Plio–Pleistocene paleoceanography of the northern and western Pacific

北太平洋和西太平洋的普利奥更新世古海洋学

• 批准号: RGPIN-2016-06371
• 负责人: Head, Martin
• 金额: $ 2.4万
• 依托单位: Brock University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2016
• 资助国家: 加拿大
• 起止时间: 2016-01-01 至 2017-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=616264
• 关键词: Plio; Pleistocene; paleoceanography; northern; western

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.

大约2.8至245万年前的新近纪-第四纪（上新世-更新世）转变代表了地球气候系统的根本转变。代表我们最近气候特征的极端冰期-间冰期振荡此时出现，尽管其原因仍不确定。深海沉积物为气候历史提供了线索，因为它们具有连续性和过时性，而且海洋本身是重要的热量和二氧化碳源/汇，也是冰盖生长的水分供应者。对北大西洋沉积物的广泛研究表明，大约 2.74 至 260 万年前，大型冰盖覆盖了北部高纬度地区。 虽然研究主要集中在北大西洋，但合理的证据表明，北太平洋在 274 万年前向北美北部提供了水分，从而使冰盖得以生长。拟议的研究针对从白令海到南海的横断面的五个深海核心，旨在阐明太平洋在新近纪-第四纪过渡期间气候演变中的作用。它专门讨论了 2.74 和 260 万年前的冰盖扩张，并探索了相关的表面电流模式。它还研究了北高纬度冰盖与东亚冬季季风系统之间的遥相关，如日本边缘海和南中国海的沉积物所反映的那样。这种季风的加剧可以在中国的黄土层序中看到，并且是由亚洲北部的变冷所驱动的。因此，对年代清楚的海洋沉积物的研究可能会解决中国黄土沉积时间的不确定性。 这项研究主要使用的工具是甲藻的化石包囊：已知对环境变化敏感的单细胞微型浮游生物，并且作为一个群体能够耐受各种盐度。包囊（“双囊”）不溶于酸且耐溶解，可用作水团的示踪剂和海冰范围的指示器。 Acritarchs 也有待研究，它们与二囊虫存在于相同的制剂中，但具有未知的生物亲和力。它们在北部高纬度地区丰富且相对多样化，并且在选定的时间间隔内具有强大的古环境分析潜力。在北大西洋的上新世和下更新世沉积物中，恐龙囊和原始生物已被广泛研究，但在太平洋地区却基本上被忽视了。 结果对于古气候和古海洋学界以及根据基于证据的古气候重建测试未来气候模型的气候建模者来说特别重要。对恐龙囊和原质的详细研究与其他古环境指标相结合，将增强该微化石群在太平洋和其他地方未来应用的效用。