Northwest African biomes and climate variability during the Pliocene

该项目致力于提高对上新世期间西北非洲气候和植被变化及其驱动力的理解。具体而言，将研究中美洲海道（CAS）关闭导致的翻转环流增强和向北热输送在导致中上新世暖期（MPWP）中热带降雨增加和热带草原林地和森林生物群落扩展的作用。因此，我们将利用ODP站点659的沉积物，该站点位于理想位置，可以记录大草原-森林过渡过程中风沙传输的信号。通过对植物蜡的D/H分析，利用脂质散射13C分析得到的C4草扩展（现代草原生物群系的出现）的信息，重建过去的降雨变率。同时，海洋孢粉学将提供植被组成的详细信息，使生物群落重建成为可能。现有的尘埃通量和深海环流变化记录将用于比较。3.6-3.0 Ma将在千禧年尺度分辨率下进行研究。在第三年，这些分析将扩展到CAS关闭之前的时间间隔（4.9- 4.6 Ma），在没有这些强迫因子的情况下，向北的热输送减少，没有北半球冰盖，以探测气候和植被的变化。

This project strives for a much improved understanding of the variability of climate and vegetation in Northwest Africa and its driving forces during the Pliocene. Specifically, the role of enhanced overturning circulation and northward heat transport due to closure of the Central American Seaway (CAS) in causing the Mid-Pliocene Warm Period (MPWP) with increased tropical rainfall and extension of savannah woodland and forest biomes will be investigated. Therefore, we will utilize sediments from ODP Site 659, located ideally to record aeolian-transported signals from the savannah-forest transition. Past rainfall variability will be reconstructed by D/H analyses on plant waxes with information on the expansion of C4 grasses (emergence of the modern savannah biome) from lipid 13C analyses. In conjunction, marine palynology will provide detailed information on vegetation composition enabling biome reconstructions. Existing records of dust flux and deep-ocean circulation changes will be used for comparison. The period 3.6-3.0 Ma will be investigated in millennial-scale resolution. In the 3rd year, these analyses will be extended to the interval preceding the CAS closure (4.9- 4.6 Ma) with reduced northward heat transport and without Northern Hemisphere ice sheets to detect climatic and vegetation variability without these forcing factors.