframes.</p><p>The Proceedings of the International Ocean Discovery Program presents the scientific and engineering results of IODP drilling projects, expedition by expedition. As in the preceding Integrated Ocean Drilling Program, expeditions in the new IODP are conducted by three implementing organizations, each providing a different drilling capability. These are the US Implementing Organization (USIO; through September 2014) and the JOIDES Resolution Science Operator (JRSO; as of October 2014), providing the leased commercial vessel JOIDES Resolution for riserless drilling operations; JAMSTEC's Center for Deep Earth Exploration (CDEX), providing the drillship Chikyu for riser and occasional riserless operations; and the European Consortium for Ocean Research Drilling (ECORD) Science Operator (ESO), providing "mission-specific" platforms (MSPs) for expeditions that extend the IODP operational range where neither drillship is suitable, for example, in polar environments and in shallow waters. Scheduling decisions for each capability are made by three independent Facility Boards, each of which includes scientists, operators, and platform funding partners: the JOIDES Resolution Facility Board (JRFB), Chikyu IODP Board (CIB), and ECORD Facility Board (EFB). At the beginning of the new IODP, the three Facility Boards agreed to utilize Publication Services at the USIO and now the JRSO for production of all expedition Proceedings volumes and reports.</p><p>The new IODP differs from prior scientific ocean drilling programs in that it has neither a central management organization nor commingled funding for program-wide activities. Yet this phase of IODP retains a fundamental integrative structural element: a "bottom-up" evaluation of all proposals for drilling expeditions by a single advisory structure composed of scientists representing all international program partners. International scientists may submit drilling proposals to the Science Support Office; all submitted proposals are then evaluated by a Science Evaluation Panel in the context of the Science Plan.</p><p>The new IODP also has a second internationally integrative level for high-level discussion and consensus-building: the IODP Forum. The Forum is charged with assessing program-wide progress toward achieving the Science Plan. At present, IODP involves 26 international financial partners, including the United States, Japan, an Australia/New Zealand consortium (ANZIC), Brazil, China, India, South Korea, and the eighteen members of ECORD (Austria, Belgium, Canada, Denmark, Finland, France, Germany, Ireland, Israel, Italy, the Netherlands, Norway, Poland, Portugal, Spain, Sweden, Switzerland, and the United Kingdom). This enhanced membership in the new IODP represents a remarkable level of international collaboration that remains one of the greatest ongoing strengths of scientific ocean drilling. James A. Austin Jr. Chair, IODP Forum V o l u m e 3 7 4 </p></div>
<div xmlns="http://www.tei-c.org/ns/1.0"><head>International Ocean Discovery Program</head></div></body>
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