Plio–Pleistocene paleoceanography of the northern and western Pacific

大约280万到245万年前的新第三纪-第四纪（上新世-更新世）过渡代表了地球气候系统的一个根本转变。作为近代气候特征的极端冰期-间冰期振荡出现在这个时期，尽管其原因尚不确定。由于深海沉积物具有连续性和年代确定的特征，它们为气候历史提供了线索，而且海洋本身是至关重要的热量和二氧化碳来源/汇，同时也是冰盖生长所需水分的提供者。对北大西洋沉积物的广泛研究表明，大约在274万到260万年前，巨大的冰盖覆盖了北纬高纬度地区。

The Neogene-Quaternary (Pliocene-Pleistocene) transition around 2.8 to 2.45 million years ago represents a fundamental shift in Earth’s climate system. The extreme glacial-interglacial oscillations that characterize our more recent climate emerged at this time, although the causes remain uncertain. Deep-ocean sediments offer clues to climate history owing to their continuous and well-dated character, and because the oceans themselves are crucial heat and CO2 sources / sinks as well as being suppliers of moisture for ice sheet growth. Extensive research on North Atlantic sediments has revealed that large ice sheets covered the high northern latitudes around 2.74 and 2.6 million years ago. While research has focused mostly on the North Atlantic, plausible evidence holds that the northern Pacific Ocean supplied moisture to northern North America allowing the growth of ice sheets 2.74 million years ago. The proposed research targets five deep-sea cores along a transect from the Bering Sea to the South China Sea, and aims to elucidate the Pacific Ocean’s role in climate evolution during the Neogene-Quaternary transition. It specifically addresses ice sheet expansion 2.74 and 2.6 million years ago, and explores the associated surface current patterns. It also examines teleconnections between high northern latitude ice sheets and the East Asian winter monsoon system, as reflected in sediments of the marginal Sea of Japan and South China Sea. The intensification of this monsoon is seen in Chinese loess sequences and is driven by cooling in northern Asia. The examination of well-dated ocean sediments may therefore resolve uncertainties in the timing of Chinese loess deposition. The tools used primarily in the proposed research are the fossilized cysts of dinoflagellates: single-celled microplankton known to be sensitive to environmental change, and as a group tolerant of a wide range in salinities. The cysts (“dinocysts”) are acid-insoluble and resistant to dissolution, and are used as tracers of water masses and indicators of sea-ice extent. Acritarchs, also to be studied, occur in the same preparations as dinocysts but are of unknown biological affinity. They are abundant and relatively diverse in high northern latitudes, and have strong potential for paleoenvironmental analysis over the selected time interval. Dinocysts and acritarchs have been studied extensively in Pliocene and lower Pleistocene deposits of the North Atlantic, but have been largely neglected for the Pacific. Results will be of particular importance to the paleoclimate and paleoceanography communities, and to climate modelers who test models of future climate against evidence-based paleoclimate reconstructions. The detailed study of dinocysts and acritarchs in tandem with other paleoenvironmental proxies will enhance the utility of this microfossil group for future applications in the Pacific and elsewhere.