Collaborative Research: P2C2--Reconstructing South American Monsoon Sensitivity to Internal and External Forcing: Reconciling Models and Tree-ring Proxies in the Central Andes

潜在的更广泛的影响包括有可能更好地了解南美季风，填补稀疏的水文气候记录，以及更充分地了解气候变率。计划与南美同事合作，广泛的学生参与。该项目旨在采用经典的树木年轮技术来生成新的热带树木年轮年表，这些年轮年表每年都会被确定并确定年代。放射性碳测量（14-碳）将确保准确的定年评估。因此，将选择成功的树种来改善南半球的14-碳曲线。由此产生的树木年轮序列将用于重建过去几个世纪的气候变率和区域到大尺度的大气动力学。该项目的具体目标是提高对以下方面的认识：(1)南美洲夏季风（SASM）的时空变异性；(2) El Niño-Southern涛动（ENSO）与SASM的长期相互作用；③火山强迫对热带安第斯山脉过去水文气候的影响。这项研究的目的是通过在秘鲁和玻利维亚的热带安第斯山脉建立一个树木年轮网络，为热带树木年代学科学提供重大进展，这一地区的高分辨率陆地古记录覆盖率非常低。虽然树木年轮已在温带气候中广泛使用，但由于难以确定与季节或年度生长期相对应的一致的木材层（树木年轮），热带地区仍然相对未被探索。安第斯山脉中部是克服这些困难的理想地区，因为这里有明显的降水季节性和多样的森林。热带安第斯山脉是生物多样性的热点地区，其地理位置使其极易受到气候变化的影响。它还包含了地球上几乎所有的热带冰川，最近，广泛的冰川退缩正在导致水文储备的迅速减少。这种下降，再加上人口增长和经济扩张导致的用水需求增加，对水资源供应、生物多样性和粮食安全构成了巨大挑战。安第斯科迪勒拉复杂的地形导致了以强烈的纬向和垂直降水梯度为特征的气候。来自热带大西洋和亚马逊盆地的水汽流入受到SASM和ENSO的调节。由于缺乏长期仪器观测，对这种变率的科学认识受到了挑战，这也限制了约束该地区未来气候变化预估不确定性的能力。该奖项反映了美国国家科学基金会的法定使命，并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，被认为值得支持。

The potential Broader Impacts include the potential for better understanding the South American monsoon, for filling in sparse hydroclimate records, and for fuller understanding climate variability. Collaboration with South American colleagues is planned as is extensive student involvement.This project aims to employ classical dendrochronological techniques to generate new tropical tree-ring chronologies that are annually resolved and absolutely dated. Radiocarbon measurements (14-Carbon) will ensure accurate dating assessments. Thus, successful tree species will be selected to improve the 14-Carbon curve for the Southern Hemisphere. The resulting tree-ring series will be used to reconstruct past climate variability and regional to large--scale atmospheric dynamics for the last several centuries. The specific aims of the project are to improve understanding of: (1) the spatiotemporal variability of the South American summer monsoon (SASM); (2) long-term interactions between El Niño-Southern Oscillation (ENSO) and the SASM; and (3) the impact of volcanic forcing on past hydroclimate of the tropical Andes.The research aims to provide significant advances in the science of tropical dendrochronology bydeveloping a tree-ring network for the tropical Andes in Peru and Bolivia, a region with exceedingly scarce coverage of high-resolution terrestrial paleo-records. While tree rings have been extensively used in temperate climates, the tropics remain relatively unexplored due to the difficulty, in particular, of identifying consistent wood layers (tree rings) corresponding to seasonal or annual growing periods. The Central Andes are an ideal region for overcoming these difficulties, due to the pronounced precipitation seasonality and diverse forests.The tropical Andes are a hotspot for biodiversity and its geographic position makes it extremely vulnerable to climate change. It also contains nearly all the tropical glaciers on the globe, and recent, widespread glacial retreat is causing a rapid decline in hydrological reserves. This decline, in combination with increasing water demand due to population growth and economic expansion poses an enormous challenge for water availability, biodiversity and food security. The complex topography of the Andean Cordillera leads to a climate that is characterized by strong zonal and vertical precipitation gradients. Moisture influx from the tropical Atlantic Ocean and the Amazon basin is modulated by the SASM and ENSO. The scientific understanding of this variability is challenged by the scarcity of long instrumental observations, which also limits the ability to constrain uncertainties in future climate change projections over this region.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.