International Ocean Discovery Program; Expedition 379 preliminary report; Amundsen Sea West Antarctic ice sheet history; development and sensitivity of the West Antarctic ice sheet tested from drill records of the Amundsen Sea Embayment; 18 January-20 March 2019

Online Access: Get full text
doi: 10.14379/iodp.pr.379.2019
Author(s): Gohl, Karsten; Wellner, Julia S.; Klaus, Adam; Bauersachs, Thorsten; Bohaty, Steven M.; Courtillat, Margot; Cowan, Ellen A.; Esteves, Mariana S. R.; De Lira Mota, Marcelo A.; Fegyveresi, John M.; Frederichs, Thomas; Gao Liang; Halberstadt, Anna Ruth; Hillenbrand, Claus-Dieter; Horikawa, Keiji; Iwai, Masao; Kim, Ji-Hoon; King, Theresa M.; Klages, Johann P.; Passchier, Sandra; Penkrot, Michelle L.; Prebble, Joseph G.; Rahaman, Waliur; Reinardy, Benedict T. I.; Renaudie, Johan; Robinson, Delaney E.; Scherer, Reed P.; Siddoway, Christine S.; Wu Li; Yamane, Masako
International Ocean Discovery Program, Expedition 379 Scientists, College Station, TX
Author Affiliation(s): Primary:
Alfred Wegener Isntitute, Helmholtz Center for Polar and Marine Research, Germany
Other:
University of Houston, United States
Texas A&M University, United States
Christian-Albrechts University of Kiel, Germany
University of Southampton, United Kingdom
University of Perpignan, France
Appalachian State University, United States
Arctic University of Norway-University of Tromso, Norway
University of Birmingham, United Kingdom
U. S. Army Corps of Engineers, Engineer Research and Development Center, United States
University of Bremen, Germany
China University of Geosciences, China
University of Massachusetts at Amherst, United States
British Anatarctic Survey, United Kingdom
University of Toyama, Japan
Kochi University, Japan
Korea Institute of Geoscience and Mineral Resources, South Korea
University of South Florida, United States
Montclair State University, United States
Uniersity of Florida, United States
GNS Science, New Zealand
National Centre for Antarctic and Ocean Research, India
Stockholm University, Sweden
Leibniz-Institut für Evolutions und Biodiversitätsforschung, Germany
Northern Illinois University, United States
Colorado College, United States
Tongji University, China
Nagoya University, Japan
Source: Preliminary Report - International Ocean Discovery Program, Vol.379, 33p. Publisher: International Ocean Discovery Program, College Station, TX, United States. ISSN: 2372-9562
Note: In English. 116 refs.
Summary: The Amundsen Sea sector of Antarctica has long been considered the most vulnerable part of the West Antarctic Ice Sheet (WAIS) because of the great water depth at the grounding line and the absence of substantial ice shelves. Glaciers in this configuration are thought to be susceptible to rapid or runaway retreat. Ice flowing into the Amundsen Sea Embayment is undergoing the most rapid changes of any sector of the Antarctic Ice Sheet outside the Antarctic Peninsula, including changes caused by substantial grounding-line retreat over recent decades, as observed from satellite data. Recent models suggest that a threshold leading to the collapse of WAIS in this sector may have been already crossed and that much of the ice sheet could be lost even under relatively moderate greenhouse gas emission scenarios. Drill cores from the Amundsen Sea provide tests of several key questions about controls on ice sheet stability. The cores offer a direct record of glacial history offshore from a drainage basin that receives ice exclusively from the WAIS, which allows clear comparisons between the WAIS history and low-latitude climate records. Today, warm Circumpolar Deep Water (CDW) is impinging onto the Amundsen Sea shelf and causing melting of the underside of the WAIS in most places. Reconstructions of past CDW intrusions can assess the ties between warm water upwelling and large-scale changes in past grounding-line positions. Carrying out these reconstructions offshore from the drainage basin that currently has the most substantial negative mass balance of ice anywhere in Antarctica is thus of prime interest to future predictions. The scientific objectives for this expedition are built on hypotheses about WAIS dynamics and related