Hydrographic response of the East China Sea to the sea level changes lead by the glacial/interglacial climatic cycle inferred from radiolarian data (IODP exp. 346 Site U1429)

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Author(s): Matsuzaki, Kenji Marc Raymond; Itaki, Takuya
Author Affiliation(s): Primary:
University of Tokyo, Earth and Planetary Science, Bunkyo-ku, Japan
Geological Survey of Japan, Japan
Volume Title: AGU 2016 fall meeting
Source: American Geophysical Union Fall Meeting, Vol.2016; American Geophysical Union 2016 fall meeting, San Francisco, CA, Dec. 12-16, 2016. Publisher: American Geophysical Union, Washington, DC, United States
Note: In English
Summary: The East China Sea (ECS) is a marginal sea. In this area warm water of the Kuroshio Current (KC) and discharges of fresh water from the Yangtze River during summer influence the regional hydrography under the control of the East Asian Monsoon. Most parts of this sea lies above a continental shelf. Indeed, 70% of this sea has a water column shallower than 200 m. Since the end of the Mid Pleistocene Transition spanning from 1200 to 800 kyr, Earth's climate is characterized by 100 kyr interglacial/glacial climatic cycles. To these cycles are associated high amplitude changes in the world wide sea level caused by the increases/decreases in the volume of the polar ice sheets located in both hemispheres. At its maximum a Δ sea level exceeding 100 m is recognized during the glacial Marine Isotopic Stage (MIS) 2. In this context, because 70% of the ECS show a water depth shallower than 200 m, in this study we are interested in monitoring the response of the ECS hydrography to these high amplitude sea level changes. In summer-autumn 2013, the IODP Expedition 346 could retrieve sediments cores in the northern East China Sea from Site U1428 and U1429. Based on the shipboard preliminary results, these sites likely cover the past 400 kyr continuously. The shipboard preliminarily data also reported that siliceous microfossils such as radiolarians were abundant and well preserved in sediment cores collected from these sites. Radiolarian are widely distributed in the world ocean and they are famous for living from shallow to deep water masses. Therefore, their uses enable to monitor paleoecological changes in the shallow to the deep water layers. In this study based on radiolarian species, which ecology are well-known, we discuss changes in the ECS hydrography throughout the past 400 kyr. We have analyzed changes in radiolarian assemblages over 110 samples collected from Site U1429. As a preliminary result, we identified that during the MIS 2, 6 and 10 because of a globally low sea-level, the ECS continental shelf could have emerged. However, the MIS 8, known for be a glacial with a relatively high sea-level show particular hydrography.
Year of Publication: 2016
Research Program: IODP Integrated Ocean Drilling Program
Key Words: 24 Surficial Geology, Quaternary Geology; East China Sea; Expedition 346; Glacial environment; IODP Site U1428; IODP Site U1429; Integrated Ocean Drilling Program; Interglacial environment; Invertebrata; Microfossils; North Pacific; Northwest Pacific; Pacific Ocean; Paleo-oceanography; Paleoclimatology; Paleoenvironment; Protista; Radiolaria; West Pacific
Coordinates: N314038 N314039 E1290200 E1290200
N313702 N313703 E1285951 E1285951
Record ID: 2017051555
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