Central American climates of the last interglacial

过去的间冰期为我们提供了对气候和生态系统极端事件的反应的见解，这些极端事件超出了全新世的范围。虽然不是预测气候变化的完美类比，但海洋同位素阶段5e（MIS 5e）等间冰期为我们提供了可能更温暖和更干燥条件下的最佳经验见解。因此，国际上正在作出重大努力，从格陵兰捕获MIS 5e，并对从所有纬度获取高分辨率记录有广泛的兴趣。除了简单地想知道间冰期条件外，古气候学界对进入和离开间冰期条件的过渡特别感兴趣，即终止II和开始I。该项目提供了百年尺度的多代理分析终端II，MIS 5e和d（135-106 ka）从三个最近收集的沉积物岩心从墨西哥，危地马拉和巴拿马。这些记录构成了MIS 5e在新热带地区气候和植被变化的第一个详细的陆地档案。分析包括XRF，岩心颜色，化石花粉，木炭和硅藻分析。每个遗址的年代学是通过地质年代学和U系测年相结合建立的。巴拿马岩芯的初步铀系测年结果证实，在130 ~ 115 ka之间有近5 m的沉积。其他记录似乎有类似或更快的沉积速率。贝叶斯统计用于创建温度、降水量和每年干旱天数的传递函数。这些数据被用来测试假设有关的热带辐合带的过去的迁移，不同强度的纬向翻转环流，准周期的气候节奏的存在下，和MIS 5e相对于全新世的变化。这提供了第一个区域估计是否过去的间冰期是一个时间的森林或灌木丛扩张在中美洲，这一发现是至关重要的建模过去和未来的碳storage.This数据提供了重要的基准，对古气候模型可以进行测试。目前，中美洲或墨西哥没有关于MIS 5e的详细地面数据。这些数据对那些从事农业、林业或自然保护规划的人具有重要意义。提供中美洲高分辨率的气候记录可以检验其他记录中产生的假设，这些数据对研究现代森林动态的生态学家和研究热带多样性起源的进化生物学家也具有重要意义。为这些核心提供清晰的年表鼓励其他工作人员使用不同的代理来处理它们。这项研究导致了墨西哥、美国、德国、哥斯达黎加和英国大量的新合作。在该项目期间，每年培训两名本科生，并鼓励REU和RET人员发表他们的成果。一个博士学生和一名博士后。哥斯达黎加的一名女硕士学生参与了该项目，没有向国家科学基金会收取任何费用。

Past interglacials offer us insights into the response of climate and ecosystems extremes beyond those experienced within the Holocene. While not perfect analogs for projected climate change, interglacials such as Marine isotope stage 5e (MIS 5e) offer us the best empirical insights available for probably warmer and drier conditions. Consequently, a substantial international effort is being made to capture the MIS 5e from Greenland and there is broad interest in acquiring highly-resolved records from all latitudes. Beyond simply wanting to know interglacial conditions, the paleoclimatic community is particularly interested in the transitions into and out of interglacial conditions, i.e. Termination II and Inception I. This project provides centennial-scale multiproxy analyses for Termination II, and MIS 5e and d (135-106 ka) from three recently collected sediment cores from Mexico, Guatemala, and Panama. These records form the first detailed terrestrial archive of climate and vegetation change for MIS 5e from the Neotropics.The analyses include XRF, core color, and fossil pollen, charcoal and diatom analyses. A chronology for each site is established through a combination of tephrachronology and U-series dating. Preliminary U-series dates from the Panamanian core confirms almost 5 m of deposition between ages of 130 and 115 ka. The other records appear to have similar or faster rates of deposition. Bayesian statistics are used to create transfer functions for temperature, precipitation, and number of dry days per year. These data are used to test hypotheses relating to the past migration of the inter-tropical convergence zone, varying strength of the meridional overturning circulation, the presence of quasi-cyclic climatic rhythms, and the variability of MIS 5e relative to the Holocene. This provides the first regional estimate of whether the past interglacial was a time of forest or scrubland expansion in Central America, a finding that is of critical importance to modeling past and future carbon storage.This data provides important benchmarks against which paleoclimate models can be tested. Currently, no detailed terrestrial data are available for MIS 5e from Central America or Mexico. This data is of significance to those engaged in planning for a warmer world, whether for agriculture, forestry or conservation. The provision of highly resolved climate records from Central America allows hypotheses generated in other records to be tested.This data is also of significance to ecologists studying modern forest dynamics and to evolutionary biologists investigating the origins of tropical diversity. Providing well-resolved chronologies for these cores encourages other workers using different proxies to work on them.This research leads to a significant number of new collaborations in Mexico, the USA, Germany, Costa Rica, and the UK. During this project two undergraduates are trained each year, and REU and RET personnel are encouraged to publish their results. One Ph.D. student and one post-doc are supported. A female MS student in Costa Rica is engaged in the project without charge to NSF.