Evolution of Pliocene-Pleistocene climate and vegetation in the Tropical Andes

上新世，500万至250万年前，通常被认为是最后一次全球气候与今天相似。虽然大气中二氧化碳的浓度与今天相当，但地球的平均温度可能要高出3摄氏度，这就提出了我们的气候系统对二氧化碳变化有多敏感的问题。此外，关于这些温暖的温度如何影响热带地区，包括降水和植被，还有相当多的争论。该项目重建了哥伦比亚热带安第斯山脉在过去500万年中发生的环境变化，以测试全球气候转变，热带环境变化和山脉隆起之间的关系。这一举措加强了美国和哥伦比亚科学家之间的美洲合作，促进了少数民族研究生的职业生涯，早期职业教师，来自低收入家庭和少数民族群体的本科研究助理，并与加州大学自然历史博物馆合作，通过双语活动激励中小学贫困儿童。该项目是第一个整合生物标志物-基于湖泊沉积物和露头中的气候和植被记录，通过重建晚中新世以来热带大陆气候变化。地表温度、植被和水文变化受到分支GDGT、植物蜡及其稳定同位素组成的限制，此外还有保存在波哥大萨瓦纳沉积物中的现有和新的花粉记录。（哥伦比亚）：（a）丰扎二号丰扎湖（~70 ka ~3 Ma）沉积物岩芯：（B）晚中新世-更新世河流和湖泊沉积物露头样品;低海拔地区的晚中新世-上新世早期河流沉积。此外，当代土壤样本沿着东部科迪勒拉的潮湿和干燥的侧翼将被用来产生一个现代的代理校准。该研究为确定中高纬度地区温暖时热带地区是否温暖提供了依据。这一记录将填补上新世以来热带地区过去气候重建的一个空白，并将提供一个全面的气候框架，以更好地解释热带地区的植被变化。该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的知识价值和更广泛的影响审查标准进行评估来支持。

The Pliocene epoch, 5 to 2.5 million years ago, is often cited as the last time global climate resembled that of the present day. While the concentrations of atmospheric CO2 were comparable to those of today, Earth's mean temperature was likely ~3 degrees centigrade warmer, which raises questions about how sensitive our climate system is to CO2 changes. Additionally, there is considerable debate about how these warmer temperatures affected the tropics, including precipitation and vegetation. This project reconstructs environmental changes occurring in the tropical Andes of Colombia over the past 5 million years to test the relationships between global climate transitions, tropical environmental change, and mountain uplift. This initiative enhances Inter-American collaboration among US and Colombian scientists, fosters the career of a minority graduate student, an early career faculty, undergraduate research assistants from low-income families and minority groups, and inspires underprivileged children in elementary and middle schools through bilingual activities in collaboration with the CU Museum of Natural History.This project constitutes the first integration of biomarker-based climate and vegetation records in lake sediment and outcrops by reconstructing continental climate variability in the tropics since the late Miocene. Surface temperatures, vegetation, and hydrological changes are constrained using branched GDGTs, plant waxes, and their stable isotope composition, in addition to existing and new pollen records preserved in sediment from the Sabana de Bogota (Colombia): (a) the Funza II (~70 ka to ~3 Ma) sediment core from the extinct Funza Lake; (b) outcrop samples of Late Miocene-Pleistocene fluvial and lacustrine deposits; and (c) Late Miocene-Early Pliocene fluvial deposits at low-elevation sites. Additionally, contemporary soil samples along the wet and dry flanks of the Eastern Cordillera will be used to produce a modern proxy calibration. This study provides a foundation to determine whether the tropics were warmer when mid and high-latitude regions were warm. Such a record will fill a hole in reconstructions of past climate in the tropics since the Pliocene and will provide a comprehensive climatic framework to better interpret vegetation changes in the tropics.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.