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

这笔赠款支持对秘鲁跨越全新世(约12ka至今)的山脉冰川进行连续、百年至千年规模的记录的研究，以检验有关热带气候突然变化原因的假设。冰川面粉通量的放射性碳测年和210Pb测年提供了全新世冰川进退的准确年龄和气候突变的记录，使用了秘鲁安第斯山脉中部东西向陡峭的水分梯度上的多个湖泊的冰川湖泊沉积岩芯。冰川面粉的通量是根据多个指标确定的，其分辨率足以与该区域现有的稳定的古气候变异性同位素记录相比较。之前在热带安第斯山脉所做的工作表明，冰川面粉方法可以提供冰川作用的记录，这一记录既与冰川辐射测年记录相一致，也比辐射测年冰川记录更具连续性。这种方法有可能解决一些冰川地质上的不确定性，例如全新世早期冰川推进的时间，以及新冰川期间冰缘波动可能具有的时间超越性。冰川-湖泊方法结合了详细的冰河测绘和有针对性的宇宙源放射性核素测年应用，以从取心地点选择位于山谷上游的全新世冰雹。冰川面粉记录与冰雹年代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-来自不同降水条件下多个流域的冰流模拟为全球尺度环流和古气候模型的动态缩小提供了验证。智力优势和更广泛的影响：将热带冰川质量的变化与气候动力学联系起来是全球气候模拟工作的优先事项，通过准确模拟不同温室情景下过去的变化来预测未来的变化。关于温度和降水变化对热带冰川质量和能量平衡的长期影响，人们仍然知之甚少，主要是因为缺乏来自热带安第斯山脉潮湿和干旱地区的详细和连续的冰川记录。这项工作极大地提高了我们对高山冰川变化、水资源以及地球热带“热机”中的质量和能量通量之间的联系的理解。这些记录对于更好地理解全新世期间高海拔(5000-6000毫升)热带大气变化的时间、幅度和空间范围，以评估低纬水文循环在全球气候突变中的作用是必要的。这将反过来检验以下假设：(1)全新世期间热带安第斯山脉的冰川边缘波动是由南美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隔约1000年至1500年的快速冰期打断(3)热带南部全新世冰川的突然变化(百年至千年尺度)与北半球的变化几乎同步(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)