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来自南半球热带和中纬度地区的古气候代理数据，并使用这些数据来约束全球环流模型（GCM）对气候变化的模拟。通过这种协调的努力，这项研究增强了我们对影响全新世气候事件（如小冰期）的潜在机制的了解。研究人员有三个具体目标：（1）利用多种古气候代用指标，包括湖泊沉积物中的摇蚊和硅藻组合，在最大的热带冰团--秘鲁的奎尔卡亚冰帽--附近建立全新世气候变化的连续记录;（2）跟踪安第斯山脉更广泛地区（南纬13 °至40°）的小冰期气候条件;（3）利用GCM方法，对重建的古气候波动的地理和时间格局进行了分析，建立了南部热带地区Quelccaya冰帽附近全新世古气候和古环境的多指标记录。定义的放射性碳年龄和补充表面暴露（10 Be）年龄，这年表是可比的高纬度记录从北方和南半球。除了Quelccaya的时间详细记录外，该研究还提供了南部热带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条件下的波动的更广泛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。这些努力与正在进行的NSF资助的研究（ESTA-0902363）调查巴塔哥尼亚全新世冰川波动接口，加强两个研究项目。这项研究提供了古气候代用数据和建模结果，以进一步了解全新世和最近的气候变化在南部热带和中纬度地区。这项研究测试了小冰河时期的各种机制。例如，它研究了小冰期期间太阳强迫模拟的结果，这些结果表明，除了北方气候变化外，热带环流也发生了变化。由于Quelccaya冰帽附近的古气候数据跨越不同的边界条件，如高和低的南半球夏季日射的影响的时间段，它应该有可能检查快速气候事件的各种机制。可能的机制包括热带辐合带的纬向移动和厄尔尼诺南方涛动（ENSO）的加强/减弱。（摇蚊组合）方法（热带安第斯山脉）和沉积物岩心存档;（2）加强和建立包括秘鲁的Pedro Tapia博士和智利科学家在内的科学家之间的新的国际和跨学科合作;（3）培训研究生和本科生;（4）确保向公众宣传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.