paleoenvironmental and paleoclimatic conditions. The main objectives are 1. To test the hypothesis that WAIS collapses occurred during the Neogene and Quaternary and, if so, when and under which environmental conditions; 2. To obtain ice-proximal records of ice sheet dynamics in the Amundsen Sea that correlate with global records of ice-volume changes and proxy records for atmospheric and ocean temperatures; 3. To study the stability of a marine-based WAIS margin and how warm deep-water incursions control its position on the shelf; 4. To find evidence for earliest major grounded WAIS advances onto the middle and outer shelf; 5. To test the hypothesis that the first major WAIS growth was related to the uplift of the Marie Byrd Land dome. International Ocean Discovery Program (IODP) Expedition 379 completed two very successful drill sites on the continental rise of the Amundsen Sea. Site U1532 is located on a large sediment drift, now called Resolution Drift, and penetrated to 794 m with 90% recovery. We collected almost-continuous cores from the Pleistocene through the Pliocene and into the late Miocene. At Site U1533, we drilled 383 m (70% recovery) into the more condensed sequence at the lower flank of the same sediment drift. The cores of both sites contain unique records that will enable study of the cyclicity of ice sheet advance and retreat processes as well as bottom-water circulation and water mass changes. In particular, Site U1532 revealed a sequence of Pliocene sediments with an excellent paleomagnetic record for high-resolution climate change studies of the previously sparsely sampled Pacific sector of the West Antarctic margin. Despite the drilling success at these sites, the overall expedition experienced three unexpected difficulties that affected many of the scientific objectives: 1. The extensive sea ice on the continental shelf prevented us from drilling any of the proposed shelf sites. 2. The drill sites on the continental rise were in the path of numerous icebergs of various sizes that frequently forced us to pause drilling or leave the hole entirely as they approached the ship. The overall downtime caused by approaching icebergs was 50% of our time spent on site. 3. An unfortunate injury to a member of the ship's crew cut the expedition short by one week. Recovery of core on the continental rise at Sites U1532 and U1533 cannot be used to precisely indicate the position of ice or retreat of the ice sheet on the shelf. However, these sediments contained in the cores offer a range of clues about past WAIS extent and retreat. At Sites U1532 and U1533, coarse-grained sediments interpreted to be ice-rafted debris (IRD) were identified throughout all recovered time periods. A dominant feature of the cores is recorded by lithofacies cyclicity, which is interpreted to represent relatively warmer periods variably characterized by higher microfossil abundance, greater bioturbation, and higher counts of IRD alternating with colder periods characterized by dominantly gray laminated terrigenous muds.
Year of Publication: 2019
Research Program: IODP Integrated Ocean Drilling Program
IODP2 International Ocean Discovery Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; 20 Geophysics, Applied; Algae; Amundsen Sea; Antarctic ice sheet; Antarctica; Arthropoda; Biostratigraphy; Boreholes; Cenozoic; Chemostratigraphy; Cores; Crustacea; Deglaciation; Depositional environment; Diatoms; Dinoflagellata; Expedition 379; Foraminifera; Geophysical methods; Geophysical profiles; Geophysical surveys; Glacial environment; Glacial geology; Glaciation; IODP Site U1532; IODP Site U1533; Ice sheets; International Ocean Discovery Program; Lithofacies; Lithostratigraphy; Magnetostratigraphy; Mandibulata; Marine sediments; Microfossils; Miocene; Nannofossils; Neogene; Ostracoda; Paleo-oceanography; Paleoclimatology; Palynomorphs; Physical properties; Pleistocene; Quaternary; Radiolaria; Sediments; Seismic methods; Seismic profiles; Seismic stratigraphy; Surveys; Tertiary; Well logs; West Antarctic ice sheet
Coordinates: S683900 S683900 W1073200 W1073200
S684400 S684400 W1090200 W1090200
Record ID: 2019046858
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute.