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

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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.