Millennial-scale palaeoceanographic variability of the North Atlantic through Marine Isotope Stage M2 in the warm mid-Pliocene

本项目将利用孢粉学和有孔虫地球化学资料，研究北大西洋M2期（上新世中期，约3.3 Ma）前后的古海洋变率。海洋同位素阶段（MIS） M2是上新世中期的全球变冷事件，可被视为气候系统转向“第四纪模式”的第一次尝试。初步研究表明，上新世北大西洋的海洋学变化可能在不到一万年的时间尺度上发生。首先，该项目将在MIS M2上建立一个千年尺度的记录，从北大西洋南北样带的四个地点开始。这将验证北大西洋洋流即使在上新世气候变暖的情况下也会突然减弱的假设。此外，样带将有助于评估上新世中期海洋环流与第四纪和现代环流的比较。了解全球气候变暖期间海洋环流的机制与了解地球未来可能的状况高度相关。其次，沿南北样带的地球化学和孢粉数据将反映MIS M2周围不同气候条件和古环境背景的梯度。这对于确定已灭绝的鞭毛类物种的环境偏好至关重要——这是古生态学研究中的一个主要挑战。

The proposed project will apply palynology and geochemical data from foraminifers to investigate the North Atlantic palaeoceanographic variability around Marine Isotope Stage M2 (mid-Pliocene, ca. 3.3 Ma). Marine Isotope Stage (MIS) M2 is a mid-Pliocene global cooling event that can be seen as a first attempt of the climate system to switch into a ‘Quaternary mode’. Preliminary studies have hinted that oceanographic changes in the Pliocene North Atlantic can occur on timescales of less than ten thousand years. Firstly, this project will establish a millennial scale record across MIS M2 from four sites along a north-south transect in the North Atlantic. This will test the hypothesis that the North Atlantic Current can suddenly weaken even during warmer climate conditions of the Pliocene. Furthermore, the transect will allow assessing how mid-Pliocene ocean circulation compares with the Quaternary and present-day circulation. Understanding the mechanisms of ocean circulation during a globally warmer climate is highly relevant for understanding possible future conditions of planet Earth. Secondly, the geochemical and palynological dataset along the north-south transect will reflect a gradient of different climatic conditions and palaeoenvironmental settings around MIS M2. This is essential to identify the environmental preferences of extinct dinoflagellate species – a major challenge in palaeoecological studies.