Collaborative Research: RUI: Tropical Holocene climatic insights from Andean paleoglacier dynamics

该补助金支持在秘鲁跨越全新世（~12 ka至今）的山区冰川作用的连续，百年到千年规模的记录，测试有关热带气候突变原因的假设的研究。放射性碳和210铅测年的冰川粉流量提供了精确的全新世冰的进步/退缩和记录的突然的气候转变，使用多个湖泊的冰前湖沉积物岩心沿着陡峭的东西部横跨秘鲁中部安第斯山脉的水分梯度。冰川粉的通量是根据多个代理的分辨率足以使现有的稳定同位素记录的古气候变化从该地区进行比较。以前在热带安第斯山脉的工作表明，冰川粉的方法可以提供一个冰川作用的记录，这是一致的，而且比放射性测年的冰碛记录更连续。这种方法有可能解决几个冰川地质的不确定性，如全新世早期冰川进展的时间，和可能的时间海侵性质的冰缘波动在新冰期。冰川湖泊的方法是再加上详细的冰碛测绘和有针对性的应用宇宙成因放射性核素测年，选择全新世冰碛位于山谷的取芯地点。冰川粉记录与日期冰碛的战略配对提供了冰缘变化的时间和幅度。逆冰川质量平衡-冰流模拟从多个流域在不同的降水制度提供了验证的全球尺度的环流和古气候models.Intellectual优点和更广泛的影响的动力学降尺度：热带冰川质量的变化与气候动力学的关系是全球气候模拟工作的一个优先事项，以预测未来的变化，准确地模拟过去的变化在不同的温室气体情景下。对温度和降水变化对热带冰川质量和能量平衡的长期影响仍然知之甚少，主要是因为缺乏来自热带安第斯山脉潮湿和较干旱地区的详细和连续的冰川记录。这项工作大大提高了我们对高山冰川变异性、水资源以及地球热带“热机”中的质量和能量通量之间联系的理解。需要这些记录来更好地了解冰川活动的时间、量级、高海拔的空间范围（5000 - 6000 masl）全新世期间热带大气变化，以评估低纬度水文循环在全球气候突变中的作用。这反过来将使以下假设的检验成为可能：（1）全新世期间热带安第斯山脉的冰川边缘波动是由南美洲夏季风强度的变化驱动的（2）全新世冰川变化的广泛区域模式被每1000到1500年的快速冰前进周期打断（3）南部热带的突然（百年到千年尺度）全新世冰川变化与北方半球的冰川变化几乎同步（即小冰期）

This grant supports research generating continuous, centennial to millennial-scale records of mountain glaciation in Peru spanning the Holocene (~12 ka to present) that tests hypotheses concerning the causes of abrupt climate change in the tropics. Radiocarbon and 210Pb dating of glacial flour flux provides precise ages of Holocene ice advances/retreats and records of abrupt climatic transitions, using proglacial lake sediment cores from multiple lakes along the steep East-West moisture gradient across the central Peruvian Andes. The flux of glacial flour is determined based on multiple proxies at a resolution sufficient to enable comparison with existing stable isotope records of paleoclimate variability from the region. Previous work in the tropical Andes demonstrates that the glacial-flour approach can provide a record of glaciation that is both consistent with and far more continuous than radiometrically-dated moraine records. This approach has the potential to resolve several glacial geologic uncertainties, such as the timing of early Holocene glacial advances, and the possible time-transgressive nature of ice margin fluctuations during the neoglacial. The glacial-lacustrine approach is coupled with detailed moraine mapping and the targeted application of cosmogenic radionuclide dating to select Holocene moraines located up-valley from coring localities. The strategic pairing of glacial flour records with dated moraines provides both the timing and magnitude of ice margin changes. Inverse glacier mass balance-ice flow simulations from multiple watersheds in different precipitation regimes provide validation for the dynamical down-scaling of global-scale circulation and paleoclimate models.Intellectual Merits and Broader Impacts: Relating the changes in tropical glacier mass to climate dynamics is a priority for global climate modeling efforts to predict future changes based on accurately simulating past changes under different greenhouse scenarios. The long-term perspective of temperature and precipitation changes on tropical glacier mass and energy balance is still poorly understood, primarily because of a lack of detailed and continuous glacial records from both the humid and more arid parts of the tropical Andes. This work substantially improves our understanding of the link between alpine glacial variability, water resources and mass and energy fluxes in the tropical "heat engine" of the planet.These records are needed to better understand the timing, magnitude, and spatial extent of high elevation (5000 - 6000 masl) tropical atmospheric change during the Holocene to evaluate the role of the low latitude hydrologic cycle in abrupt global climatic shifts. This, in turn, will enable testing of the following hypotheses:(1) Glacier margin fluctuations in the tropical Andes during the Holocene were driven by changes in the strength of the South American Summer Monsoon(2) A broad regional pattern of Holocene glacial variability was punctuated by periods of rapid ice advances every ~1000 to 1500 years(3) Abrupt (centennial to millennial-scale) Holocene glacier variations in the southern tropics were nearly synchronous with those in the Northern Hemisphere (i.e. The Little Ice Age)