Collaborative Research: Constraining Late Pleistocene Tropical Climates by Dating and Modeling Former Glaciers

该奖项资助合作研究，通过对夏威夷莫纳克亚山和巴布亚新几内亚吉鲁韦山的前晚更新世冰川进行年代测定和建模，重建21000年前末次盛冰期（LGM）的气候。研究人员将检查地球热带地区的冰川冰碛，以更好地了解气候系统对辐射强迫的敏感性。低纬度地区接收到的过量辐射是地球气候系统的一个关键驱动力。这项研究的总体目标是研究地球气候对行星辐射强迫反应的一些基本物理因素，这些因素与目前的情况有很大的不同。冰川冰碛的年代将利用从地表巨石上采集的样本测量的宇宙核素来确定。对于每个区域，从通常被认为代表LGM的冰碛中收集的样本将用3He（氦）和36Cl（氯）来确定年代。为了解决低纬度地区3He的规模和产量问题，该项目包括使用夏威夷放射性碳定年熔岩流进行校准。气候建模将以应用改进的建模策略来重建维持晚更新世热带冰川所需的气候变化的愿望为指导。具体来说，建模工作将使用基于物理的质量和能量平衡冰川模型，该模型已被验证并应用于不同地形和气候环境下的几个冰川。冰川模式考虑了地形阴影、时空变化的反照率、辐射收支的明确处理和湍流通量。这些都是冰川物质平衡的重要控制因素。这项研究很重要，因为它有可能通过提供LGM地区冰川作用的高分辨率年表，提高我们对热带地区基本气候过程的理解，LGM是地球气候制度重要重组的时期。该研究将为两个研究所的研究生提供古气候研究的多学科教育经验。

This award funds collaborative research to reconstruct climate during the Last Glacial Maximum (LGM) at 21,000 years ago by dating and modeling former late Pleistocene glaciers from Mauna Kea, Hawaii, and Mt. Giluwe, Papua New Guinea. The researchers will examine glacial moraines from the Earth's tropics to gain a greater understanding of the sensitivity of the climate system to radiative forcing. Excess radiation received at low latitudes is a key driving force of the Earth's climate system. The overall goal of the research is to examine some fundamental physical elements of the response of Earth's climate to planetary radiative forcing that is significantly different from the present. Glacial moraines will be dated using cosmogenic nuclides measured on samples from surface boulders. For each field area, samples collected from moraines generally thought to represent the LGM will be dated by 3He (helium) and 36Cl (chlorine). To address questions regarding scaling and production rates of 3He at low latitudes, the project includes calibrations using Hawaiian radiocarbon dated lava flows. Climate modeling will be guided by the desire to apply improved modeling strategies to reconstruct the climate change required to sustain late Pleistocene tropical glaciation. Specifically, modeling efforts will use a physically based mass- and energy-balance glacier model that has been validated and applied to several glaciers in different topographic and climatic environments. The glacier model accounts for topographic shading, time and space varying albedo, explicit treatment of the radiation budget, and turbulent fluxes. These are important controls of glacier mass balance.The research is important because it has the potential for improving our understanding of fundamental climate processes in the tropics by providing a high-resolution chronology of glaciation in the region at the LGM, a time of important reorganization of Earth's climate regime. The research will provide a multidisciplinary educational experience in paleoclimate research for graduate students at two institutions.