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，填补稀少的水文气候记录，以及更全面地了解气候变异性。与南美同事的合作以及广泛的学生参与都是计划中的。该项目旨在利用经典的树木年代学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分解并绝对过时。放射性碳测量(14碳)将确保准确的测年评估。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系列将被用来重建过去几个世纪的气候变化和区域到大范围的大气动力学。该项目的具体目的是提高对以下问题的认识：(1)南美洲夏季风的时空变异性；(2)厄尔尼诺-南方涛动(ENSO)与南美洲夏季风之间的长期相互作用；(3)火山强迫对热带安第斯山脉过去水文气候的影响。虽然树轮在温带气候中得到了广泛的应用，但热带地区仍然相对未被开发，因为特别是很难确定与季节或年度生长期相对应的一致的木层(树轮)。中央安第斯山脉是克服这些困难的理想地区，因为明显的降水季节性和多样化的森林。热带安第斯山脉是生物多样性的热点，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，最近广泛的冰川消退正在导致水文储量的迅速下降。这一下降，再加上人口增长和经济扩张导致的水需求增加，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气候具有强烈的地带性和垂直性降水梯度。来自热带大西洋和亚马逊盆地的水汽流入受到SASM和ENSO的调制。对这种变异性的科学理解受到长期仪器观测匮乏的挑战，这也限制了限制该地区未来气候变化预测中的不确定性的能力。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.