The tropical rain belt of South America during Plio-Pleistocene cooling

该提案侧重于上新世期间南美洲上空大气环流加强的时间和热带辐合带的位置。上新世的冷却涉及与赤道太平洋温度变化有关的大气环流的加强。太平洋上新世海表温度(SST)记录表明，纬向和经向SST梯度的增加分别加剧了大气Walker环流和Hadley环流。由海洋间盐度散度记录的大西洋和太平洋之间的表层水交换的限制表明，中美洲航道(CAS)的最终关闭发生在4.7-4.2 Ma之间。这次封堵对赤道太平洋环流和赤道东太平洋冷舌的发展产生了强烈影响。CAS的关闭也影响了ITCZ的纬度位置，但模型和数据表明方向相反。该提案旨在利用厄瓜多尔近海ODP1239站点的海洋沉积物，记录上新世南美洲西部赤道和西安第斯科迪勒拉三个关键时期的上新世植被变化。我们的目标是记录南美洲西北部气候和陆地水文的变化，这些变化与ITCZ在4.7到4.2之间的早期移动以及Walker环流在3.6到1.7 Ma之间加强的时间有关。在第一年，我们接近上新世早期。我们可以证明，在CAS关闭期间，ITCZ南移，这与证实其南移假设的数据是一致的。

The proposal focusses on the timing of the atmospheric circulation intensification and the position of the Intertropical Convergence Zone (ITCZ) over South America during the Pliocene. Pliocene cooling involves the intensification of the atmospheric circulation related to temperature changes in the Equatorial Pacific Ocean. Pliocene sea surface temperature (SST) records of the Pacific indicate that increases of the zonal and meridional SST gradients intensified the atmospheric Walker and Hadley circulations, respectively. Restriction of the surface water exchange between the Atlantic and Pacific oceans recorded by the salinity divergence between oceans indicates that the final closure of the Central American Seaway (CAS) occurred between 4.7 and 4.2 Ma. The closure had a strong impact on the circulation in the Equatorial Pacific and the development of the eastern Equatorial Pacific cold tongue. Closure of the CAS also influenced the latitudinal position of the ITCZ, but models and data indicate shifts in opposite directions. The proposal aims at a palynological record of Pliocene vegetation change in west equatorial South America and the western Andean Cordillera for three key periods of the Pliocene using marine sediments of ODP Site 1239 offshore of Ecuador. We aim at a record of changes in climate and terrestrial hydrology of northwest South America related to an early shift of the ITCZ between 4.7 and 4.2 and the timing of the intensification of the Walker circulation between 3.6 and 1.7 Ma. In the first year we approached the early Pliocene period. We could demonstrate that the ITCZ shifted southwards in line with the data confirming the hypothesis of its southward shift during CAS closure.