Multi-proxy record of planktonic and benthic foraminiferal d18O, and Mg/Ca-derived surface and lower thermocline temperatures in sediment core SO18471 (GIK18471), Timor Sea

Paleostudies of the Indonesian Throughflow (ITF) are largely based on temperature and salinity reconstructions of its near surface component, whereas the variability of its lower thermocline flow has rarely been investigated. We present a multi-proxy record of planktonic and benthic foraminiferal d18O, Mg/Ca-derived surface and lower thermocline temperatures, X-ray fluorescence (XRF)-derived runoff and sediment winnowing for the past 130 ka in marine sediment core SO18471. Core SO18471, retrieved from a water depth of 485 m at the southern edge of the Timor Strait close to the Sahul Shelf, sits in a strategic position to reconstruct variations in both the ITF surface and lower thermocline flow as well as to investigate hydrological changes related to monsoon variability and shelf dynamics over time. Sediment winnowing demonstrates that the ITF thermocline flow intensified during MIS 5d-a and MIS 1. In contrast during MIS 5e, winnowing was reduced and terrigenous input increased suggesting intensification of the local wet monsoon and a weaker ITF. Lower thermocline warming during globally cold periods (MIS 4 - MIS 2) appears to be related to a weaker and contracted thermocline ITF and advection of warm and salty Indian Ocean waters.

印度尼西亚贯穿流（Indonesian Throughflow, ITF）的古海洋学研究大多基于其近表层组分的温度与盐度重建结果，而其下层温跃层流的变化则鲜有研究。本研究针对海洋沉积物岩芯SO18471，建立了过去130 ka间的多代理指标记录，涵盖浮游与底栖有孔虫的d18O、Mg/Ca比值反演得到的表层与下层温跃层温度，以及X射线荧光（X-ray fluorescence, XRF）反演的径流量与沉积物簸选数据。该岩芯采自帝汶海峡南缘紧邻萨胡尔陆架、水深485米的站位，其地理位置具备战略优势，既可重建印度尼西亚贯穿流表层与下层温跃层流的变化，也可研究随时间演化的、与季风变化及陆架动力学相关的水文改变。沉积物簸选数据表明，印度尼西亚贯穿流温跃层流在海洋同位素阶段（Marine Isotope Stage, MIS）5d至5a以及MIS 1期间得以增强。与之形成鲜明对比的是，在MIS 5e期间，沉积物簸选强度降低且陆源输入增加，这指示当地湿润季风增强，而印度尼西亚贯穿流则有所减弱。全球冷期（MIS 4至MIS 2）期间的下层温跃层增温现象，似乎与减弱且收缩的温跃层型印度尼西亚贯穿流以及印度洋暖咸水的平流输送存在关联。