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doi:10.2204/iodp.sp.346.2013

Abstract

Integrated Ocean Drilling Program Expedition 346 will core and log seven sites covering a wide latitudinal range in the Japan Sea and one site in the northern East China Sea to test the hypothesis that Pliocene–Pleistocene uplift of the Himalaya and Tibetan Plateau, and the consequent emergence of the two discrete modes of Westerly Jet circulation, caused the amplification of millennial-scale variability of the East Asian summer monsoon (EASM) and East Asian winter monsoon (EAWM) and provided teleconnection mechanism(s) for Dansgaard–Oeschger cycles.

Specific scientific objectives are

• To address the timing of onset of orbital- and millennial-scale variability of the EASM and EAWM and their relation with variability of Westerly Jet circulation;
• To reconstruct orbital- and millennial-scale changes in surface and deepwater circulations and surface productivity in the Japan Sea during at least the last 5 m.y.;
• To reconstruct the history of the Yangtze River discharge using cores from the northern end of the East China Sea, as it reflects variation and evolution in EASM and exerts an impact on the paleoceanography of the Japan Sea; and
• To examine the interrelationship among the EASM, EAWM, nature and intensity of the influx through the Tsushima Strait, the intensity of winter cooling, surface productivity, ventilation, and bottom water oxygenation in the Japan Sea and their changes during the last 5 m.y.

A latitudinal transect of the Japan Sea will be cored to monitor the behaviors of the Westerly Jet, EAWM, and the Tsushima Warm Current. The southern part of the transect also will be used to reconstruct the behavior of the Subpolar Front and examine its relationship with the Westerly Jet and sea level changes, whereas the northern part of the transect will be used to identify ice-rafted debris events and reconstruct temporal variation in its southern limit. In addition, a depth transect of sites will reconstruct the ventilation history of the Japan Sea and examine the relation between ventilation and the nature of the influx through the Tsushima Strait and/or the intensity of winter cooling. We also will drill in the northern part of the East China Sea to monitor the Yangtze River discharge history that should reflect variations in EASM intensity.

Expedition 346 will potentially recover ~6060 m of sediment. Drilling strategies will include triple advanced piston corer, single or double extended core barrel, and single rotary core barrel (East China Sea) drilling. We will drill in 316–3435 m water depth. Considering the significant transit time at the beginning of the expedition (~2 weeks), this coring schedule within the remaining 6 weeks of the expedition is indeed ambitious and will require tight operational planning and flexibility. The final operations plan and number of sites to be cored is contingent upon the R/V JOIDES Resolution operations schedule, operational risks, and the outcome of requests for territorial permission to occupy particular sites.

All relevant IODP sampling and data policies will be in effect. On board sampling will be restricted to acquiring ephemeral data and to limited low-resolution sampling of parameters that may be affected by even short-term core storage. Most sampling will be deferred to a postcruise sampling party at the Kochi Core Center (KCC; Japan). An onshore “X-ray fluorescence (XRF) scanning plan” will be developed in consultation with scientific participants.

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