IODP Expedition 346: Asian Monsoon

        Integrated Ocean Drilling Program (IODP) Expedition 346 (29 July–27 September 2013) drilled seven sites covering a wide latitudinal range in the body of water bordered by the Eurasian continent, the Korean Peninsula, and the Japanese Islands, as well as two closely spaced sites in the East China Sea. This expedition recovered 6135.3 m of core with an average recovery of 101%—a record amount of core recovered during any single IODP expedition. Expedition 346 was the first scientific drilling expedition ever to focus exclusively on the climate system in this region, which is at once so critical yet potentially vulnerable to the challenges society faces in the coming years of global climate change. With the East Asian Monsoon directly affecting the water supply of one-third of the global population, the expedition scientific results and postexpedition research that will follow have direct bearing on society’s understanding of this complex atmosphere-ocean climate system.

        The high quality of materials recovered and the complete documentation of their geological, geochemical, and geophysical context will lead to an unparalleled series of future studies by the expedition Science Party as well as many other scientists over the coming decades. Cores obtained during this expedition will be used 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 and East Asian winter monsoon and provided teleconnection mechanism(s) for Dansgaard–Oeschger cycles.

        Recent and novel advances in drilling technology and newly developed analytical tools enabled the collection and examination of sediment records that were impossible to acquire even a few years ago. The newly engineered half advanced piston corer enabled recovery of the deepest piston core in Deep Sea Drilling Project/Ocean Drilling Program/IODP history (490.4 m in IODP Hole U1427A); that achievement was also the deepest continuously recovered piston cored sequence, initiated at the mudline and penetrating to ~500 m core depth below seafloor, Method A (m CSF-A). Technological advances delivered a series of “new surprises” (e.g., pristine dark–light laminae from ~12 Ma sediment recovered by piston core from 410 m CSF-A at IODP Site U1425 and from 210 m CSF-A at IODP Site U1430) that will stimulate new scientific inquiry into climate dynamics during a time frame and with a high fidelity that could have only been imagined by scientists even a short time ago. High-resolution geochemistry studies targeting the anaerobic oxidation of methane and the relationships between metal chemistry and the degradation of organic carbon were performed to study the fate of organic carbon in the marine system and constrain rates of microbial reactions in the deep biosphere with a novel fluid extraction technique. Finely tuned comparisons were developed between disparate geographic locations and demonstrated synchroneity in this marginal sea's regional response to internal and external climate-related forcing.

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