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620 ka以来帝汶海西南部表层海水温盐变化及其影响因素
崔亦鹍
Subtype硕士
Thesis Advisor常凤鸣
2020-06
Degree Grantor中国科学院大学
Place of Conferral中国科学院海洋研究所
Degree Name工程硕士
Keyword印度尼西亚穿越流 剩余海水氧同位素 海表温度 沉积物捕获器
Abstract

印度尼西亚穿越流(Indonesian ThroughflowITF)控制了印度洋和太平洋间的水体与热量交换,显著影响着现代印太地区的气候和海洋环境,且在过去的区域水文条件演变过程中也起了至关重要的作用。目前,有关ITF在轨道亚轨道尺度上的研究多限于末次冰期,对其在多个冰期旋回中的演变缺乏认识。帝汶海是ITF进入印度洋的主要通道之一,本研究利用位于ITF帝汶海出口处的IODP 363航次U1482钻孔(15°3.32ʹS120°26.10ʹE,水深1446 m)样品,通过浮游有孔虫Trilobatus sacculifer壳体的氧同位素和Mg/Ca分析,重建了620 ka以来帝汶海西南部表层海水温度(Sea Surface TemperatureSST)和剩余氧同位素(δ18Osw-iv)的变化。结合西太平洋暖池区、ITF流经区域、中高纬地区的其它记录,分析了近6次冰期旋回中区域表层水体温度和盐度的演变特征,探讨了其可能的影响因素。

620 ka以来,帝汶海西南部的SST呈现冰期低、间冰期高的特征,其演变具有显著的偏心率(100 ka)、斜率(40 ka)和岁差(23 ka19 ka)周期。其中,岁差信号可能主要来自ITF的源区以及其输运过程中季风、热带辐合带(Intertropical Convergence ZoneITCZ)降水对其水体来源、强度和结构的影响。此外,当地太阳辐射、区域风场等局地因素的影响对SST的岁差信号也起到了加强作用。SST的斜率信号可能是来自于斜率控制下厄加勒斯流(Agulhas currentAC)向南大西洋的热量输运和鲁汶流(Leeuwin CurrentLC)向极暖水输送的变化。SST的偏心率信号则主要源自冰期旋回中全球海洋温度变化在低纬地区的响应。

620 ka以来帝汶海西南部,与海表盐度正相关的δ18Osw-iv呈现出冰期低、间冰期高的特征,且其变化具有显著的岁差(23 ka)和斜率(40 ka)周期。分析表明,研究区盐度受当地大气降水及河流输入影响较小,更多的是受ITF结构、强度以及海平面升降等因素的控制。岁差驱动下盛行风向的变换和ITCZ南北位移导致的降水强度变化显著影响了ITF结构与强度,从而令δ18Osw-iv呈现出显著的岁差周期。冰期旋回中海平面周期性的升降导致ITF通道连通性发生改变,作用于ITF结构与强度,使得δ18Osw-iv呈现出冰期低、间冰期高的特征。而斜率驱动下南半球经向温度梯度的周期性变化控制了ITF低盐水体通过鲁汶流的向极输运,从而导致研究区δ18Osw-iv呈现出40 ka的斜率周期。

对西太平洋布放沉积物捕获器潜标系统中所遇到的实际问题进行了分析,针对实践中由于样品瓶脱落导致的样品丢失率高(20%左右)的问题,提出在开阔大洋等水动力较强的环境中布放沉积物捕获器时根据当地的洋流环境采取的加固措施并设计了一种样品瓶专用固定装置,以达到安全回收样品的目的。

