Tracking Past Shifts of the Eastern Pacific ITCZ with Oxygen Isotopes and Magnesium Paleothermometry

摘要：在这个奖项下，PI将重建太平洋热带辐合带(ITCZ)的纬向迁移。该盆地ITCZ的位置和纬度范围与ENSO动力学和赤道上升流的强度密不可分，后者通过ENSO遥相关等多种机制影响全球气候。此外，ITCZ变化导致的异常热带降雨模式可能通过控制表层盐度影响海洋的温盐循环，改变陆地上的水分和生态系统平衡，通过陆地植被和生物地球化学过程(例如甲烷排放和碳储存)触发气候反馈。倡导者提议进行一项研究，以调查这一系统在轨道频带内的变异性，包括0-25万年BP的间隔，包括冰期2、6和8以及间冰期1、5和7。这一研究足够长，除了岁差和倾角强迫(19-23Ky和41Ky)之外，还可以辨别冰川-间冰期(G-I)(100Ky)的变异性。这项工作将集中在赤道N-S断面(7N-2S)的四个深海岩芯上，并将分别测量浮游有孔虫氧同位素(D18O)和镁/钙比作为表层海洋水文和温度的替代指标。

Abstract: Under this award the PIs will reconstruct the latitudinal migrations of the Intertropical Convergence Zone (ITCZ) in the Pacific Ocean. The location and latitudinal range of the ITCZ in this basin is inseparably tied to ENSO dynamics and to the strength of the equatorial upwelling, which affect global climate through various mechanisms such as ENSO teleconnections. Moreover, anomalous tropical rainfall patterns due to ITCZ shifts can impact the ocean's thermohaline circulation through control of surface salinity, and alter moisture and ecosystem balance over land triggering climate feedbacks via land-vegetation and biogeochemical processes (e.g. methane emissions and carbon storage). The proponents propose a study to investigate variability in this system in the orbital frequency band, encompassing the interval 0-250,000 years BP, which includes glacial stages 2, 6 and 8, and interglacial stages 1, 5 and 7. This is sufficiently long to discern glacial-interglacial (G-I) (100 ky) variability in addition to precession and obliquity forcing (19-23 ky, and 41 ky). The work will focus on four deep sea cores in a N-S transect across the equator (7N-2S) and will involve measurements of planktonic foraminiferal oxygen isotope (d18O) and Mg/Ca ratios as proxies of surface ocean hydrology and temperature respectively.