Collaborative Research: Testing Mechanisms for Holocene Climate Change in the Southern Tropical and Mid-Latitude Andes

这项合作赠款正在收集南半球、热带和中纬度地区的古气候代理数据，并使用这些数据来限制全球环流模型(GCM)对气候变化的模拟。通过这种协调努力，这项研究增进了我们对影响小冰期等全新世气候事件的潜在机制的了解。研究人员有三个具体目标：1)利用多种古气候指标，包括湖泊沉积物中的摇摆体和硅藻组合，建立秘鲁最大的热带冰块--奎尔卡亚冰盖附近全新世气候变化的连续记录；2)跟踪安第斯山脉更大范围内(从S纬度约13°到40°)的小冰期气候条件；以及3)使用全球气候模型评估哪些机制假说可以解释重建的古气候波动的地理和时间模式。这项研究建立了奎尔卡亚冰帽附近热带南部全新世古气候和古环境的详细的多指标记录。该年表由放射性碳年龄定义，并辅之以表面暴露(10Be)年龄，可与南北半球的高纬度记录相媲美。除了来自奎尔卡亚的时间上的详细记录外，这项研究还提供了热带南部和中纬度地区小冰期气候的空间分辨率重建。小冰期安第斯冰川在多种气候制度下的广泛波动模式也为研究温度和降水对这种波动的相对影响提供了宝贵的数据。这些工作与美国国家科学基金会正在进行的巴塔哥尼亚全新世冰川波动研究(EAR-0902363)相结合，加强了这两个研究项目。这项研究提供了古气候代理数据和模拟结果，以进一步了解全新世和南热带和中纬度地区的现代气候变化。这项研究测试了小冰河时代的各种机制。例如，它检查了小冰期太阳强迫模型的结果，这些结果表明，除了北半球气候变化外，热带环流也发生了变化。由于奎尔卡亚冰帽附近的古气候数据跨越了受不同边界条件影响的一段时间，例如南半球夏季日照的高低，因此应该有可能研究快速气候事件的各种机制。这项研究的更广泛的影响包括：(1)在一个新的区域(热带安第斯山脉)应用和评估一个有前途的替代(摆动组合)方法，并将沉积物岩心存档；(2)加强和建立科学家之间的新的国际和跨学科合作关系，包括秘鲁的Pedro Tapia博士和智利的科学家；(3)培训研究生和本科生；(4)确保向一般公众传播和传播有关气候变化的信息。

This collaborative grant is collecting paleoclimate proxy data from locations in Southern Hemisphere tropical and mid-latitudes and using these data to constrain global circulation model (GCM) simulations of climate change. Through this coordinated effort, the research enhances our knowledge of potential mechanisms which influenced Holocene climate events such as the Little Ice Age. The investigators have three specific aims: 1) developing a continuous record of Holocene climate change near the largest tropical ice mass, Peru's Quelccaya Ice Cap, using multiple paleoclimate proxies, including chironomid and diatom assemblages in lake sediments; 2) tracking Little Ice Age climatic conditions over a broader area of the Andes, from ~13 to 40°S latitude; and 3) using a GCM to evaluate which mechanistic hypotheses explain the geographical and temporal patterns of reconstructed paleoclimatic fluctuations.This research establishes a detailed multi-proxy record of the Holocene paleoclimate and paleoenvironment in the southern tropics near the Quelccaya Ice Cap. Defined by radiocarbon ages and supplemented by surface exposure (10Be) ages, this chronology is comparable with higher-latitude records from both Northern and Southern Hemispheres. In addition to the temporally detailed record from Quelccaya, the research provides a spatially resolved reconstruction of climate during the Little Ice Age in the southern tropics and mid-latitudes. The broader pattern of Little Ice Age Andean glacier fluctuations in multiple climatic regimes also provides valuable data for examining the relative influences of temperature and precipitation on such fluctuations. These efforts interface with ongoing NSF-funded research (EAR-0902363) investigating Holocene glacier fluctuations in Patagonia, enhancing both research projects.This research provides both paleoclimate proxy data and modeling results to further the understanding of Holocene and recent climate change in the southern tropics and mid-latitudes. The research tests various mechanisms for the Little Ice Age. For example, it examines results from modeling of solar forcing during the Little Ice Age which suggest that there were changes in tropical circulation in addition to Northern Hemisphere climate changes. Since the paleoclimate data from near Quelccaya Ice Cap spans a time period influenced by differing boundary conditions, such as high and low austral summer insolation, it should be possible to examine various mechanisms for rapid climate events. Possible mechanisms include a latitudinal shift of the Intertropical Convergence Zone and the strengthening/weakening of the El Niño Southern Oscillation (ENSO).The broader impacts of the research include (1) applying and evaluating a promising proxy (chironomid assemblages) method in a new area (tropical Andes) and archiving sediment cores; (2) strengthening and establishing new international and interdisciplinary collaborations among scientists including Dr. Pedro Tapia of Peru and Chilean scientists; (3) training graduate and undergraduate students; and (4) ensuring outreach and dissemination to the general public of information regarding climate change.