Other Abstract

The Indonesia Throughflow (ITF), which regulates the water and heat exchange between the Pacific Ocean and Indian Ocean, has significant influence on the recent climate and environments in the Indo-Pacific region. Also, it exerted a crucial role in the evolution of regional hydrological conditions during the past times. However, most of the existing researches on the changes of ITF in geological history are limited to the last glacial period with insufficient knowledge on its evolution over multiple glacial cycles. International Ocean Discovery Program (IODP) Site U1482 (Expedition 363) is within the main path of outflow of ITF at 15°3.32′S, 120°26.10′E and 1466 m below sea level (mbsl). In this study, the upper 42.48 m core composite depth below seafloor (CCSF) of site U1482 was used to reconstruct the sea surface temperature (SST) based on δ18O and Mg/Ca analyses of planktonic foraminifera Trilobatus sacculifer (T. sacculifer), and thus to investigate the variations in the seawater residual oxygen isotope (δ18Osw-iv) over the past 620 ka. Combined with other paleoclimate records from the Western Pacific Warm Pool (WPWP), ITF pathway and mid-high latitudes, the characteristics of temperature and salinity changes in the multiple glacial cycles were analyzed to reveal the possible factors that determine their changes.

The SST record shows a clear character, with higher and lower values during the interglacial and the glacial, respectively. Spectral analysis of the SST reveals that spectral power concentrate in the precession (23 ka, 19 ka) period, obliquity (41 ka) period and eccentricity (100 ka) period. The precession signal may come from the ITF source area and its transportation process. When Asian monsoon and precipitation caused by the Intertropical Convergence Zone (ITCZ) significantly affected the intensity and structure of the ITF. Also, the local factors, such as insolation and prevailing wind direction alternation have strengthened the precession signal of SST. The periodic variations in the intensity of the Agulhas current (AC), which controls the heat transfer from the Indian Ocean to the South Atlantic, and the warm poleward ocean southwards Leeuwin Current (LC) resulted in the obliquity signal of SST in the study area. The eccentricity cycle characteristics of the SST are mainly origin from the response of the region SST to periodic changes of global sea surface temperature during the glacial cycle.

The variability of δ18Osw-iv, which has a positive correlation with sea surface salinity (SSS), shows significant precession (23 ka) and obliquity (40 ka) cycles, with higher values during the interglacial over the past 620 ka. Analysis shows that the δ18Osw-iv characteristics of the study area are less affected by local atmospheric precipitation and river input, but more affected by the factors, such as the changes of ITF structure and intensity and global sea level fluctuations. The periodic alternations of prevailing wind and the meridional migrations of the ITCZ driven by precession could influence the structure and strength of the ITF, and then the salinity in the southwest of the Timor Sea. The glacial cycles of the δ18Osw-iv record coincides with the periodic onset of deglaciation, indicating the considerable role of the global sea level fluctuations in the regional hydrology during the glacial cycle that determined the connectivity of the ITF channels among the Indonesian archipelagos. The variations in the meridional temperature gradient in the southern hemisphere driven by the obliquity of the earth's orbit could also affect the southward transport of the ITF fresh water to the high latitude areas and caused the δ18Osw-iv in the study area to exhibit obliquity period of 40 ka.

This study also analyzes the practical problems encountered in the deployment of mooring systems equipped with sediment traps in the Westernest Pacific and gives a solution for the issue. For the issue of high sample loss rate (about 20%) due to sample bottle dropping, a reinforcement measure based on the local ocean current circumstances is presented for the deployment of sediment trap system in the open ocean with powerful hydrodynamic conditions. And, a special fixing cable-tie for the fastening of sediment sample bottles to protect sample bottles from losing was designed to achieve the purpose of safe recovery of samples.

MOST Discipline Catalogue工学::地质资源与地质工程
Language中文
Document Type学位论文
Identifierhttp://ir.qdio.ac.cn/handle/337002/164714
Collection海洋地质与环境重点实验室
Recommended Citation
GB/T 7714
崔亦鹍. 620 ka以来帝汶海西南部表层海水温盐变化及其影响因素[D]. 中国科学院海洋研究所. 中国科学院大学,2020.
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620 ka以来帝汶海西南部表层海水温盐(8160KB)学位论文 暂不开放CC BY-NC-SA
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