Collaborative Research: Detrital Cosmochronology of the Greenland Ice Sheet

合作研究：格陵兰冰盖碎屑宇宙年代学

• 批准号: 0713938
• 负责人: Robert Finkel
• 金额: $ 8.59万
• 依托单位: University of California-Berkeley
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-09-15 至 2011-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0713938&HistoricalAwards=false
• 关键词: Collaborative; Research; Detrital; Cosmochronology; Greenland

ABSTRACTBiermanOPP-0713956FinkelOPP-0713938 Understanding Greenland Ice Sheet (GIS) history to determine when the ice sheet was smaller than today, is critical to understand increased atmospheric CO2 levels and warming climate. The Principal Investigators will associate the previously diminished GIS with other climate and environmental parameters and provide a foundation for predicting its future behavior. The measurement of in-situ-produced cosmogenic nuclides in samples collected from below the ice sheet has the potential to date past episodes of deglaciation through the analysis of isotopic ratios known as burial dating. When the ice cover diminishes, underlying rock and sediment are exposed to cosmic radiation, and radionuclides with differing half-lives (10Be, 26Al, 36Cl and 14C) are produced. When ice returns, exposed surfaces are buried and cosmic rays no longer reach the once-exposed surfaces. The inventory of radionuclides is unsupported by production and begins to diminish by radio-decay; isotopic ratios change predictably because each isotope has a different half-life. Preliminary multi-isotope cosmogenic analysis of rock collected from the bottom of the GISP2 borehole suggests that the summit area was deglaciated about 0.5 ky raising the specter that when climate warms, the ice sheet can disintegrate completely and perhaps not reform. The Principal Investigators will investigate an alternative approach to deep ice coring by studying the products of subglacial erosion and identify when Greenland was ice-free or partially ice-free. The results have the potential to tell us how the GIS responded to intervals of major climate warming over the past several million years.Intellectual Merit: This study will rely on sub-glacial erosion to sample previously-exposed rock surfaces and sediment. It will provide previously unavailable information about the GIS by using isotope ratio analysis to identify past times when the rock and sediment beneath the GIS were exposed to cosmic radiation. Ice flow and englacial drainages deliver sediments to the ice margin where they will collect and analyze clasts directly from outcropping ice. The Principal Investigators will analyze populations of burial ages to determine modes of initial exposure time from which they will infer times of major ice retreat in the past. To interpret isotopic data in glaciological context, they will use existing ice flow and thermal models to infer basal conditions and clast transit histories. Isotopic data will indicate glacial erosion efficiency. Because the penetration depth of most cosmic radiation is only several meters, large numbers of clasts containing no cosmogenic nuclides would indicate efficient sub-ice erosion whereas many clasts with significant burial ages would indicate long subglacial residence times and low rates of bed erosion and sediment transport.Broader Impact: This methodology should have wide application in other areas currently covered by ice. Model ages for GIS shrinkage will provide information for understanding a major driver of sea-level change and have important paleoclimaticimplications. Isotopic data will guide future ice coring efforts, particularly those intended to sample sub-ice rock. Two graduate students will be supported.

AbstractBiermanOpp-0713956finkelopp-0713938了解格陵兰冰盖（GIS）历史记录，以确定冰盖何时小于今天，对于了解增加大气二氧化碳水平和变暖的气候至关重要。主要研究人员将将先前减少的GIS与其他气候和环境参数联系起来，并为预测其未来行为提供基础。通过分析同位素比率的分析称为埋葬日期，从冰盖下方收集的原位生产的宇宙核素的测量可能具有过去的脱气发作。当冰盖减少时，下面的岩石和沉积物会暴露于宇宙辐射中，并产生具有不同半衰期（10BE，26AL，36Cl和14c）的放射性核素。当冰回来时，埋葬的表面被埋葬，宇宙射线不再到达曾经暴露的表面。放射性核素的库存不受生产的支持，并且开始通过无线电减少。同位素比的变化可预测，因为每个同位素都有不同的半衰期。对从GISP2钻孔底部收集的岩石进行的初步多同位素宇宙分析表明，山顶区域被脱落约0.5 ky，升高了幽灵，当气候变暖时，冰片可以完全崩解，也许不是改革。首席研究人员将通过研究冰山侵蚀的产物并识别格陵兰岛何时无冰或部分冰，从而调查一种深层冰芯的替代方法。结果有可能告诉我们GIS在过去几百万年内如何应对主要气候变暖的间隔。智能优点：这项研究将依靠亚冰川侵蚀来样本样品，以样品样本暴露于先前暴露的岩石表面和沉积物。它将通过使用同位素比分析来确定GIS下方的岩石和沉积物暴露于宇宙辐射的过去时，提供先前无法获得有关GIS的信息。冰流和沟渠排水带到冰缘将沉积物传递给他们，他们将直接从露头冰中收集和分析碎屑。首席研究人员将分析埋葬年龄的人群，以确定过去将推断出过去重大冰撤退时间的初始暴露时间的模式。为了解释冰川学环境中的同位素数据，他们将使用现有的冰流和热模型来推断基础条件和碎屑传输历史。同位素数据将表明冰川侵蚀效率。由于大多数宇宙辐射的渗透深度仅为数米，因此没有宇宙核素的大量碎屑表明有效的亚冰侵蚀会表明，许多具有显着埋葬年龄的碎屑表明长期造成的遗传停留时间和较低的床侵蚀率和较低的床侵蚀和沉积物的速度可能会受到层次运输的影响。 GIS收缩的模型年龄将提供信息，以理解海平面变化的主要驱动力并具有重要的古气候刺激性。同位素数据将指导未来的冰芯工作，尤其是那些旨在采样冰岩石的冰芯。将支持两名研究生。