中更新世气候转型期印尼穿越流古海洋学记录及其意义

The Mid-Pleistocene Transition (MPT), in the duration of which the dominant periodicity of global climate shifted from 41 kyr to 100 kyr, still remains enigmatic on its mechanisms to folks by so far. As the key component of the global thermohaline circulation in the low latitudes, the Indonesian Throughflow (ITF) significantly affects the climate change over the low latitudes and subsequently on the globe. It is however unclear how the ITF evolved and what its climatic significance was through the MPT. To provide a better understanding of the changing ITF during the MPT, we design this study based on sediments from Site U1483 retrieved during the ‘International Ocean Discovery Program’ Expedition 363 in the Timor Sea, the main exit of the ITF. We will recover paleoceanographic records of the ITF in a time length covering the period of the MPT based on stable isotope and Mg/Ca analyses on shells of surface and subsurface dwelling planktonic foraminiferal species. The target of this study is set to decipher the possible mechanisms of the MPT from the perspective of changing low latitudes thermohaline circulation.

伴随着中更新世气候转型，全球气候主导周期从41kyr转变为100kyr，但转型的机理迄今仍是不解之谜。印尼穿越流作为全球温盐环流在低纬海区的关键组成部分，对低纬海区乃至全球气候变化有着重要影响，其在中更新世气候转型期的古海洋学演化过程和古气候意义也并不清晰。鉴于此，本项目拟以“国际大洋发现计划”第363航次在印尼穿越流的主要出口——帝汶海区获取的U1483站柱状沉积物为材料，分析浮游有孔虫表层种和温跃层种壳体的氧同位素和Mg/Ca比值，重建中更新世气候转型期印尼穿越流的古海洋学演化过程，尝试从低纬海区温盐环流的角度探讨中更新世气候转型的可能机理。

伴随着中更新世气候转型，全球气候主导周期从4万年转变为10万年，但转型的机理迄今仍是不解之谜。印尼穿越流作为全球温盐环流位于低纬海区的关键组成部分，对低纬海区乃至全球气候变化有着重要影响，因此开展中更新世气候转型期印尼穿越流古海洋学研究对于解析中更新世气候转型的机理具有重要意义。本项研究通过对钻取于印尼穿越流区的岩芯进行研究，并与已有的古海洋和古气候记录进行对比，在中更新世气候转型机理及中更新世气候转型结束后印尼穿越流水文演变等方面取得了重要进展，主要进展如下：（1）发现中更新世气候转型期印尼穿越流温跃层海水温度降低所引起的北半球冰盖增加，可能是中更新世气候转型的主要诱因。（2）发现过去40万年间印尼穿越流区降雨在岁差周期上的变化受岁差驱动的热带辐合带纬向范围上膨胀/收缩的影响，在斜率周期上的变化受斜率驱动的热带辐合带南北迁移调控。（3）发现过去12万年间岁差驱动的类厄尔尼诺-南方涛动气候态的状态和热带辐合带的变化是控制印尼穿越流上部水体水文演化的重要因素。