Dynamics of Surface to Intermediate-Mode Water in the Pleistocene Subantarctic Pacific (DYNAPACC Expedition 383)

亚南极洋的变化及其与大气的相互作用被认为是了解轨道至千年时间尺度气候变化的关键组成部分。海冰覆盖、海洋分层、生物养分利用以及中层和深层水通风等方面的冰期至间冰期变化在更新世大气CO2浓度的自然变化中起着关键作用。我们计划重建南大洋中层水（SOIW）的历史。1.5 Ma关于（1）（亚）海面到深层温跃层分层、温度和盐度变化（2）与绕极深水（CDW）相关的通风和碳酸盐化学，以及由此产生的碳循环变化，（2）通过海洋隧道与低纬度的潜在联系。我们采用了一种结合稳定同位素（δ 18 O，δ 13 C，δ 11 B）和元素地球化学（Mg/Ca，B/Ca）的多物种的方法。利用浅居和生活在温跃层和中层沃茨较深的物种，重建了上加利福尼亚州。500 m水柱应根据最近383号考察期间钻探的两个IODP现场确定，即东太平洋海隆中上层的U1541和智利大陆边缘的U1542。以前的工作表明表面和温跃层模式之间的差异发展，指出在冰川间冰期形成的SOIW的变化，或横向平流内的东南太平洋环流，可能连接到南西风带的变化。碳同位素应用于重建中层和上层海洋沃茨之间的古化学史，而有孔虫的δ 11 B测量应提供对直接相关的碳酸盐化学变化的进一步了解。为了实现分区重建和对亚千年SOIW动态的高分辨率观察，半远洋IODP站点U1542应提供关于SOIW的物理条件和地球化学特征的信息。SOIW有可能通过海洋隧道机制向太平洋中低纬度地区提供营养物质，这是提高低纬度生物初级生产力所急需的。这种南方来源的养分泄漏最近受到来自北太平洋的中间水重建的挑战，是一个持续辩论的问题。概述的有孔虫分析是补充高分辨率XRF核心扫描数据在（次）千年尺度分辨率的网站U1542，和较低的（次）轨道尺度分辨率网站U1541重建生产力和变化的流量制度的东南太平洋环流和南极绕极流。

Changes in the subantarctic Southern Ocean and their interaction with the atmosphere are regarded as key components for understanding climate change on orbital to millennial timescales. Glacial to interglacial variations in sea-ice cover, ocean stratification, biological nutrient utilization and ventilation of intermediate and deep water play a key role in natural variations of Pleistocene atmospheric CO2 concentrations. We plan to reconstruct the history of Southern Ocean Intermediate Water (SOIW) for the last ca. 1.5 Ma with regard to (1) (sub)seasurface to deep thermocline stratification, temperature and salinity variations (2) ventilation and carbonate chemistry in relation to Circumpolar Deepwater (CDW), and resulting carbon cycle changes, (2) potential connections to lower latitudes via ocean tunneling. We use a planktic foraminiferal multi-species approach, combining stable isotope (18O, 13C, 11B) and elemental geochemistry (Mg/Ca, B/Ca). Using both shallow-dwelling and species living deeper in thermocline and intermediate waters, a reconstruction of the upper ca. 500 m water column shall be established based on two IODP Sites drilled during recent Expedition 383, U1541 from the pelagic East Pacific Rise and U1542 from the Chilean continental margin. Previous works have indicated differential developments between surface and thermocline patterns, pointing to variations in glacial-interglacial formation of SOIW, or lateral advection within the SE Pacific Gyre, potentially connected to changes of the Southern Westerly Wind Belt. Carbon isotopes shall be used to reconstruct the paleo-chemical history between mid-depth and upper ocean waters, while foraminiferal ∂11B measurements shall provide additional insight into directly associated carbonate chemistry changes. To attain both a zonal reconstruction and a high-resolution view into sub-millennial SOIW dynamics, hemipelagic IODP Site U1542 shall provide information on the physical conditioning and biogeochemical characteristics of SOIW. SOIW was potentially provisioning mid- to lower Pacific latitudes via the ocean tunnel mechanism with nutrients, critically needed to enhance low-latitude biological primary productivity. This southern-sourced nutrient leakage has been recently challenged intermediate water reconstructions from the North Pacific and is a matter of ongoing debate. The outlined foraminiferal analyses are supplemented high-resolution XRF core scanning data at (sub-)millennial-scale resolution on site U1542, and lower (sub)orbital-scale resolution on Sites U1541 to reconstruct productivity and changes in the flow regime of the SE Pacific Gyre and Antarctic Circumpolar Current.