Pleistocene evolution of eastern Pacific Southern Ocean surface water conditions

过去十年的古海洋学和气候研究证明，南大洋发生的生物和物理过程以及南极冰盖的体积和范围的变化对定义和塑造地球上的S气候起到了至关重要的作用。破译晚更新世东太平洋南大洋过程的第一步已经完成，分析了短沉积岩芯(长达25米)，只追溯到几千年前。然而，我们对南大洋长期气候发展的图景是不完整的，因为从早、中更新世获得的信息很少。在未来几年，对南大洋海洋记录的需求将越来越大，其时间跨度将与新的“旧冰”冰芯的时间跨度相匹配，该冰芯的时间跨度打算追溯到150万年前，涵盖中更新世过渡(1250至70万年前)。为了增进我们对东太平洋南大洋更新世古海洋学发展的了解，在IODP 383(U1539、U1540和U1541站点)考察期间钻探的三个沉积物记录的恢复是一个优势，可以追溯到更早的时间，以揭示亚南极地区开阔的海洋环境中的海面过程。亚南极IODP材料将由一个来自南极地带的低分辨率极地活塞芯(PS58/273-1)补充，以低分辨率覆盖整个更新世。为了建立海表面温度(SST)变化、海冰范围和生产力变化的时间序列，将从沉积物中提取硅藻组合。硅藻计数将用最近开发的传递函数定量地转换为夏季SST估计值和海冰浓度。主要目的是建立3个亚南极中东部太平洋站点和1个南极站点的高分辨率地物记录，以揭示更新世环境变化。地表夏季温度重建将与反映不同季节和水深的其他温度代理相关。重点将是高峰期间冰期(例如，海洋同位素第5和第11阶段)，特别是海洋同位素第31阶段的超间冰期。此外，岩心下部硅藻的变化可能通过融化水脉冲提供关于西南极冰盖稳定性的信息。硅藻分析的进一步机会将是硅藻生物地层学的完善，因为对南太平洋的硅藻生物地层学知之甚少。硅藻生物地层学事件将与从同一沉积物材料中提取的其他微化石的磁性地层学事件和生物地层学事件相关联，以建立目标区域改进的地层框架。

Paleoceanographic and -climatic research during the last decade has documented that bio-logical and physical processes occurring in the Southern Ocean and changes in volume and extent of the Antarctic ice sheets play a crucial role in defining and shaping Earth´s climate. A first step to decipher Late Pleistocene eastern Pacific Southern Ocean processes has been done analysing short sediment cores (up to 25-meter-long), reaching back only a few hun-dred thousand years in time. However, our picture of long-term Southern Ocean climate de-velopment is incomplete because only little information is available from the Early and Middle Pleistocene. In the coming years, there will be increasing demand on marine records from the Southern Ocean matching the time span of the new “Oldes Ice” ice core intended to reaching back to 1.5 million years, covering the Mid-Pleistocene Transition (1,250 to 700 thousand years ago). To improve our knowledge on Pleistocene paleoceanographic development in the eastern Pacific Southern Ocean the recovery of three sediment records drilled during IODP Expedition 383 (sites U1539, U1540 and U1541) is an advantage to go further back in time to unravel sea surface processes from the open ocean environments of the Subantarctic Zone. The Subantarctic IODP material will be complimented by one low-resolution POLARSTERN piston core from the Antarctic Zone (PS58/273-1), covering the entire Pleistocene epoch in low resolution. To establish time series of sea surface temperature (SST) variation, sea ice extent and productivity changes, diatom associations will be extracted from the sediments. Diatom counts will be converted quantitatively to summer SST estimates and sea ice concen-tration with recently developed transfer functions. Main aim is to establish high resolution dia-tom records from three Subantarctic central eastern Pacific sites and one Antarctic site to reveal Pleistocene environmental changes. Surface summer temperature reconstructions will be correlated to other temperature proxies reflecting different seasons and water depths. In focus will be the peak interglacials (e.g. Marine Isotope Stages 5 and 11) and especially the super interglacial of Marine Isotope Stage 31. In addition, downcore diatom variation might give information on West Antarctic Ice Sheet Stability via melt water pulses. A further oppor-tunity of diatom analysis will be the refinement of the diatom biostratigraphy, were little is known yet from the Pacific Southern Ocean. Diatom biostratigraphic events will be correlated with magnetostratigraphic events and biostratigraphic events of other microfossils retrieved from the same sediment material to establish an improved stratigraphic framework for the target region.