Collaborative Research: Sonic Logging the NEEM Corehole, Greenland

Past deep ice cores recovered from the Greenland Ice Sheet (GrIS) have failed to obtain intact Eemian ice, ice from the last interglacial period. The recent North Greenland Eemian Ice Drilling effort (NEEM) has successfully recovered ~150 m of such ice. The proposed continuous sonic monitoring of the ice fabric will resolve small scale variability that is missed by the traditional techniques used in thin section analyses of ice cores, which tend to under-sample the core. The scales to be recovered with the sonic sampling are more comparable to those that can be observed with new gas-sampling technologies. The proposed work would add to the physical data set required to fully interpret data being recovered from the NEEM ice core, such as the gas content analyses used to infer past atmospheric conditions. The presence of a special USGS winch this summer, a winch required for the operation of University of Washington instrument proposed for deployment, and the planned abandonment of the NEEM field camp after the summer of 2012, make this proposal appropriate for a RAPID award.此前从格陵兰冰盖（Greenland Ice Sheet, GrIS）中获取的深层冰芯（ice core）均未能获得完整的埃姆间冰期冰体（Eemian ice）——即末次间冰期（last interglacial period）的冰体。近期开展的北格陵兰埃姆间冰期冰芯钻探计划（North Greenland Eemian Ice Drilling, NEEM）已成功获取约150米的该类冰体。本提案拟对冰组构（ice fabric）开展连续声波监测，以此厘清传统冰芯薄片分析（thin section analyses）技术所遗漏的小尺度变化特征；传统薄片分析往往对冰芯采样不充分。声波采样所能获取的尺度，与新型气体采样技术（gas-sampling technologies）所能观测到的尺度更为匹配。本研究工作将完善完整解读NEEM冰芯所获数据所需的物理数据集，例如用于反演古大气环境的气体含量分析。今夏将有一台专属的美国地质调查局（United States Geological Survey, USGS）绞车到位——该绞车是部署华盛顿大学（University of Washington）拟搭载仪器所需的专用设备，加之NEEM野外营地计划于2012年夏季后撤营，因此本提案符合RAPID资助项目（RAPID award）的申请要求。